Gathered up some recommended antennas, boosters, etc... for OTA HDTV reception:

Antennas
A-Tech custom assembly - w/ 2 Blake JBX21WB high gain yagi UHF antennas (http://www.atechfabrication.com/information/what_is_the_best_antenna_system.htm)
ATF-X300 Precision Antenna - horizontal dual yagi array (http://www.atechfabrication.com/products/atfx300_precision_antenna.htm)
Antiference XG16EW - horizontal dual yagi array (http://www.antiference.co.uk/extra.htm)
Blake JBX21WB high gain yagi UHF (Blake UK) (https://ssln2.aldenhosting.com/~n2hd4fre/)
Blake JBX21WB high gain yagi UHF (Blake UK) (http://www.blake-uk.com/downloads/UHF%20TV%20Aerials/High%20Gain%20JBX%20Leaflet.pdf)
Blonder Tongue BTY Series VHF & UHF antennas (http://www.blondertongue.com/Reception) 9/1/05
Antennas Direct 91XG Uni-Directional Antenna - yagi UHF (http://www.antennasdirect.com/91XG_HDTV_Antenna.html)
Televes DAT75 Digital Wideband Tv Aerial - yagi UHF (http://www.tlc-direct.co.uk/Products/MXDAT75.html)
Triax Unix 100 element aerial - yagi UHF (http://www.triax.co.uk/Products/Aerials/UHF%20Aerials/Unix%20Aerials.aspx?productId)
Antiference DX8W - yagi UHF (http://www.antiference.co.uk/dx8.htm)
Winegard PR-9032 yagi UHF (http://www.starkelectronic.com/wpr9032.htm)
Channel Master Model 4248 aka 3023 yagi UHF (http://www.starkelectronic.com/cmant.htm)
Winegard HD-9095P yagi UHF (http://www.tvantenna.com/products/tvreception/tvantennas/winegard/HD-9095P.html)
Funke DC.4591-21/69 yagi UHF (http://www.mondoplast.ro/ft/DC.4591-21-69.html)
Home page for Funke aerial antennas (http://www.funke.nl/)

Channel Master CM 4228 - 8-bay bowtie UHF (http://www.pctinternational.com/channelmaster/antennas_outdoor_uhf.html)
Antennas Direct DB2 - 2-bay double bowtie indoor UHF (http://www.antennasdirect.com/DB2_Indoor_antenna.html)
Antennas Direct DB4 - 4-bay bowtie UHF (http://www.antennasdirect.com/DB4_HDTV_antenna.html)
Antennas Direct DB8 - 8-bay bowtie UHF (http://www.antennasdirect.com/DB8_HD_Antenna.html)
Pro Brand International - 2-bay double bowtie indoor UHF (http://www.eagleaspen.com/products/products_1.php?id=49)
Radio Shack UHF Dual HDTV Indoor Antenna - 2-bay double bowtie indoor UHF (http://www.radioshack.com/sm-uhf-dual-hdtv-indoor-antenna--pi-2103058.html)
Winegard Square Shooter (SS-1000 & SS-2000) - indoor/outdoor UHF (http://www.winegard.com/offair/squareshooter.htm)
Antiference/Zenith Silver Sensor - indoor UHF (http://www.zenith.com/sub_prod/product_Display.asp?cat=49&id=131)
Kathrein Scala PR-TV Paraflector parabolic UHF (http://www.kathrein-scala.com/uhf-tv_parabolic.php) 8/15/06
Wade 4' parabolic UHF antenna (http://www.wade-antenna.com/Wade/uhfparabolic.pdf) 4/12/07
Wade 6' parabolic UHF antenna (http://www.wade-antenna.com/Wade/uhfparabolic.pdf) 4/12/07
Wade 8' parabolic UHF antenna (http://www.wade-antenna.com/Wade/uhfparabolic.pdf) 4/12/07

Rotors, tilters...
ATF-V300 Precision Tilter (http://www.atechfabrication.com/products/atfv300_vertical_tilter.htm)
ATF-V200 Economy Tilter (use w/Channel Master 9521A rotator) (http://www.atechfabrication.com/products/atfv200_economy_tilter.htm)
Channel Master Model 9521A horizontal rotator (http://www.channelmaster.com/Pages/TVS/Rotators.htm)
ARS Antenna Rotator System for PC (http://www.ea4tx.com/products/ars-rotators.htm)
Eagle Aspen ROTR100 rotor (http://eagleaspen.com/products/products_1.php?id=90) 4/12/07
Eagle Aspen ROTR100 rotor test (http://www.avsforum.com/avs-vb/showthread.php?t=840847) 5/12/07
hy-gain rotators (http://www.hy-gain.com/products.php?catid=8)
Yaesu rotators (http://www.yaesu.com/?cmd=DisplayProducts&DivisionID=65&ProdCatID=104)

Preamplifiers/boosters
Angle Linear PHEMT single stage preamplifier - to 20 dB, .4 dB noise (http://www.anglelinear.com/gaasfet/gaasfet.html)
Research Communications Type 9250 HDTV PHEMT LNA - 20 dB, .4 dB noise (http://www.researchcomms.com/hdtv.html)
Research Communications Type 9248 TV LNA (75 ohms) - 20 dB, .4 dB noise (http://www.researchcomms.com/television.html)
Winegard AP-4700 UHF Pre-amplifier - 19 dB, 2.9 dB noise (http://www.winegard.com/offair/pdf/Chart29.pdf)
Winegard AP-8275 UHF Pre-amplifier - VHF 28 db, 2.8 noise UHF 29 dB, 2.9 dB noise (http://www.winegard.com/offair/pdf/Chart29.pdf)
Channel Master CM-7775 preamp - 26 dB, 2.0 dB noise (http://www.pctinternational.com/channelmaster/amplifiers.html)
Channel Master CM-7777 preamp - VHF 23 db, 2.8 noise UHF 26 dB, 2.0 dB noise (http://www.pctinternational.com/channelmaster/amplifiers.html)
Kuhne Electronic broadband UHF PHEMT preamplifier - 20 dB, 1.2-2 dB noise (http://www.kuhne-electronic.de/english/preamplifier/broadband.htm)
Sitco PA24 Series UHF preamplifier - 25 dB, 1.4 dB noise (http://www.simplicitytool.com/preamplifier.htm)
Radio Shack 15-2507 - 15 dB each main amp & preamp, <4.5 dB noise (http://www.radioshack.com/sm-tv-hdtv-vcr-fm-antenna-mounted-high-gain-signal-amplifier--pi-2103094.html)

Accessories hyperlinked 6/10/05
Blake non-penetrating roof mount (http://www.blake-uk.com/prod_products_installation_standard_satellite_patio_mounts.a spx)
Antenna mount, side wall installation (http://www.blake-uk.com/serv_installation_options_wallinstallations.aspx)
CC-5C Multi-conductor control cable (http://www.atechfabrication.com/products/atfv300_vertical_tilter.htm#CC-5C)
Dual Antenna Boom Assembly (http://www.atechfabrication.com/products/dual_antenna_boom.htm)
CB-V300 center boom bracket (http://www.atechfabrication.com/products/dual_antenna_boom.htm#CB-V300)
PH-30B Phasing harness (http://www.atechfabrication.com/products/phasing_harnesses.htm)
Winegard CS-002 5-1000MHz Splitter (http://www.atechfabrication.com/products/phasing_harnesses.htm#signal%20combiners)
Antenna Phasing Harnesses and Signal Combiners (http://www.atechfabrication.com/products/phasing_harnesses.htm)
CA-11Q - cable type "F" male cable connectors (http://www.atechfabrication.com/products/coaxial_cable.htm)
Channel Master Model 1612 - mast 2 - 1.25" x 10' 16 gauge steel mast tubes
Channel Master CM 9014, 9039 Universal Swivel, Steel Base Mounts & hardware

Antenna/reception links
”How to” for television stations wihin the given range of your location (http://www.avsforum.com/avs-vb/showthread.php?p=7625830&&#post7625830)
See broadcast television stations wihin the given range of your location (http://www.2150.com/broadcast/default.asp)
Latitude/longitude finder (http://www.census.gov/cgi-bin/gazetteer)
Magnetic declination - values of time/date/locaton... (http://www.ngdc.noaa.gov/seg/geomag/declination.shtml)
Antennaweb - finding local TV statios/support (http://www.antennaweb.org/aw/Address.aspx)
TitanTV (http://www.titantv.com/quickguide/quickguide.aspx)
DTV Stations on the Air - state map selection (http://www.digitaltvzone.com/dtv_stations_on_air/index.asp)
Worldwide list of Radio & TV Stations (http://www.w9wi.com/) 6/9/05
HDTV Television Channel Broadcast Status (http://www.tvtower.com/hdtv_status.html) 6/9/05
National and Worldwide lists of Broadcast Radio, TV and Ham radio stations (http://www.tvradioworld.com/default.asp) 6/9/05
same site as above - listing California (http://www.tvradioworld.com/region1/ca/) 6/9/05
Very useful site, w/Doug Lung's weekly RF REPORT column on DTV Technology (http://www.tvtechnology.com/) 6/9/05
No more hit-or miss: spectrum analyzers (http://www.hdtvexpert.com/pages/hitormisspf) 9/5/05
The Official AVS Antenna / OTA Reception Topic! (http://www.avsforum.com/avs-vb/showthread.php?t=381623&page=1&pp=30) 9/6/05
Calculators, maps...
Antenna Up/Down Tilt Calculator (compensates for Earth curvature) (http://www.ecommwireless.com/cgi-local/tilt.main.cgi) 6/9/05
Antenna Tilt Angle Calculator (http://weltwireless.home.att.net/tech/antenna_tilt_angle_calculator.html) 6/9/05
Interactive Wireless Network Design Analysis Utilities (http://www.ecommwireless.com/calculations.html) 6/9/05
Antenna - K-Factor & climate effects (http://www.tvtechnology.com/features/On-RF/f-DL-signals.shtml) 6/9/05
Vincenty formula for distance between two Latitude/Longitude points (http://www.movable-type.co.uk/scripts/LatLongVincenty.html) 6/12/05
Vincenty's Formulae, Inverse Method (http://www.ga.gov.au/nmd/geodesy/datums/vincenty_inverse.jsp) 6/14/05
Forward Inverse - Azimuth, distance... ellipsoidal calc program (http://www.mentorsoftwareinc.com/PRODUCTS/FWDINV.HTM) 6/14/05
Ellipsoid Radii Calculator (http://www.mentorsoftwareinc.com/FREEBIE/FREE0999.HTM) 6/14/05
Vincenty Ellipsoid corrected “Great Circle Calculator” (http://williams.best.vwh.net/gccalc.htm) 6/14/05
Distance and bearing between two Latitude/Longitude points (http://www.movable-type.co.uk/scripts/LatLong.html) 6/14/05
Freeware DOS program calculates ellipsoidal geodesic path (http://home.earthlink.net/~rcmcc/) 6/14/05
UHF conversion charts (channel/frequency) - CATV - TV - FM Frequencies (http://www.chem.hawaii.edu/uham/catvfreq.html)
TerraServer.com - motherload of topo & other maps (hi-rez viewing requires subscription) (http://www.terraserver.com/) 6/9/05
GeoCode Eagle will show your GPS LAT/LONG on a Topo Map (http://www.geocode.com/modules.php?name=TestDrive_Eagle) 6/9/05
Tailor coordinates to yield Topo or Aerial Photo Map in jpg format (http://www.lostoutdoors.com/newmap.html) 6/9/05
Free RADIO MOBILE Propagation Prediction Program, holl_and's thread/description... (http://hdtv.forsandiego.com/messages/1/2846.html?1112095186) 6/9/05
Custom topographic maps - free preview (http://www.mytopo.com/index.cfm) 6/8/05
Digital Topo Maps (http://www.digital-topo-maps.com/) 6/8/05
USGS Maps (http://www.usgs.gov/) 6/8/05
TopoZone (http://www.topozone.com/default.asp) 6/8/05
SatCalc - pointing angle for any geosynchronous TV satellite (http://www.nerosoft.com/SatCalcView.asp) 6/8/05
Antenna information
Recommended high gain UHF TV antennas (http://www.geocities.com/toddemslie/UHF-TV-DX.html)
Fox55 antenna selection (http://www.wfxsfox55.com/reception.html)
TV and FM receivers, currently used by Dxers (http://www.geocities.com/toddemslie/dxantennasandreceiverscurrentlyusedbydxers.htm)
TV and FM receivers, currently used by Dxers (http://www.geocities.com/toddemslie/scanners_for_TVDX.htm)
Erecting a TV Antenna & other HDTV Primer links (http://www.hdtvprimer.com/ISSUES/erecting_antenna.html) 6/7/05
Indoor antennas (http://www.hdtvprimer.com/ANTENNAS/GlossaryG.html#indoor)
Comparing the common antenna types (http://www.hdtvprimer.com/ANTENNAS/comparing.html)
Comparing the common antenna types (http://www.hdtvprimer.com/ANTENNAS/types.html)
HEAVY METAL, PART 1 - VHF-UHF Antennas Compared for Outdoor DTV Reception (http://www.svconline.com/mag/avinstall_heavy_metal_part/)
HEAVY METAL, PART 1 - w/pictures (http://www.hdtvexpert.com/pages/antoutsan.htm)
HEAVY METAL, PART 2 - Comparisons of indoor antennas for VHF-UHF DTV reception (http://www.hdtvexpert.com/pages/antin.htm) 6/7/05
LUXORION - LOTS of Antenna systems info (links on lower page) (http://www.astrosurf.org/lombry/menu-qsl.htm) 6/10/05
FM Antenna Gain and Pattern simulations (http://users.tns.net/~bb/) 6/7/05
Measured Gain for UHF antennas mounted outdoors & in (high loss) attic (http://www.avsforum.com/avs-vb/showthread.php?p=5410432#post5410432) 6/7/05
Excel spreadsheet comparing manufacturer's Gain, Front/Back Ratio & Beamwidth (http://hdtv.forsandiego.com/messages/1/2840.html?1109029581) 6/7/05
measured Gain and VSWR for popular indoor & outdoor UHF antennas (https://secure.connect.pbs.org/conferences/technology/2005/Sessions/TC05_43.htm) 6/7/05
measured Gain and VSWR for popular indoor & outdoor UHF antennas (.xls file) (http://hdtv.forsandiego.com/messages/1/3476.html?1118216319) 6/8/05
Antenna VSWR Degradation to DTV Receiver Sensitivity (http://www.avsforum.com/avs-vb/showthread.php?p=5399965#post5399965) 6/7/05
highest performing Indoor antenna - DB-2 from Antennasdirect (UHF only) (http://www.antennasdirect.com/HDTV_antenna_review.html)
Antenna performance chart (http://www.fmtunerinfo.com/antennas.html)
Antenna performance page (http://users.tns.net/~bb/index.html)
Antenna wiring, receiver/transmission noise
Antenna basics - excellent source for technical antenna & accessories info (http://www.hdtvprimer.com/ANTENNAS/basics.html) 7/28/05
Diagram of a Half-Wave Coaxial Balun & a handy calculator (http://n-lemma.com/calcs/dipole/balun.htm) 6/28/05
On-air DTV test with various length Coax Baluns (http://www.atechfabrication.com/tests/01-19-02_jbx21cd_tests.htm) 7/28/05
Entry point to purchase custom made Coax Baluns ($40) (http://www.atechfabrication.com/reception_solutions.htm) 7/28/05
Winegard transformers (http://www.winegard.com/offair/separatorsjoiners_print.htm) 7/28/05
Half-Wave Balun compared to wider bandwidth, low loss, Log Periodic Balun (http://palgong.kyungpook.ac.kr/~ysyoon/Pdf/weif_03.pdf) 7/28/05
Some basic Ferrite Balun design information (http://www.catchnet.com.au/~rjandusimports/tut_11b.html) 7/28/05
Maximixe performance of reception antenna installation (http://www.avsforum.com/avs-vb/showthread.php?p=5946459#post5946459) 7/28/05
Feeder radiation - installing a 1/2 wave coaxial transformer or choke balun (http://www.moonraker.com.au/techni/feeders.htm) 6/27/05
Baluns & Centre Connectors (Balanced/dipole antenna to Unbalanced Circuits) (http://www.cqcqcq.com/baluns.html) 6/28/05
Other antenna sites
DX FM site (http://www.dxfm.com/)
Channel Master reference chart (http://www.solidsignal.com/channelmaster_antenna_chart.asp)
Stacked Blake Aerials for Digital Television (http://www.bobmerritt.com/dtv/dtv.htm)
Televes Dat75 (http://www.televes.com/ingles/producto/ficha.asp?COD=242)
Maxus Super UHF Corner Reflector Yagi MXU59 - yagi deep fringe (http://www.warrenelectronics.com/antennas/mxu59.htm)
Great antenna selection (European models included...) (http://cpc.farnell.com/jsp/endecaSearch/searchPage2.jsp?N=1000110++411&=Audio&=0&N=0&OrgTT=&=&=true&No=0&Ntt=&Ntk=&comSearch=true)
Stacking TV antennas (http://pages.cthome.net/fmdx/stackant.html)
A 16-Bay (bowtie) UHF Ant - 2 ChannelMasters or Winegards... (http://www.hdtvprimer.com/ANTENNAS/16bay.html)
Vertical stacked yagis - Coyote Ranch (http://coyotecreekranch.com/DTV/)
Moonbounce (EME) UHF TVDX (http://internal.physics.uwa.edu.au/~agm/eme.html)
Yagi DX antenna arrays (http://community-2.webtv.net/GregBarker/NewTowerAntennas/)
Extra long yagis (http://www.wimo.de/cgi-bin/verteiler.pl?url=yagwimoshf_e.htm)
Amplifiers, preamplifiers & DTV info
Digital TV Signal Distortion & Interference (http://www.tvtechnology.com/features/digital_tv/f_digital_tv.shtml) 9/10/05
High Dynamic Range Receiver Parameters (http://www.wj.com/pdf/technotes/HighDynRangeRec.pdf) 9/10/05
- RF, RFIC & Microwave Theory, Design (http://www.odyseus.nildram.co.uk/Systems_And_Devices_Files/Linearity.pdf) RF... amplifier design & theory 9/10/05
Choosing the right antenna preamplifier (http://www.tvantenna.com/support/tutorials/uhf.html)
Special Frequency GaAsFET Preamplifiers (http://www.advancedreceiver.com/page12.html)
Angle Linear - pricing & ordering information (http://www.anglelinear.com/pricing/prices.html)
Johansson UHF preamplifiers (http://www.johansson.be/htmen/searchprod.php)
Johansson UHF preamplifiers (http://www.johansson.be/htmen/preamplifiers.php?ref=7103)
Build An E-pHEMT Low-Noise Amplifier (http://www.mwrf.com/Articles/Index.cfm?Ad=1&ArticleID=7763)
Micrin 3-channel E-pHMET preamplifier (http://www.micrin.com/pdf/LNA-AppNote.pdf)
STB's - Over The Air DTV/HDTV/Cable HDTV In The Clear - QAM (http://www.avsforum.com/avs-vb/showthread.php?s=&threadid=179095)
8-VSB, COFDM & DVB-T... (http://www.jivetv.com/ftopic1019-0.html&sid=81076f52b208c9ba068386e57ee328f7)
WHAT EXACTLY IS 8-VSB ANYWAY? (suitable OTA MPEG-II encoding and 8-VSB modulation) (http://www.broadcast.net/~sbe1/8vsb/8vsb.htm)
Earth's shape & latitude/longitude corrdinates
Earth's gravity definition - the Geoid (http://www.csr.utexas.edu/grace/gravity/gravity_definition.html) 6/9/05
Mean Sea Level, GPS, and the Geoid (http://www.esri.com/news/arcuser/0703/geoid1of3.html) 6/9/05
The Ellipsoid! Or is it the Spheroid? How About Geoid? (http://www.mentorsoftwareinc.com/CC/gistips/TIPS0998.HTM) 6/9/05
Mathworld - Equation 22, finding earth radius @ latitude (for oblate ellipsoid) (http://mathworld.wolfram.com/Ellipse.html) 6/9/05
The NGS GEOID Page - +/- adjustments for earth's oblate ellipse (http://www.ngs.noaa.gov/GEOID/) 6/9/05
NSG COMPUTATION OF USGG2003 GRAVIMETRIC GEOID HEIGHT (http://www.ngs.noaa.gov/cgi-bin/GEOID_STUFF/usgg2003_prompt1.prl) 6/9/05
NSG COMPUTATION OF GEOID03 GEOID HEIGHT (http://www.ngs.noaa.gov/cgi-bin/GEOID_STUFF/geoid03_prompt1.prl) 6/9/05
Earth - ellipse demo (http://www.ualberta.ca/~norris/navigation/EllipseDemo.html) 6/9/05
The Earth's Geoid (http://solid_earth.ou.edu/notes/geoid/earths_geoid.htm) 6/9/05
Earth - parametric latitude, WSG84 spheroid specs... (http://williams.best.vwh.net/ellipsoid/node1.html) 6/9/05
The Earth as an Ellipsoid, flattening, Datum history... (http://exchange.manifold.net/manifold/manuals/5_userman/mfd50The_Earth_as_an_Ellipsoid.htm) 6/9/05

Recommended from fellow AVS Members, other web sites & DX sites (who use enhanced tropospheric propagation to receive signals up to & over 1,000 miles distant). I try to keep separated different antenna types & categories for different uses/needs... Any other models to recommend or those listed to comment on?

Special thanks to AVS Member holl_ands, Wendell R. Breland & videobruce for additions & updates.

Well I saw Antennas Direct banner ad here, led me to add a few more excellent antennas...

Kudos for the very comprehensive antenna reference list.

You might want to add the following to the list:

The www.hdtvprimer.com website isn't logically laid out.
The fol. link should be added to ensure access to additional important links within the site:
http://www.hdtvprimer.com/ISSUES/erecting_antenna.html

FM Antenna Gain and Pattern simulations: http://users.tns.net/~bb/

Bob Chase (Houston Broadcast Engineer) compares measured Gain for numerous
UHF antennas mounted both outdoors and in his (high loss) attic:
http://www.avsforum.com/avs-vb/showthread.php?p=5410432#post5410432

I posted an Excel spreadsheet comparing the manufacturer's Gain, Front/Back Ratio and Beamwidth for a couple dozen UHF Antennas and provided comparison to the hdtvprimer NEC Simulation data for several selected antennas:
http://hdtv.forsandiego.com/messages/1/2840.html?1109029581

Kerry Kozad (Dielectric) finally posted his paper comparing the measured Gain and VSWR for several of the most popular indoor and outdoor UHF antennas, including a comparison to NEC Simulation results:
https://secure.connect.pbs.org/conferences/technology/2005/Sessions/TC05_43.htm

This is the most comprehensive VSWR measurements effort that I have seen to date,
filling in data for an area the antenna manufacturers woud rather not talk about.
VSWR is important for DTV when an antenna mounted preamp is not used due to
Noise Figure degradation (actually degradation of the DTV signal vectors) as the
signal bounces back and forth on the long downlead.
More on this subject can be found in my fol. post:
http://www.avsforum.com/avs-vb/showthread.php?p=5399965#post5399965

Thanks holl_ands! :) Added & dated those links & gave you credit. Guess I have some more reading to do. Many of these solutions may hopefully be more permanent for the future, unlike a lot of upgrades in the A/V world...

The VHF-UHF ANTENNAS COMPARED FOR OUTDOOR USE is the same as the HEAVY METAL PT1 link, except the latter link has the pretty pictures removed.

HEAVY METAL PT2 (actually lightweight indoor antennas) is at fol link:
http://www.hdtvexpert.com/pages/antin.htm

Thanks again holl_ands! :) I'll try to get these links @ bottom more in a relative grouping to keep them better organized...

FYI: Kerry Cozad's Gain Summary charts were way too small to read.
See latest update to fol post for Excel Spreadsheets extracted from his presentation,
which are much easier to see now:
http://hdtv.forsandiego.com/messages/1/3476.html?1118216319

Thanks again holl_ands & again for the compliment. :) Noted the .xls file link just below the 1st one.

I was also looking at getting my street elevations, etc... correct through topographic maps. Worked so well after printing from the 1st link I feel indebted to order their $15 custom laminated map.

Here's the topo map links added for now:

Custom topographic maps - free preview (http://www.mytopo.com/index.cfm)
Digital Topo Maps (http://www.digital-topo-maps.com/)
USGS Maps (http://www.usgs.gov/)
TopoZone (http://www.topozone.com/default.asp)

Wasn't surfing long, so there must be other good ones. 1st link worked just fine for me. ;)

The motherload of topo and other maps.
Hi-rez viewing requires subscription. You can also order hi-rez prints for a price.
SEARCH by LAT/LONG, Address, City, Zipcode, etc will reveal over a dozen different
topographic products, including satellite and aerial images:
http://www.terraserver.com/

Punch in street address and GeoCode's Eagle will show your GPS LAT/LONG on a Topo Map:
http://www.geocode.com/modules.php?name=TestDrive_Eagle

Tailor coordinates to yield Topo or Aerial Photo Map in jpg format:
http://www.lostoutdoors.com/newmap.html

I use the free RADIO MOBILE Propagation Prediction Program to view not only very high
resolution topographic maps, but can also use the "MERGE PICTURE" function to display
various images automatically downloaded onto the topo map. This includes road maps
from MAPPOINT/MAPQUEST, LANDSAT IR images, TerraServer images, and Tiger data.
The Topo map data can be either automatically downloaded when you need it, or you
can manually download the much higher resolution (30 m) SRTM-1 database.
See my 22Mar post in the fol thread for RM links and examples:
http://hdtv.forsandiego.com/messages/1/2846.html?1112095186

OH, almost forgot...RM also calculates propagation characteristics over irregular terrain.
So you can investigate how much antenna/preamp gain you need.
And did I say that it was FREE???

Satellite Pointing Angle for different satellites:
http://www.nerosoft.com/SatCalcView.asp

Thanks again holl_ands - cool link! :) I did a spreadsheet calc but can't upload the .xls (Excel) or .sxc (OpenOffice) to my FTP Tripod site right now (AceFTP seems stubborn right now). Funny other same types are there, I must be rusty. Anyway the calcs I have need just 3 parameters (1st 3 numbers):

Antenna tilt angle
Distance to tower (miles) 8.65 45,672.00 (feet)
Height of transmission (from Sea Level) 410.00
Height of antenna (from Sea Level) 1,245.00
Height difference antenna-transmission tower 835.00
Gross tilt angle to point antenna (degrees) 91.05

Earth circumference equator (miles) 24,902.00
Earth circumference poles (miles) 24,860.00
Mean earth diameter (miles) 7,926.55
Mean earth radius (miles) 3,963.28
Net height formed w/earth curvature (miles) .009 49.84 (feet)
Net tilt angle to point antenna (from Theta, 90 degrees level) 91.11

To find the tilt angle if needed to point antenna “directly” at tower you can use equation: TAN(a/b)*(180/PI())

a=transmission tower height (Mean Sea Level) minus antenna height (Mean Sea Level)
b=distance to tower from antenna

Just make sure feet, miles, meters... are same units in equations. To adjust antenna heights/tilts angles for earth's curvature, I used a spherical cap formula to find the “extra height” added relative to reception antenna. This was based on the earth's average radius (3,956.55 miles) assuming it was spherical constant. The diameter of the equator actually exceeds the diameter of poles by about 1/300, but an averaged radius still seems to get within 10th of a degree or so of tilt angle accuracy (about as close as using K Factor of 1.333):

Antenna height gained by earths curvature: 3,956.55-SQRT(3,956.55^2-tower distance miles^2)


***************
The equator is 3,963.19059 miles radius & the poles 3,949.90276... To get a very accurate “direct point at the tower angle w/earth's curvature” use an oblate ellipsoid of rotation & calculate the angle on a triangle of 3 known sides.

NOTE: 1st obtain & convert Geodetic/Geodesic to Geocentric Latitudes (http://www.mathworks.com/access/helpdesk/help/toolbox/aeroblks/geodetictogeocentriclatitude.html#1397439) (equation below). Unless you're @ the equator, a Geocentric or “flattened” latitude will usually be less than given on a map or site unless stated otherwise. Longitude naturally stays the same value (is unaffected by flattening).

New Geocentric latitude(s) in radians: =ATAN((1-(1/298.257223563))*TAN(geodetic or geodesic latitude))

From 2 Geocentric latitudes each radius can be found by using a & b as semi-major & minor axes (earth radius @ point) using Mathworld - Ellipse equation 22 (http://mathworld.wolfram.com/Ellipse.html):

=SQRT((3,963.19059^2*3,949.90276^2)/(3,963.19059^2*COS(latitude)^2+3,949.90276^2*SIN(latitude)^2 ))

Each latitude location gets it's own radius (2 total). To complete the radius length of each, add the total heights of respective antenna-tower above Mean Sea Level. You can adjust the final radius results with the NSG COMPUTATION OF USGG2003 GRAVIMETRIC GEOID HEGHT (http://www.ngs.noaa.gov/cgi-bin/GEOID_STUFF/usgg2003_prompt1.prl) or NSG COMPUTATION OF GEOID03 GEOID HEIGHT (http://www.ngs.noaa.gov/cgi-bin/GEOID_STUFF/geoid03_prompt1.prl). The last adjustment is usually in only the tens of meters for the Geoid height over/under the “smooth mathematical” earth ellipsoid...

The 3rd triangle side is the tower-antenna distance. This is derived from the Geocentric latitude/longitude angles & both radii from earth center. No need to find out distances in miles or km, just accurate latitudes/longitudes. This calculates the chord or straight-line distance of 2 points on an ellipsoid. The distance is:

=SQRT((radius1^2+radius2^2)-2*radius1*radius2*(COS(lat1)*COS(lat2)+COS(long1-long2)*SIN(lat1)*SIN(lat2)))

* NOTE: this equation above uses 90 degrees MINUS latitude for lat1 & lat2 for north hemisphere! This is because equation uses Phi/Latitude angle from 0 to 180 degrees starting from “North Pole” not equator, for south hemisphere it's 90 degrees plus latitude. This is how Phi is actually referenced in polar, spherical... coordinates.

Now with final triangle lengths a,b,c, just use the Law of Cosines to find either or both angles from tower or antenna: ACOS angle =((b^2+c^2-a^2)/(2*b*c)) *(180/pi()) “a” will always be the side opposite the angle you want (in degrees).

Answer also checks out if you use x,y,z Cartesian values converted from polar coordinates by length= SQRT((x1-x2)^2+(y1-y2)^2+(z1-z2)^2). Things are a lot easier when you have radians & radius equal to 1. ;)
***************


These last adjustments seem to show the 1st result is just a “hair off”, more so seemingly when tower distances get closer (maybe because it's a spherical cap formula that's distorted slightly, I was looking to adjust to an elliptical cap & other factors got more complex). Since both adjustments are in my spreadsheet (I should get to post) any future calcs won't take much time at all...

So, some interesting related links:

Earth's gravity definition - the Geoid (http://www.csr.utexas.edu/grace/gravity/gravity_definition.html) 6/9/05
Mean Sea Level, GPS, and the Geoid (http://www.esri.com/news/arcuser/0703/geoid1of3.html) 6/9/05
The Ellipsoid! Or is it the Spheroid? How About Geoid? (http://www.mentorsoftwareinc.com/CC/gistips/TIPS0998.HTM) 6/9/05
Mathworld - Equation 22, finding earth radius @ latitude (for oblate ellipsoid) (http://mathworld.wolfram.com/Ellipse.html) 6/9/05
The NGS GEOID Page - +/- adjustments for earth's oblate ellipse (http://www.ngs.noaa.gov/GEOID/) 6/9/05
NSG COMPUTATION OF USGG2003 GRAVIMETRIC GEOID HEIGHT (http://www.ngs.noaa.gov/cgi-bin/GEOID_STUFF/usgg2003_prompt1.prl) 6/9/05
NSG COMPUTATION OF GEOID03 GEOID HEIGHT (http://www.ngs.noaa.gov/cgi-bin/GEOID_STUFF/geoid03_prompt1.prl) 6/9/05
Earth - ellipse demo (http://www.ualberta.ca/~norris/navigation/EllipseDemo.html) 6/9/05
The Earth's Geoid (http://solid_earth.ou.edu/notes/geoid/earths_geoid.htm) 6/9/05
Earth - parametric latitude, WSG84 spheroid specs... (http://williams.best.vwh.net/ellipsoid/node1.html) 6/9/05
The Earth as an Ellipsoid, flattening Datum history... (http://exchange.manifold.net/manifold/manuals/5_userman/mfd50The_Earth_as_an_Ellipsoid.htm) 6/9/05

Current worldwide list of Radio & TV Stations, with channel, power, height, lat/long info.
Click on station call letters for map with station location.
http://www.w9wi.com
Not as easy or as quick as www.2150.com/broadcast/default.asp

Yet another list of DTV Stations includes proposed assignment change list:
http://www.tvtower.com/hdtv_status.html

I find the following to be the most comprehensive list of Analog and DTV stations
in Southern California, since it combines all the stations in a particular region into
a single list, eg. LA/Indio/PalmSprings or SD/Baha:
http://www.tvradioworld.com/region1/ca/

National and Worldwide lists of Broadcast Radio, TV and Ham radio stations:
http://www.tvradioworld.com/default.asp

Very useful site, including Doug Lung's weekly RF REPORT column re DTV Technology:
http://www.tvtechnology.com/

Again, thanks holl_ands! :D Just put all those other links in, for now just have some hyperlinks to fill out under Accessories...

A tip of the AVS hat to RayL Jr. & holl_ands, for a great topic.

Thanks Ken! :) Regarding that Antenna Tilt Angle page I had K Factor set @ Infinity. With the default K Factor of 1.33 I got .079 degrees "up" @ 8.5 miles & .025 degrees "down" @ 50 miles. That's within about 1/10th degree of real earth curvature "straight point" adjustment...

K Factor takes into account the effect of the refraction on RF propagation, & varies with climate & location.

I also found these 2 links:

Antenna Up/Down Tilt Calculator (compensates for Earth curvature) (http://www.ecommwireless.com/cgi-local/tilt.main.cgi)
Antenna - K-Factor & climate effects (http://www.tvtechnology.com/features/On-RF/f-DL-signals.shtml)

A tip of the AVS hat to RayL Jr. & holl_ands, for a great topic.Just noticed it's a sticky after posting... Thanks again Ken H, holl_ands & AVS! :cool: :cool: :cool: :D :D :D

Cool topic, lots for me to check out before I try some ATSC DXing...

Considering the beamwidth of even high-gain UHF antennas, are you really getting better results by adding "tilt" to terrestrial antenna installations? Seeing the 'less than one degree' remarks above makes me think it is not truly going to accomplish much. (In ham radio, we only use tilt rotation for satellite contacts.)

Actually my friend in Buffalo commented "What if an office building is in the way?". Guess it's more acedemic at this point & testing for actual signal strength by rotate & tilt, height, location, obstructions, space... (whether mechanically or physically) is the most accurate way.

Nice to know these calcs can get very precise. BTW, I changed my last equation from spherical cap derivation to finding r1 & r2 radius of earth ellipse (antenna-tower latitudes in radians). Along w/distance to tower it makes a triangle with which I just use the Law of Cosines (knowing 3 sides): CosA=(b^2+c^2-a^2)/(2*b*c). This is direct point but doesn't use K Factor. You can find angles from both transmitter & antenna...

Well, I played with ellipses & geodesics a lot with speakers/enclosures, domes... & was familiar with the terminology of GPS coordinate conversion, so I dug up some more useful links. Here's the links:

Vincenty formula for distance between two Latitude/Longitude points (http://www.movable-type.co.uk/scripts/LatLongVincenty.html) 6/12/05
Vincenty's Formulae, Inverse Method (http://www.ga.gov.au/nmd/geodesy/datums/vincenty_inverse.jsp) 6/14/05
Forward Inverse - Azimuth, distance... ellipsoidal calc program (http://www.mentorsoftwareinc.com/PRODUCTS/FWDINV.HTM) 6/14/05
Ellipsoid Radii Calculator (http://www.mentorsoftwareinc.com/FREEBIE/FREE0999.HTM) 6/14/05
Vincenty Ellipsoid corrected “Great Circle Calculator” (http://williams.best.vwh.net/gccalc.htm) 6/14/05
Distance and bearig between two Latitude/Longitude points (http://www.movable-type.co.uk/scripts/LatLong.html) 6/14/05
Freeware DOS program calculates ellipsoidal geodesic path (http://home.earthlink.net/~rcmcc/) 6/14/05

Slight correction on accurate calcs (edited calc post above) - when you enter say a WGS84 Geodetic lat/long it has to be converted to Geocentric angles on ellipse in math calcs 1st (at the latitude/height correction). Geodetic, geodesic, geographic... references latitudes on a sphere or "Geoid". The Geoid coordinates are an accurate reference for both terrestrial & relative astronomical calcs (also use Geocentric). :)

Any other models to recommend or those listed to comment on?

Ray, Very nice work.

I would like to point out the Winegard PR-9032 (http://www.hdtvprimer.com/ANTENNAS/comparing.html) is a top performing UHF antenna and can be purchased for a lot less than the imports.

For the DIY's: If you have low signal levels in your area then construct yourself a 1/2 wave coaxial balun for the very last dB in signal level.

Thanks for the info & compliment Wendell! :) Good suggestion, balanced connections also help in pro audio installs (high power, long multiple runs..), also info from Rane on how balanced/unbalanced works w/transformers. Here's 1 antenna link:

Feeder radiation - installing a 1/2 wave coaxial transformer or choke balun (http://www.moonraker.com.au/techni/feeders.htm)

Thanks again Wendell. :) I'm not too familiar with antenna baluns, but pretty much understand the "electronics"...

I also read from this link on transformer & coax baluns (http://lists.contesting.com/pipermail/towertalk/2002-December/053618.html) (bottom 1/3 page) the coax balun is more frequency specific & transformer balun is broadband. This transformer balun link Baluns & Centre Connectors (Balanced/dipole antenna to Unbalanced Circuits) (http://www.cqcqcq.com/baluns.html) seemed to help me see it better...

So I'd assume the coax is a nice cheap way for pulling in lower/difficult channels or a specific "boost" (or noise attenuation) to 1 channel?

So I'd assume the coax is a nice cheap way for pulling in lower/difficult channels or a specific "boost" (or noise attenuation) to 1 channel?

Ray,

I took a lot of liberty when reference was made to a coaxial balun. It was assumed a DIY would be a technical person.

As to the 1/2λ Coaxial Balun being narrowband, that is correct for the context the author is referring to (Amateur Radio 80 to 10 meter band [~3 to 30 MHz] or ~3.3 octaves). UHF TV channel 14 to 59 is 470 to 740 MHz, that is less than 1 octave. I did a simulation of a 1/2λ coaxial balun in Electronic Workbench and the Bode Plot showed 0 dB of loss at the design channel of 52 (700 MHz), -1.76 dB at channel 14, and -0.05 dB at channel 59. The very best broadband baluns (ferrite core) have an insertion loss of 1.25 to 1.5 dB.

For me: In my area the most desired OTA digital channel is 52, the local CBS affiliate. They have a figure 8 pattern and not much EPR. I am in the null of the pattern and about 20 miles away. I tried to use my old and trusty Channel Master 4 bay bow tie (3021) but could not get reliable reception. Next I tried a Channel Master 4248 and it was no better.

Then I procured a Winegard PR-9032, constructed a 1/2λ coaxial balun and installed. It received channel 52 very well (59 to 65% on MIT MDP-120's). I then installed a Winegard AP-4700 pre amp so that I could install several signal splitters. This has been working very well for 1-1/2 years.

At the time all of this was done I was still employed and had the luxury of a Tektronix RFM151 (http://www.tek.com/Measurement/cgi-bin/framed.pl?Document=/Measurement/App_Notes/rfm151-rpi/&FrameSet=communications) TV channel signal level meter and analyzer and a Hewlett-Packard spectrum analyzer to test with.

73's
WA5RMP

What would be the loss for a coaxial balun best cut to cover the entire UHF band?
Do your simulation results assume a particular antenna....or a perfect 300 ohm source?

FYI: Most 4:1 Coaxial Balun discussions are for Ham radio applications trying to match
a 50 ohm transmitter to a nominal 200 ohm impedance antenna.
A 4:1 Coaxial Balun of the correct length can also be used to match a nominal 300 ohm
UHF antenna to a 75 ohm preamp or downlead cable.

See fol. for a diagram of a Half-Wave Coaxial Balun and a handy Calculator:
http://n-lemma.com/calcs/dipole/balun.htm
Note the default velocity factor (0.66) is for solid polyethelene insulator found in RG-6.

See fol. for on-air DTV test with various length Coax Baluns:
http://www.atechfabrication.com/tests/01-19-02_jbx21cd_tests.htm
and entry point to purchase custom made Coax Baluns ($40):
http://www.atechfabrication.com/reception_solutions.htm

Also see fol. Half-Wave Balun compared to wider bandwidth, low loss, Log Periodic Balun:
http://palgong.kyungpook.ac.kr/~ysyoon/Pdf/weif_03.pdf

I have an extra D*** Network dish installed on my roof top. Can I use this dish to get HDTV local signals?? Any specific thread on this questions on AVSFORUM?? I am waiting for Sammy 6168 and planning to watch local HDTV through its built in tuner??

Basically, the "nice" baluns, meaning the ones that are typically 3/4" in diameter, are probably all dual wind transformers and lose in the neighborhood of 1/2dB. The smaller, cheaper baluns, often called "indoor" and about 1/2" in diameter, are single-wind autoformers whose performance varies wildly over the UHF band. A few years ago, a physics professor who was briefly a member here tested one of those autoformers and found that its impedance over the UHF band varied from about 1dB to about 7dB.

I'm pretty sure that the Radio Shack balun made for connecting a 300 ohm twin-lead via screw terminals, to a rear chassis 75 ohm input is a reasonably well engineered balun, but its "F" connection is a push connector, so it may be impractical to make is mechanically reliable and weatherproof if used outdoors.

I'm not sure about smaller parabolic dishes used as an antenna & receiving VHF/UHF OTA HDTV. Mounting higher is most always better in this case. Channel Master had a 7' dish that outperformed just about anything that could fit in someones yard/roof, but wind loads become more of a concern w/the bigger dishes.

Parabolic collectors are very effective at focusing the energy source. I've designed 10”-8' parabolic solar collectors back in the mid-late 70's to run a Sterling hi-temp steam engine approaching 30% total efficiency (available PV cells are about 5-20%). Lots of web resources on that. I imagined they could be a small cheap source for homemade power in every home. Then Ted Tuner coincidentally grabbed up all the nice surplus parabolic “frames” & started CNN...

I assume that the 3/4" baluns that I have experimented with in various field applications are dual wind transformers because I have successfully used them to eliminate ground loops, whereas I have always been unsuccessful at eliminating ground loops with the cheaper, 1/2" diameter baluns. I assume, based on that, that the 1/2" baluns are single wind autoformers in which there is a tap connection point such that three-fourths of the windings are on one side of it and one side are on the other side. I have not cut a whole lot of them open.

When you use the term ferrite baluns, are you limiting that to single-wind autoformers with ferrite cores, or might that term also be used to describe devices with dual isolated windings that might also have ferrite cores? I'm certain that the frequency response of the latter will be much flatter than the frequency loss of the former.

Right now, my only spectrum analyzer that has fine enough vertical resolution to meaningfully evaluate fractional dB variations is my disassembled AVCOM (started to fix the battery charger, but never got around to finishing the job) then only way that I could endeavor to test what I have lying around would be to maybe couple four of them together and divide the measured losses by four.

In light of the fact that your calculator had determined that a so-called "coaxial balun" optimized to the UHF band would have insertion losses of -0.69dB at 470 MHz, 0.0dB at 605 MHz (Mid Band) and -0.51dB at 740MHz., I don't see why you would be surprised to hear that someone who had once measured what were believed to be dual wind transformer baluns had losses consistent with the coaxial balun that you have simulated.

I just cut the fork lugs off two Channel Master 7982 Matching transformers, those being of the indoor, narrow body design that I often derisively refer to as the "cheap ones", twisted the leads together, and measured the signal strengths of eleven cable TV channels, 6 VHF and 5 Hyperband or higher, to measure their insertion loss, using a Leader LF 941 FSM, which regrettably, only has a resolution of 1dB. I then divided the difference by two.

4 (67Mz) no insertion loss
5 (77Mz) 1/2 dB per balun
7 (175Mz) 1dB
9 (187Mz) 1/2dB
11 (199Mz) 1dB
13 (211Mz) 1dB

65 (469Mz) 1/2 dB
75 (529Mz) 1 dB
85 (589Mz) 1dB
110 (709Mz) 1/2dB
120 (769Mz) 1dB

Amazing. I had tested a handful of baluns about ten years ago, when I first moved to the Washington, DC market and began servicing master antenna systems, as some buildings distributed local broadcast channels 20 (507Mz) and 26 (543Mz) on their natural frequencies, so I needed to have some idea of what the hardware I was using was capable of doing at those frequencies. As I have remarked in other threads, I had observed erratic, inconsistent insertion loss performance with the narrow diameter, so-called "indoor" baluns at different frequencies, which also have consistently failed me as ground loop isolators, but I never have had any reason to attempt to replicate the testing that I did.

I'm still inclined to doubt that these Channel Master $.42 baluns, are fairly evenly losing just .7dB on the average in both bands. My test cable signal goes through a two-way hybrid, then a -9dB directional coupler, and the tap port splits again with one leg going to my viewing TV and the other available to my test bench, so it is possible that this double balun somehow stabilizes the load impedance better than does my Leader meter by itself, but that, like so many things in antenna development, is just speculation.

A lot of time is spent at this forum with people speculating on how they MIGHT improve their S/N ratios by a fraction of a dB, but such theoretical improvements so small can easily be offset by other unintended effects. For example, when Mr. Breland calculated the expected losses for his 605Mz coaxial balun, which he reported to the nearest one-hundredth of a dB, he was assuming a perfect 300 ohm source, but the coaxial balun will be used to enable the nominally 300 ohm source to drive a 75 ohm load, which will enjoy less than optimal power transfer efficiency. The inefficiency of driving a 75 ohm load with a 300 ohm source could result in more signal reduction than is gained by minimizing the insertion loss. Maybe it is better to use a preamp with a natural 300 ohm input instead.

I am fortunate in that I do most of my work on high-rise buildings within ten miles of most of the transmitters, so my broadcast DVT antennas naturally develop S/N ratios of 40 to 60dB or more. But those of you who feel a need to scrounge for fractional increases to your own signal levels are commonly 40 miles or more from the transmitters, meaning that your signal goes through some vegetation, and just the rustling of distant leaves will make it go up and down by a few dB even on a clear day. If you have an unreliable signal lock, such that you occasionally experience pixelating or blocking or freezing, the likelihood that a fractional increase in your S/N ratio will notably improve the reliability of your reception link from unacceptable to acceptable is near zilch.

If you want to spend time and money improving your signal reliability, spend it on the antenna, the mast, the preamplifier or the aiming.

Ray, I apologize that your reference thread has been hijacked.

In this thread I have stated clearly and concisely what materials and equipment were used in reference to UHF ATSC television reception. Mr. Breland has made no assumptions. I asserted that name brand ferrite baluns would have an insertion loss of ~ 1 to 1.5 dB in the UHF band. Links were provided to substantiate this statement. The Tektronix RFM151 has 10 times the resolution of the Leader LF 941 therefore I will not even comment on the values posted above except to say they are meaningless. In addition, the LF 941 is not suitable for DTV channel measurements, the LF 941D should be used. A 1/2λ coaxial balun does not have insertion loss in the design range.

A variant of a resistive 300Ω source: If the source (folded dipole for 9032 and 4248) should be 272Ω j, +127Ω i at the frequency of interest there will be a reduction in signal level of -0.229 dB using a 1/2λ coaxial balun. Under the same conditions a ferrite style balun with an insertion loss of 1.250 dB will have a total signal reduction of -1.556 dB (1.250 + 0.306).


For those that have problems with hum: I have used with success the MCM 33-8700 (http://www.mcmelectronics.com/product/33-8700) Ground Insolation Transformer for several years. If you place an order, use Source Code 53108, then click Update. Should be lower pricing.

For the DIY’s using 75Ω coax cable: Take two name brand 300Ω to 75Ω baluns, connect one 300Ω lead to the lead of a 150pF disc capacitor (I use disc caps with a 1KV DC rating). Connect the other lead of this disc capacitor to the second baluns 300Ω lead. Repeat these steps for the other 300Ω leads.

I have constructed these using a small aluminum box. The ferrite cores with their windings were removed from the original housing. The twin leads were discarded. The remaining components and the two disc caps were attached to a G10 perf board. A chassis mount F connector was installed at each end of the box. One of the F connectors must be mounted using fiber shoulder washers to isolate it from the box.


A recap: The Winegard Model PR-9032 in conjunction with a 1/2λ coaxial balun provides reliable reception of DTV Channel 52 in my area. Channel Master’s Model 4248 and Model 3021 (with Model 0089 Balun) did not provide reliable reception on this channel. Where DTV reception is concerned, a dB or so at the receiving antenna can mean the difference between reception and no reception.

FWIW: If one would like to analyze the data stream of a DTV signal check out TSReader (http://www.coolstf.com/tsreader/) . It can be used for OTA, Satellite and cable.

07-12-2005 Edited for clarification
07-13-2005 Attached a schematic of a 300Ω to 75Ω Ferrite Balun
11-23-2009 Update MCM link

I posted measurements for seven different baluns, incl. the CM3075 Outdoor 3/4" Diameter Balun as fol:
http://hdtv.forsandiego.com/messages/1/2489.html

The CM3075 (from www.outpost.com, i.e. Frys) was the best of the several Outdoor Baluns tested,
but didn't have quite as low a loss as the several cheap indoor baluns tested.

The two different R-S Outdoor Balun models were measured to have significantly higher loss.

Note that since I retired and no longer have ready access to a room full of test equipment,
a non-traditional measurement method was used (dBmV measurements via Cable STB) for back-to-back baluns.

Also note fol. link to another balun test, including a DIY coax balun description:
http://www.kyes.com/antenna/balun.html

Given that the vast majority of stations will end up after the digital transition on channels between 7 and 51, I was curious to know if there are antenna manufacturers making new antennas that are tuned specifically for these frequencies?

If I recall correctly, I once installed a Terk, "magic wand" shaped antenna for carltonrice under a rain gutter, which was better suited to function as a rain gutter.

The Winegard PR-9XXX antennas showed really ugly polar plots at the highest frequencies, so they are probably "tuned" as well as they will ever be for channels 14-51. The front-to-back ratio at high frequencies is horrible and its gain is about 4dB less at channel 69 than at channel 50. The polar plots on the HDTVPrimer site look more like what you'd get of you took about one tenth as many polar points and connected them with a French Curve. If they developed those plots with a primitive simulator, I wonder if it took into account the fact that the mast is in front of the dipole in that series of antenna, and has greater disruptive effect on the shorter wavelengths.

There are probably more people here who got better performance by switching from a PR-9032 to a CM4248 than vice versa, but what most of them don't realize is, the antenna that worked better for them was the one that had the more fortuitously located troughs between its side lobes.

By the way, eight of the eleven channels I measured the signal loss on were analogs. And for the other three, who cares if I am measuring peak or RMS? The loss will be the same.

Given that the vast majority of stations will end up after the digital transition on channels between 7 and 51, I was curious to know if there are antenna manufacturers making new antennas that are tuned specifically for these frequencies?

A channel 7 antenna only needs to be about 30 or so inches wide. Nearly all of the lowband transmitters in the largest metropolitan markets are giving up their lowband assignment. In my market, 2, 4, and 5 will be staying on UHF, whereas 7, 9, 11 and 13 will be moving down. I think you'll see a lot of 7-51 antennas. The booms will be nearly as long as they are now, but they will have much less wind load and will last a lot longer.

I just received a Research Communications 9250 UHF preamp with a specified gain of 20 dB and a noise figure of 0.4 db. As seen here: http://www.researchcomms.com/hdtv.html I have verified the gain here, but it is going to be a while before I connect it to an antenna. If anyone nearby (SE CT or RI) has away to test it let me know. John

I've tried several indoor antenas and so far have not found a better one than what I currently have - an old (6+ years at least) Recoton 350 non-amplified antenna. It has UHF and VHF reception that hands down beats the likes of Radio Shack's 1880 or RCA ANT200 (both amplified).

I now use the Recoton with my Panasonic TH-42PX50U and I get all digital channels in the DC area and a quite decent reception of most analog channels. In contrast, the RadioShack could only get some of the digital and was notably worse on most analog channels - and it worked OK only if the amp was off or close to max... Go figure...

I guess they don't make them like this anymore - if anyone knows a good indoor antenna for a metropolitan area, please post.

Thanks!

Does anyone have any experience with the sat dish style ant's like terk TV42 and TV44 that clip onto the dish?

I haven't tried an ant yet to see what kind of reception I get, but I'm guessing it should be pretty decent considering on a good weather day I have line of sight to the broadcast ant's on the Sears and Hancock 20 miles away.

Interesting concept. Looks like a big paper clip bent around the dish:

http://ai.pricegrabber.com/product_images/431000-431999/431476_125.jpg

Seems not as good as say a 2-bay indoor/outdoor antenna, but for stronger or line-of-sight reception areas. Otherwise most reviews (also on the TV50) seems to relegate them to "a piece of junk"... At least from some Terk reviews @ AudioReview (http://ecoustics.audioreview.com/cat/audioreview/accessories/others/terk/PRD_123443_1590crx.aspx).

If you really want/need a streamlined solution & have the bigger dish for the TV42, it might actually work pretty good in your case. If there's a return policy, maybe try it just before some bad weather hits.

Otherwise if you have room for an outdoor 2-bay, you can get a stronger signal or at least are more guaranteed to for about the same price.

Those among you willing to go to heroic lengths to maximixe the performance of your reception antenna installation may choose to visit HERE (http://www.avsforum.com/avs-vb/showthread.php?p=5946459#post5946459).

Thanks to a number of members for the links here mentioned the past few weeks, I'll add & sort these in:

Antenna basics - excellent source for technical antenna & accessories info (http://www.hdtvprimer.com/ANTENNAS/basics.html) 7/28/05
On-air DTV test with various length Coax Baluns (http://www.atechfabrication.com/tests/01-19-02_jbx21cd_tests.htm) 7/28/05
Entry point to purchase custom made Coax Baluns ($40) (http://www.atechfabrication.com/reception_solutions.htm) 7/28/05
Winegard transformers (http://www.winegard.com/offair/separatorsjoiners_print.htm) 7/28/05
Half-Wave Balun compared to wider bandwidth, low loss, Log Periodic Balun (http://palgong.kyungpook.ac.kr/~ysyoon/Pdf/weif_03.pdf) 7/28/05
Some basic Ferrite Balun design information (http://www.catchnet.com.au/~rjandusimports/tut_11b.html) 7/28/05
Maximixe performance of reception antenna installation (http://www.avsforum.com/avs-vb/showthread.php?p=5946459#post5946459) 7/28/05


If I were that concerned for higher UHF frequencies in my area, Europeans seem to like the Televes DAT-75 (http://www.hdtvprimer.com/ANTENNAS/DAT75.html). I guess to each his/her own area, situation & requirements. I've seen vicious but informative arguments w/the Channel Master 8-bay vs. Winegard & other yagis between what seems to be experienced pros/installers... in other threads/forums. When does one say they've looked @ say Comparing the common antenna types (http://www.hdtvprimer.com/ANTENNAS/comparing.html) long enough? ;)

AntAltMike's link is interesting on improving reception drawing a big ellipse & finding optimum location. I've designed sealed concrete cast ellipsoid speaker enclosures using Fibonacci cancellation with a lot of help from Cantrell's ellipse formulas in a spreadsheet, mitigating need for 1/2 wave resonance damping material which can also “muffle” sound. VERY precise & no Calc III needed. :)

Here is something that I would consider useful to see calculated. If you have an antenna with a 300 ohm dipole and, in a given field, it develops 10dBmV of signal power when its output terminals are impressed upon a 300 ohm load, which is what it "sees" when connected to a ferrite balun, then how much power would be developed if the output of that same 300 ohm source were instead impressed upon a 75 ohm load, which is what we appear to be doing when we use a 1/2 wave balun?

If it is less than when impressed upon a 300 ohm load, then that differential must be subtracted in the transmission link calculation just as the calculated or actual loss through the ferrite baluns is. In other words, hypothetically, if a ferrite balun 300 ohm input is the optimal load and if its insertion loss is 1.5dB, but if the use of a 1/2 wave balun results in the development of 1dB less of power because of the impedance mismatch, then the differential in power and therefore S/N present at the tuner is only 1/2 dB. I'd like to see the order of magnitude of the net power differential between the two different transmission links before I spend any time dealing with awkward 1/2 wave baluns.

Your experience with the PR-9032 over the Channel Master 4248 is just that: your experience. Two or three years ago, there were legions of members here who swore that the Channel Master yagi outperformed the Winegard. I told them that the difference couldn't amount to more than a warm pot of spit, and that I used and still use a lot more Winegard PRs than CMs, because they cost less and I have three Winegard stocking dealers within 30 miles of me. But I never outlasted the Channel Master afficianados

You should further contemplate Winegard's channel 69 plot, and notice that it is asymmetrical, which is consistent with my speculation that the mast causes it, because the mast is off to the side of the boom, and should also consider that the effects of a larger mast could well disrupt channels in the 50s. In attic applications, with no internal onstructins and no mast, the plots would look more like they do in the HDTVPrimer site, and I imagine that a plastic mast extension might make the mast disruption negligible as well.

But don't lose sight of what I said in the post in which I criticized the PR series upper UHF performance. I said it wouldn't likely be redesigned because it already seems to do well up to 700 Mz, which is where the band will end when the transition is over.

(Edited to extinguish flame war)

In response to Post Number 49

A dipole antenna has the electrical equivalent of a series connected Resistance, Capacitance and Inductance. Z = 272+j127Ω is the rectangular values of the polar form of Z = 300∠25°Ω. √(272² + 127²) = 300, Θ = ATAN(127/272) and is = to 25°. The plus value for j means it is inductive (if j were negative, then it would be capacitive). Absolutely nothing vague about it!!!!!

And once again the common 300Ω to 75Ω commercial ferrite balun is a Z of 4:1 or E of 2:1. For an IDEAL balun. If 1V is applied to the 300Ω terminals from a 300Ω source then there will be 0.5V (a drop of 6dB) across the 75Ω terminal when terminated with 75Ω. The source power and the terminated power levels are the same (IDEAL), P = E²/Z. The 4:1, 1/2λ coaxial balun operates the same way, 300Ω to 75Ω. THE DIFFERENCE: a 1/2λ coaxial balun does not have any core IR losses.

The PR-9032 (as most TV antennas and transmissions in the US) is horizontally polarized. Since the E Field is in the H Plane the vertical mast should have little effect on the reception. Most TV antennas I have installed used this form for mechanical mounting.

A search was made for PR-9032 for all AVS Forums, 12 threads were returned. There was only one post that had a negative comment. I know of a few that connected their balun leads to the 300Ω pass thru terminals and posted here their new Channel Master 4248 was no good. I suspect some have done the same with their PR-9032.


In response to Post Number 47

There are only 16 DTV stations in the CONUS that is above Channel 59. There is no channel 66 or 68 on the east coast. Channel 61 is WNET (PBS).


Conclusion:

In certain situations a coaxial balun will help with difficult ATSC channel reception. In most cases it probably will not make any difference in reception. The Winegard PR-9032 is one of the top performing UHF antennas.

To solve for Z and Θ requires only HS level math. A technical person should have answered these questions without any problem. There are no “single-wind autoformers” baluns, see the schematic I posted. I can only conclude that you are not a technical person and you need to stop trying to pose as one.

07-31-2005 Edited to insert spaces
08-16-2005 Edited to correct notations

OK folks a little background on me. I was a Technical Services Supervisor for 34 years for the statewide public broadcasting system. I have retired and have no ties or connections to any type organization, I do own a small home business. As of June 2007 we have purchased common shares of stock in Dolby Labs. As of March 2008 we have purchased common shares of stock in Netflix and Sirius XM Radio. I have a Associates Degree in Electronics Technology, FCC First Class License (in the days before it was a box top) and General Class Amateur Radio License. I was a AES Member (http://www.aes.org/) for over 20 years.

Attached is a picture of several broadcast or receiving items that I was affiliated with or I was directly responsible for: Left – 300 ft. microwave tower; at the top of the tower are microwave dishes for a 145mb/s payload statewide digital distribution systems. Down the side is a Channel 20 DTV antenna. We went on the air with ATSC Channel 20 in November 1998.

Right Top – A 10 meter satellite dish and a 8.5 meter steerable satellite dish. The 8.5 meter is for receive and Ku up-linking. We had several other small dishes for various applications.

Bottom Right – A 15 ft. Rohn tower on top of the penthouse. We had several channel specific Blonder-Tongue (commerical grade) receiving antennas on this tower.

Bottom Center – Yours truly in Post Audio siting in front of a 96 X 64 Harrison Audio Desk with a Cinema (5.1) Monitor Group. Audio & Video is my true love. I designed and help construct this room and all the loudspeakers (8). I was responsible for most equipment items at the production center and the HD mobile production trailer.

My personal home theater:

ADC Audio Spectrum Analyzer
Crown PS-400 for Sub-Woofer
Crown DC-300 for Front Main Speakers
Da-Lite Da-Snap 52 X 92 (106 Dia) with Audio Vision material screen*
Dish Network 6000 HD Satellite Receiver
Dish Network 811 HD Satellite Receiver
Hafler DH-120 for Two Back Speakers
Hafler DH-120 for Two Side Speakers
Hafler DH-200 for Front Center Speaker
Heathkit IG-1275 Lin/Log Sweep Generator
Heathkit IM-5238 dB Meter
JVC DLA-HX1U HD Video Projector*
JVC HM-DH5U D-VHS Machine
Marantz MKII IR Remote Control
Outlaw Model 970 Processor/Controller/AM-FM Tuner
Panasonic DMP-BD10 Blu-ray Disc Player
Panasonic DMP-BD55 Blu-ray Disc Player
Sony TC-RX311 Cassette Recorder
Sony ST-SE370 AM-FM Tuner
Sony DVP-S7000 DVD Player
Tenma 72-6035 Dual Channel CRT Readout Oscilloscope
URC MX-850 Remote Control with MRF-250 RF Base
X-10 Automation
Zektor HDVI5 a DVI ● S/PDIF Switcher/Selector**

HTPC with MIT MDP-120 ATSC Tuner Card/DVI Daughter Card,** Twinhan 102G Satellite Tuner Card, Samsung 710n LCD monitor, Aura Vision Keyboard (back lighted) and Mouse. Specialty Software: True Audio 1/24 Octave Analyzer, SpectraPlus 3.0 1/3 Octave Analyzer, TSReader Transport Stream Analyzer, Generic CADD, Visual CADD, Auto CAD lt, Bass Box and Box Plot Speaker Design, Cool Edit 2000 Audio Editor, Electronic Workbench and Display Mate.

Antennas: Winegard DS-3100 1M Satellite Dish (used for PBS HD), 18 X 24 inch Dish for Dish Network at 110° & 119°, 18" Round Dish for 61.5° for Dish Network. Winegard PR-9032 UHF Antenna and Winegard VHF Hi-Band YA-1713 with a Channel Master 9521 Rotor, and two Channel Master 5656 U/V Antennas in the attic. In storage: Channel Master’s 4408 FM Antenna, 3021 UHF Antenna, 4248 UHF Antenna and a Silver Sensor UHF Antenna.

*Items purchased from Jason Turk right here at A/V Science Inc.
**Items purchased from Digital Connection, a supporter of A/V Science Inc.

All loudspeakers, 19" Equipment Racks, and HTPC were designed and constructed by me. Several of my hardware items is most likely older than many people on this forum.

12-20-2005: Added HM-DH5U D-VHS Machine
04-26-2006: Added Winegard YA-1713 Antenna
11-04-2006: Added Tenma, Outlaw & URC
12-01-2006: Added Zektor HDVI5 DVI ● S/PDIF Switcher
01-07-2007: Added Panasonic DMP-BD10
01-07-2007: Removed: JVC HM-DH3000U D-VHS Machine ● Sony EP9ES Dolby Digital Decoder ● NEC AVX-910 Audio/Video Switcher/Selector ● NEC PLD-910 Dolby Pro-Logic Surround Decoder
12-05-2008: Added Panasonic DMP-BD55 Blu-ray Player

http://farm4.static.flickr.com/3312/3639689317_8172d424bc_o.png

In response to Post Number 58

A dipole antenna has the electrical equivalent of a series connected Resistance, Capacitance and Inductance. 272O j, +127O i is the rectangular values of the polar form of Z = 300O ∠25°. v(272² + 127²) = 300, T = ATAN(127/272) and is = to 25°. The plus value for i means it is inductive (if i were negative, then it would be capacitive). Absolutely nothing vague about it!!!!!

Good stuff but your notation is confusing. 'j' should always be associated with the total reactance, not the real portion of the complex impedance. That's how it is in most texts.

Good stuff but your notation is confusing. 'j' should always be associated with the total reactance, not the real portion of the complex impedance. That's how it is in most texts.

The intent was to simplify and show the Real (j, x axis) and the Imaginary (i, ±y axis) values of the complex impedance (I know j is not real). Edited to add: You are correct. I should have used R = 272Ω, Xl = 127Ω, or x = 272Ω, y = +127Ω.

Rectangular Z = 272+j127Ω, Polar Z = 300∠25°Ω


And another thing, cut me some slack, I am retired and its been 35 years since college :D :D :D. Was there a song about the J Operator or was that Smooth Operator??

PS: NightHawk, are you seeing the Greek symbols?? Some did not show in your Quote Back.

Yes, I'm seeing the Greek.
In math texts they use i for the orthagonal axis but it was changed to j for electronics texts to avoid confusion with the symbol for instantaneous current. The two should never used in the same equation. Feeling younger yet? :)

are you seeing the Greek symbols?? Symbols? Heck, it's ALL Greek to me. :D

(Ok, maybe not all of it. But it's been 25 years since I tested for my ham ticket)

Sorry. Couldn't resist.
Doc

This post addresses several areas of HDTV reception: Finding True North, ATSC Reception Test Equipment, Satellite Dish Aiming, Paint, Washers and Antenna Pictures. See attached PDF files.

Finding True North
The simple way is to use a good magnetic compass. A suitable compass can be found at your local Wal*Mart in the Sporting Goods section. You will need to account for your Magnetic Declination and that can be computed by NOAA Magnetic Declination (http://www.ngdc.noaa.gov/seg/geomag/jsp/Declination.jsp) site.

The sun can be used to find true north, go to NOAA Weather (http://www.noaa.gov) site, enter your nearest city & state, then select Local Climatology, then select the nearest location to you under the Daily Climate Reports. There should be a section that will list the Sun Rise and Sun Set times. Format three cells in Quattro (or Excel) in 24 hour time mode. Enter Sun Rise as XX:XX:XX and Sun Set as YY:YY:YY. In the third cell enter this equation: (((Sun Set-Sun Rise)/2)+Sun Rise) This will calculate your local “High Noon”. At this time a vertical (plumb) pole or object will cast a shadow on a level surface (tangent) that points due North. Note: when the sun is close to The Tropic of Cancer the shadows will be short in the USA.

The North Star will also get you close. At night, position yourself so your antenna mast is inline between you and the North Star, now mark a spot at your feet. During daylight you can point your antenna boom to the spot previously marked as your starting reference.

Problematic DTV reception:
There will be situations were receiving DTV stations will be difficult. Without proper test equipment the most one can do is place and aim their antenna by trial & error. In most cases analysis with instruments should show if reception at a particular location will be feasible. At minium, the test unit has to have a spectrum analyzer with sufficient resolution and display to show echo nulls, desired channel flatness and other signal degradation. Unfortunately these instruments are fairly expensive and beyond the reach of many (most) serious hobbyists. Listed below are several devices that are designed to analyze DTV signals. A general purpose Tenma Spectrum Analyzer is included because it is relatively inexpensive for this class of equipment. Please note this unit does not cover all the L-Band frequencies and may not be suitable for common satellite use. The Sencore AT1506 seems to be the most advanced DTV analyzer, but I think it is being phased out of their product line.

DISCLAIMER: I have no experience or affiliation with any of the devices listed below except as noted.

At work we had a Tektronix RFM151 that I used for DTV signal evaluation. It appears to be available from Tempo as the Signal Scout RFM151. This was a fine unit but the operation was not very intuitive.

Tempo Signal Scout RFM151 (http://65.36.183.19/prod_detail.cfm?cat=950&subcat=951&pid=10847), Sencore AT1506 (http://www.sencore.com/products/hdtv/AT1506RF.htm), Sencore SA 1454 (http://www.sencore.com/products/sa1454.htm), Sencore SLM 1456 (http://www.sencore.com/products/slm1456.htm), Leader LF 983 (http://www.leaderusa.com) (Has been discontinued??) Tenma 72-6696 (http://www.tenma.com) 1GHz Spectrum Analyzer. Added: BK Precision Model 2630 (http://bkprecision.com/www/np_searchmodel7.asp?lf=Spectrum+Analyzers) Spectrum Analyzer and Sencore DTU-234 RF Probe (http://www.sencore.com/products/dtu234.htm) with optional software.

Peter Putman’s comments on DTV reception, spectrum analyzers, and some antenna test. HEAVY METAL, PART I (http://www.hdtvexpert.com/pages/antoutpf), Spectrum Analyzers (http://www.hdtvexpert.com/pages/hitormisspf). More Antenna Test (http://www.avsforum.com/avs-vb/showthread.php?p=6245872&&#post6245872) by Bob Chase using a spectrum analyzer.

The file Coaxial Balun-0001.PDF contains a drawing of resistive pads to convert the 50Ω input and tracking generator output of a spectrum analyzer to 75Ω in and out. A Tapered T Attenuator and a 75Ω, 43dB Symmetrical T Attenuator convert the output of a 0 dBm, 50Ω tracking generator to 0 dBmV, 75Ω. The attenuation of the Tapered T Attenuator was chosen so the value of R2 was 0Ω and therefore eliminated. Most outs will be adjustable in 10 dB steps so you could make the Symmetrical T Pad 13 dB and set the generator to -30 dBm. The resistors should be Dale/Vishay RN60 series or better, the 1Ω could be hard to find and one may have to use a thick film resistor. The input to the analyzer has a single 25Ω resistor added in series with the input. Just add 50.5 dB to the analyzers reading to convert to dBmV, i.e., -63.7 + 50.5 = -13.2 dBmV. The operation of a 1/2λ coaxial and a ferrite transformer balun (set to ideal) is included. The 1/2λ coaxial balun is in purple and the ferrite transformer balun is in green.

Satellite Dish Aiming
Tic Mark Spacing-0001.PDF has degree markers for three common use pipe sizes. When printing this sheet make sure the “Shrink to Fit” option is not checked. A line that is 6 inches in length is at the top and is your reference, measure to make sure that it is the correct length. I print these on 24lb. paper, cutout the desired marker and attach to my dish pole. I cover them with clear weather proof tape (Frost King), see Antenna-0001.PDF for pictures.

Aim your LNB boom arm due South (those dishes with skew should be set to none or neutral skew), take a common paper clip and straighten one leg and temporally tape it to your dish incline bracket so that it is inline with a tic mark. Make a mark where the dish should be rotated to and rotate the dish so the pointer (paper clip) is at the reference mark you made (i.e., your location requires 213° W, 213-180 = 33° West rotation from due South [clockwise, looking down on the dish]). Set the elevation (and skew if multi satellite dish). If done correctly you should have a signal from the desired satellite(s). Tweak the azimuth and elevation for best signal, the skew should not be changed. For folks with small aperture dishes and using linear LNBs, set the skew of your LNB that corresponds to your location and desired satellite. Folks using an H-H motor mount should have their LNB skew set to 0°.

Satellite Dish Paint and Washers
Rust-Oleum Smoke Gray 7786 [20066 77868] paint is a very close color match to the Winegard and KTI satellite dishes that I have. This paint is very slow drying. To touch-up minor scratches I tighten the cotton of a cotton swab, spray the swab and apply.

To minimized scratching the elevation marking on my satellite dish incline brackets used to adjust the dish elevation I procured 1/4 (≤ 76CM dish) and 5/16 (≥ 1M dish) inch nylon washers and placed between the bracket and flat washers.

Pictures
Antenna-0001.PDF contains four pictures of my satellite dishes and antennas. I live in a condo and have very limited use of space. Upper Left: Winegard DS-3100 for Ku satellite (AMC-3 for PBS HD). KTI for Dish Network at 110° and 119°. Upper Right: Rear view of Winegard DS-3100. All the mounting items were fabricated by me from items available at the local building supply and online. 2-3/8, 16ga. fence post, 1-5/8 (actually 1.66") 17ga. fence post, 3/4 EMT, and treated lumber. The hardware items are: stainless steel, galvanized or Grade 8. Lower Left: Winegard PR-9032 UHF antenna, RCA dish for Dish Network at 61.5°. Lower Right: Closeup of the PR-9032.

09-19-05 Added to analyzer list
10-04-05 Added link to Bob Chase antenna test

Excellent post Wendell. The North star Polaris is @ Right Ascension 02 : 31 : 50.5 (h:m:s), & Declination +89 : 15 : 51 (deg:m:s) - pretty close.

Those spectrum analyzers seem to be $2100-3000 new, looks like there are deals on used & refurbs. Also the Tektronix RFM151 Signal Scout Cable VRF Analyzer, I guess both brands now owned by Textron.

Oil based enamels for metal are ideal for outdoor durability like the Rust-Oleum. I use same paint, also different colors & spray can:

Rust-Oleum Clean Metal Primer 12 oz spray #7780-830 white, clean metal
Rust-Oleum Clean Metal Primer rust inhibitor 1 quart #7780-504 white, clean metal
Rust-Oleum Rusty Metal Primer rust inhibitor 1 quart #7769-504 white, clean metal
Rust-Oleum Protective Enamel oil-based enamel 1 quart #7779 many colors
Rust-Oleum Professional Enamel oil-based enamel 1 gallon #7779 many colors
Rust-Oleum Gloss Protective Enamel 12 oz spray #7770-830 many colors
Rust-Oleum Gloss Hammered Metal Finish enamel 12 oz spray #7210-830 black, gold, green

Does a person need an HD antenna to HD quality reception? Or does a strong UHF and/or VHF antenna accomplish the same result?

Their is nothing special about any antenna labled HD. Since the HD channels are in the same bands as the analog channels any good antenna will do. Generally a large antenna will be better than a small one for a given band. If your analog chanels look good especially UHF, you are probably good to go. John

This thread has some of the most experienced in the antenna and cable world
and that is why I am posting my question here:

I am looking for a solution to eliminate what I believe is current coming in over
the CATV ground. There is a hum coming from the subwoofer and it disappears
when the CATV connection is removed.

I have tried a ground loop isolator, which did not work.

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=180-075

Any help would be highly appreciated.

First check to see if the CATV line into the house is grounded. There should be a grounding block or grounded splitter near where the coax enters the building. That device should have a ground wire attached which is connected to the main building ground at the other end. It should not have its own grounding rod unless that rod is bonded to the main building ground with 6ga or heavier copper wire.

The ground loop isolator most often recommended here is made by Jensen. I don't have personal experience with them.

Preamplifiers/boosters
Angle Linear PHEMT single stage preamplifier - to 20 dB, .4 dB noise (http://www.anglelinear.com/gaasfet/gaasfet.html)
Research Communications Type 9250 HDTV PHEMT LNA - 20 dB, .4 dB noise (http://www.researchcomms.com/hdtv.html)
Research Communications Type 9248 TV LNA (75 ohms) - 20 dB, .4 dB noise (http://www.researchcomms.com/television.html)
Winegard AP-4700 UHF Pre-amplifier - 19 dB, 2.9 dB noise (http://www.winegard.com/offair/pdf/Chart29.pdf)
Winegard AP-8275 UHF Pre-amplifier - VHF 28 db, 2.8 noise UHF 29 dB, 2.9 dB noise (http://www.winegard.com/offair/pdf/Chart29.pdf)
Channel Master CM-7775 preamp - 26 dB, 2.0 dB noise (http://www.channelmaster.com/Pages/TVS/TitanAmp.htm)
Channel Master CM-7777 preamp - VHF 23 db, 2.8 noise UHF 26 dB, 2.0 dB noise (http://www.channelmaster.com/Pages/TVS/TitanAmp.htm)
Kuhne Electronic broadband UHF PHEMT preamplifier - 20 dB, 1.2-2 dB noise (http://www.kuhne-electronic.de/english/preamplifier/broadband.htm)
Sitco PA24 Series UHF preamplifier - 25 dB, 1.4 dB noise (http://www.simplicitytool.com/preamplifier.htm)
Radio Shack 15-2507 - 15 dB each main amp & preamp, <4.5 dB noise (http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&category%5Fname=CTLG%5F003%5F001%5F003%5F001&product%5Fid=15%2D2507&hp=search)


Based on the above referenced notes, could one assume that the Winegard AP-8275 pre-amp is the best available..? Or, would the CM-7775 be just as good because of the lower noise number? Put, simply, what is the highest performance pre-amp available?

BTW, thanks to all who have contributed in this thread, there is a wealth of info here, I'll admit that some of it is beyond me, but a great resource nevertheless.

Thanks.

Based on the above referenced notes, could one assume that the Winegard AP-8275 pre-amp is the best available..? Or, would the CM-7775 be just as good because of the lower noise number? Put, simply, what is the highest performance pre-amp available?

BTW, thanks to all who have contributed in this thread, there is a wealth of info here, I'll admit that some of it is beyond me, but a great resource nevertheless.

Thanks.
Keenan,

That would depend on what your definition of 'highest performance' was. :)
Most of the Winegard amplifiers have the same maximum output level before signal clipping occurs. (Clipping is very bad because it will absolutely kill DTV signal while it just makes NTSC horrible to watch.) So the difference in gain between the various Winegard pre-amps is how much input signal the pre-amp can handle before clipping at the output occurs.

So if you lived in a town in the middle of nowhere, where all of the NTSC channels were very snowy, maybe the AP8275 or the more popular AP8780 would be just your cup of tea. On the other hand, if you lived fairly close to the transmitter and were using the pre-amp to overcome the losses of your attic (antenna in the attic scenario), the lower gain AP8700 would be a more appropriate pre-amp.

Another thing that is often overlooked when comparing different brands of amplifiers is how many channels the gain is actually specified for. At UHF, the Winegard specified gain is for 5 TV channels, while Channel Master uses just 2 channels to specify its gain. In Houston we have 32 channels on the air and the pre-amp sees all of them, wether we watch them or not, wether they are analog or digital. Consequently, in Houston, the higher gain pre-amps overload even sooner than the manufacturers specs would have you belive. Also, keep in mind that it only takes one channel to cause the clipping. Just one extra strong channel can cause a pre-amp to wipe out all of the rest of the channels for you. :(

For the most part, a couple of tenths a dB difference in Noise Figure (NF) can be ignored. (And again, you have to know the manufacturers method of determining it before you can start splitting dBs.) However, the difference between a 7 dB and a 3 dB NF is significant. Pre-amps tend to have a 3 dB or less NF while line amps (distribution amps) tend to be up in the 5, 6, or 7 dB NF range. I know there are folks that will disagree with me on this one but the truth is, if you live inside of 60 miles from the transmitter and the NF is less than 3 dB, don't kill yourself trying to get a lower number.

You'll find the Channel Master 7777 a very popular pre-amplifier on this forum. It performs well in the field and in many different locations and situations. It doesn't overload 'too' easily. The VHF and UHF inputs can be split for combining two antennas. The CM7775 has one flaw in that it will not pass VHF like a Winegard AP4700 will. If your area has a broadcaster that is going to go back to VHF after the NTSC kill date, then the 7775 is going to present a problem for you.

The Winegard pre-amps are less popular here but not necessarily because of any performance issues. The Winegard amps are often harder to find locally, while the CM7777 seems to be available everywhere and can be easily taken back to the store for a refund. Someday, I'll get a hold of an AP8780 and test it against my CM7777, then I would be willing to say which one has the 'highest performance'.

Bob Chase
KHWB-TV

bobchase, thanks for the reply. I should have given some additional info in my previous post.

My location is about 55-60 miles from the transmitter(Sutro Tower-SF) with two large peaks in the landscape as the crow flies so all I'm getting in reflected or bounced signals anyway. I'm currently using a CM7775 with a 91XG yagi style antenna mounted 70' in the air. I swapped out a CM4248 for the 91XG and it seems to have a bit better gain than the CM so that has prompted me to try and tweak out the rest of the system. I have considered horizontally mounting 2 91XGs but I'm not sure how much more gain that will give. Also contemplating using a horizontal plane adjuster as well. Getting expensive, but it's fun, when it works.. :)

One more note, I have a local station inline with my path to the SF tower that will consistently come close to pegging the "signal meter"...you noted that a signal may overload the pre-amp, could this station cause me problems? Will I notice if it is?

Thanks again for the input.

I posted a spread sheet, PREAMP SPECS, which summarizes manufacturer specs along with the few actual measurements that I've found published:
http://hdtv.forsandiego.com/messages/1/2846.html?1126050076
I also posted a spread sheet, DTV OVERLOAD CALC, which compares the (spec sheet) performance of several different Preamps, which can be tailored for other locations.

If you are in the Australian Outback, you might be able to use one of the high gain Preamps.
For the rest of us located within 15-30 miles of a tower, start with the lower gain models (and under perhaps 10-15 miles, better to forget it.)
Note that the new Winegard HDP-169 has a 5 dB higher overload spec than the other excellent W-G models.

Intermod products will be generated in a Preamp, even when there are moderate signal levels and strong signals will just make it worse.
These may be located on a frequency that you don't care about or is occupied by a signal that is much stronger than the interference,
in which case it may only be a problem during a signal fade event.
On the other hand, it is also likely to affect the weak signal that was the reason you bought the low noise Preamp for anyway.

The trick is to select a Preamp (and perhaps add a small attenuator on the input)
in order to maximize the SFDR (Spurious Free Dynamic Range):
http://www.tvtechnology.com/features/digital_tv/f_digital_tv.shtml
http://www.odyseus.nildram.co.uk/Systems_And_Devices_Files/Linearity.pdf
http://www.wj.com/documents/Tech_Notes_Archived/Rec_dyn_range1.pdf
http://www.wj.com/documents/Tech_Notes_Archived/Rec_dyn_range2.pdf

Thanks holl_ands, a lot of info & research! :) I subtitled the list to make it easier to navigate & added those 3 links you gave:

Amplifiers, preamplifiers & DTV info
Digital TV Signal Distortion & Interference (http://www.tvtechnology.com/features/digital_tv/f_digital_tv.shtml) 9/10/05
High Dynamic Range Receiver Parameters (http://www.wj.com/pdf/technotes/HighDynRangeRec.pdf) 9/10/05
RF, RFIC & Microwave Theory, Design (http://www.odyseus.nildram.co.uk/Systems_And_Devices_Files/Linearity.pdf) - RF... amplifier design & theory 9/10/05

Also Polaris, the North Star (if anyone's interested on positioning) is slowly moving & it's position changes slightly over the years:

Epoch/year, Right Ascension (h:m), Declination (deg:m)

1900.0 1:22.6 +88.77
1950.0 1:48.8 +89.03
1990.0 2:21.3 +89.22
2000.0 2:31.8 +89.26
2010.0 2:43.6 +89.31
2050.0 3:47.5 +89.46

with regard to the local station inline to your sf stations, you can put a quarter wave stub on the frequency of the local station on your antenna lead in.
milt

with regard to the local station inline to your sf stations, you can put a quarter wave stub on the frequency of the local station on your antenna lead in.
milt
Could you elaborate? Is this something like a notch filter? The station which pegs the meter is 22 - 516.25. I have to use the pre-amp to have a prayer of getting the distant(60 mi) SF stations, but CH 22 does not need the pre-amp as the transmitter is only 10-15 mi away. I'm concerned that this signal may overload the pre-amp and cause issues with other signals. Thanks.

Could you elaborate? Is this something like a notch filter? The station which pegs the meter is 22 - 516.25. I have to use the pre-amp to have a prayer of getting the distant(60 mi) SF stations, but CH 22 does not need the pre-amp as the transmitter is only 10-15 mi away. I'm concerned that this signal may overload the pre-amp and cause issues with other signals. Thanks.
yes it is a notch filter. quarter wave of 516.25 open end will notch out ch 22
milt

yes it is a notch filter. quarter wave of 516.25 open end will notch out ch 22
milt
Thanks, do you know where I can find such a filter? All I have been able to come up with are CATV channel specific filters, can't seem to locate any channel specific OTA RF filters.

A quarter wave stub is a tuned piece of cable spliced into the antenna feed line. It must be trimmed for the velocity factor of the coax being used which varies somewhat between production runs. You can also use a Channelmaster Join-Tenna (which come pre-adjusted to the desired channel) to notch out strong channels.
http://www.channelmaster.com/Pages/TVS/Passives.htm
The VHF models will affect adjacent channels and the UHF models will affect channels within 5 channels of the one being blocked. You can order Join-Tennas from Warren Electronics. The UHF ones need to be tuned to the selected channel so they take a couple of weeks to get in.
http://www.warrenelectronics.com/Antennas/joiners.htm

Okay, so there is no way to just notch out one channel? If I understand correctly, by using a join-tenna for CH 22, all lose 5 channels on each side of 22 as well?

The quarter wave stub, will that have a narrower notch? And if so, where do you obtain them, or do they need to be custom made....is it something you can buy, or do I need to make it myself?

Thanks

A Channel Master UHF Jointenna will generally significantly weaken two channels above and below the coupled channel, and will slightly weaken the third channel above and below, which may be inconsequential if the signals from the third channel above and below are healthy. So, depending on what channels you are intent on preserving, you might even fare better with a channel 21 or 23 Jointenna.

You can significantly weaken a single channel using a Winegard tunable, dual notch filter (UT-2700), but you will have trouble tuning it without a spectrum analyzer.

Do you need channel 22? The blocking path of a Jointenna is more of a band reject filter than a narrow notch filter, so the rejected channel that passes through it is quite often "viewable", if analog, or processable, if digital, but when you put a genuine, sharp notch filter on an analog or digital waveform, the resultant signal is often unviewable or unprocessable.

Eagle Comtronics and Microwave Filter both make inline filters that will suppress just one channel with unintended attenuation [pretty much confined to one channel above and one below. If you have found some retail dealer who will sell you a such cylindrical, "single channel trap" type cable filters, but if they will only supply them tuned to standard, cable TV frequencies, yet if they are cheap enough, you might buy a channel 73 and 74 filter and see how they do for you.

Someone selling retail makes a band reject filter that wipes out half a dozen channels that includes UHF 22, which is just 2Mz (1/3 channel bandwidth) above cable channel 73, and I think it has about 50dB of maximum depth, versus maybe 20dB for a Jointenna, so if you can find that product (Channel Vision maybe, or Channel Plus), it might meet your needs.

If time permits, I might dork around with a quarter wave stub by sourcing white noise into a coax and looking at the spectrum of the attenuated output, but that sounds more like a Ham radio solution than a broadcast TV solution. I suspect that the notch it creates would be weak and wide, and, unless you did a nice job of designing it, it might act like an antenna and pick up undesired signal.

If a quarter wave stub is what I think it is, then if you want to experiment with your own, buy a BNC "T" adaptor (maybe available at Radio Shack) and three, "F" female-to-BNC male adaptors and use that to do a neat job of tapping into the coax. Then try cutting several different, short pieces of coax to use as stubs.

If I'm doing this right, I think the quarter wavelength of channel 22 propagated through the air is just under 6", and so, figuring that RG-6 often has a velocity factor of .78 and RG-59 around .66, then I think that would make the optimal stub around 4" to 5".

Okay, so there is no way to just notch out one channel? If I understand correctly, by using a join-tenna for CH 22, all lose 5 channels on each side of 22 as well?

The quarter wave stub, will that have a narrower notch? And if so, where do you obtain them, or do they need to be custom made....is it something you can buy, or do I need to make it myself?

Thanks
A quarter wave stub is a true notch filter but it will also degrade channels on either side of the notch. A half wave shorted stub is a better solution if you aren't trying to pass VHF on the same line but any of the other solutions is probably better than a stub. I analyzed the VSWR and reflection coefficient of stubs to see how wide a notch they create. I posted the result in the local HDTV info and reception forum's antenna thread:
http://www.avsforum.com/avs-vb/showthread.php?t=381623
The reflection coefficient shows how much signal gets reflected back to the antenna instead of received. Whenever the SWR is six to one or greater a significant amount of signal is lost. I would therefore not recommend a quarter wave open stub and I would try another solution before trying the half wave shorted stub. In fact I have ordered two Join-Tennas for my brother in-law to trap the digital and analog channels from a local PAX affiliate that is blasting him but luckily he doesn't need any stations near the notch.

Note: Deleted my post concerning 1/4 wave stub filters as after submitting the post I noticed deconvolver had just posted about the same time with better info(including his post in antenna thread in reception area).

Channel Vision 3205 71-78 "notch" filter wipes out broadcast channels 20-27. I think its depth is around 50dB.

Channel Vision 3205 71-78 "notch" filter wipes out broadcast channels 21-27. I think its depth is around 50dB.
That would work, it will wipe out my ABC feed on CH 24 but that's okay. It will also help with a "strong" signal I'm getting from a transmitter further south I don't want as well.

The CM JoinTenna 21/23 I may give a try also if it has a liitle narrower bandwidth cut.

Okay, thanks, I think I know what I need to get, now are these sold by anyone other than the manufacturer? If we're talking $10-20 difference between suppliers then I don't really care, but I would hate to pay double or close to double if I don't have to.

Thanks everyone for your help.

keenan, as deconvolver said earlier, a 1/4λ or 1/2λ stub will not work very well for this application. If anyone is interested I can post the dB loss vs frequency for a stub for channel 21.

Blonder Tongue has a unit that will work, the model is MWT-U (http://www.blondertongue.com/pages/products/p_SearchResults.php?searchterm=MWT-U&Submit.x=9&Submit.y=16). This is pro gear and it will cost you. If you download the spec sheet you can see why.

Dishplace (http://www.dishplace.com/default.php/cPath/54_76?osCsid=cb72122e039a33a3a46bbfb1163f9e03) has the lowest price that I have found. You may have better luck.

I use a Winegard PR-9032 UHF antenna (very high gain) with a Winegard AP-4700 pre-amp. This pre-amp was chosen for several reasons Bob Chase has listed above. This combo was explanied in this AVS (http://www.avsforum.com/avs-vb/showthread.php?p=5821639&&#post5821639) post. Several of the TV towers are less than 20 miles away.

So performance-wise the MWT unit would be the best bet? Cost-wise the cable CH 71-78 notch filter is probably the least expensive but has a much wider band of suppression? And the CM JoinTenna 21/23 probably in between on cost and performance?

$190 is a bit steep for the MWT, but I'm not opposed to something half that price...OTOH, if the MWT is really the best tool for the job then the MWT will be the I'll get.

I'm using a 91XG from AntennaDirecT with a CM 7775 pre-amp. The towers are 55-65 miles away.

I'm also considering stacking 2 91XGs horizontally for a bit more gain and directionality. Also considering the elevation adjuster like the one shown below.

http://img.photobucket.com/albums/v637/keenanj/stacked_antenna_023.jpg

Then that's the one I'll use. I'm assuming a signal generator and 'scope could be used to tune the trap on the bench before mounting?

No, a spectrum analyzer with a tracking generator is needed to do it properly. An O'scope is not the proper device. A good RF signal generator and field strength meter would get you close.

An alternate method: Connect a cable direct to your antenna and a receiving device that has some type of signal level indicator. Tune the undesired channel and peak antenna for max level. Note the signal level. Insert the MWT-U and tune for minimal signal level.
Can this be done downstream from the pre-amp? And then I assume it should be mounted before the pre-amp for final installation?

Great! Thanks all for the help and info, I'll let you know how it turns out. :)

With an MWT-u, Keenan will be swatting a gnat with a sledge hammer, and probably missing it.

His local channel 22 is about forty degrees off his San Francisco transmission path. Unless he has been forced to misaim his antenna because of obstructions, then the signal strength coming off his antenna couldn't possible exceed 30dBmV at that angle and distance, and is surely less than that. So it is either not driving his preamp into to excessive intermodulation distortion, which, with non-adjacent channels, is usually all that we care about, or is barely doing so.

He says that his signal meter is "pegged" on channel 22. What kind of tuner does he have that gives an indication of analog signal strength? Is this really 22 analog, or is there a "22.1" digital that does not show up in the "antennaweb" table generated with Keenan's zip code? And unless it is denominated in dBmV, it is not indicative of an overload condition and gives no cause for concern. Such a primitive meter could peg at a certain S/N ratio safe signal level or some combination thereof, just as similar digital meters reach 100% when error correction is at zero yet the absolute signal strength is anywhere above maybe -50dBm, leaving lots of headroom.

If his tuner really has an analog signal meter, I'd expect it to measure just the visual carrier, which means that using it to primitively tune a notch filter would not suppress the aural carrier, which he may desire to do. To knock channel 22 down for $30 instead of for $190, what he needs to do is buy a Winegard UT-2700 (see post below) and maybe four 10dB attenuator pads. Pad down the line so that the picture is grainy, and then tune one notch to knock out the audio and the other to decimate the video. Then, remove the attenuator pads. The aural carrier of 22 analog is about 7Mz below the ATSC channel 24 pilot (San Francisco ABC), so if channel 22 analog really is 40 to 50dB stronger than channel 24 digital (which is possible), and if the problem is that the undesired channel 22 analog signal is overloading the ATSC tuner when tuning 24-digital (which I'm inclined to doubt), then he would be more concerned with attenuating the channel 22 aural carrier rather than its visual carrier, which is over 11 Mz below the channel 24 ATSC pilot.

The MWT series filters were designed a long time ago to meet certain situations for mitigating interference on analog channels. A BT MWT with both notches tuned to the same carrier attenuates it by some 60dB, but the notch, defined by its 3dB points, is very narrow (I think under 4Mz at UHF frequencies), which is important when one is trying to slightly reduce an aural carrier without degrading the quality of the color burst, but they are of limited usefulness in suppressing digital channels.

I recently had to weaken the unintended. off-axis reception of a distant station in a master antenna DTV reception array. I used an old Channel Master dual, vernier UHF trap. Its notches are no where near as deep as the MWT notches, which, by itself, is not really a problem in most digital applications, since the capture ratio of the desired DTV signal is pretty low. I don't know how low, but it is well under 20dB. Anyway, the dual notch left me with three peaks across the plateau, which meant that, by that one measure, its performance was inferior to what a Jointenna could do for me.

But unfortunately, the Jointenna cases leak like sieves and this installation was less than two miles from another DTV transmitter, so if I used the Jointenna, I would have been leaking in another undesired signal. I therefore stayed with the Channel Master trap. (Note: the UT-2700 also has a plastic case, and invites ingress problems in urban situations). I'm going to have someone custom make a solid channel 45/46 band reject for me, which is not that difficult to construct because that coax only needs to pass channel 39 and below, and channel 50 and above. In fact, I just might order channel 39 low pass and channel 50 high pass "tier traps" to accomplish the same thing.

Keenan also has Univision on his intended target line broadcasting on DT 47 and an analog 68 at a distance of maybe 20 or so miles. I would worry about those more.

With all the money he'll be saving with the Winegard UT-2700, he can buy a channel 68 Jointenna and a channel 47 (or better yet, a channel 49) Jointenna and use them as channel suppression filters. A channel 49 Jointenna will knock his channel 47 down by maybe 10dB, which is as much suppression as he could possibly need, but will leave his channel 45 UPN from San Francisco unscathed. With each Jointenna, put an F-75T terminator on its "single channel input" port and use the other two ports to form the band reject filter. Then, mix and match them with your tuned Winegard channel 22 analog reject filter. There will be eight permutations in all. For each permutation, record the so-called "signal strength" numbers for the San Francisco DTV stations. Unfortunately, these need to be inserted between the antenna and the preamp, since the objective here is to see if reducing any of those inputs reduces the debilitating effect of intermodulation distortion in the preamp. Then, use just the one, two or three of these components that optimizes the San Francisco signal level numbers.

...Most of the Winegard amplifiers have the same maximum output level before signal clipping occurs. (Clipping is very bad because it will absolutely kill DTV signal while it just makes NTSC horrible to watch.) So the difference in gain between the various Winegard pre-amps is how much input signal the pre-amp can handle before clipping at the output occurs.

...Another thing that is often overlooked when comparing different brands of amplifiers is how many channels the gain is actually specified for. At UHF, the Winegard specified gain is for 5 TV channels, while Channel Master uses just 2 channels to specify its gain. In Houston we have 32 channels on the air and the pre-amp sees all of them, wether we watch them or not, wether they are analog or digital. Consequently, in Houston, the higher gain pre-amps overload even sooner than the manufacturers specs would have you belive. Also, keep in mind that it only takes one channel to cause the clipping. Just one extra strong channel can cause a pre-amp to wipe out all of the rest of the channels for you.

With most modern amplifiers, each time you double the number of input channels of equal strength, the maximum output level of the preamp goes down by 3dB, so if a preamp can output 51dBmV with a three channel load, then it can only output 48dB with a six channel load.

Some amplifiers of inferior design can't handle large channel loads at all. For example, the popular Tru Spec TA-25's maximum output seems to drop by 8dB or more every time the channel load is doubled. They are therefore absolutely useless as cable TV amplifiers.

I don't think that the problem with preamplifiers, when overloaded, is clipping, as much as it is intermodulation distortion. If clipping were the problem, then the analog channel on which the symptom would first and most severely appear would be the strongest channel, when, in fact, it is the weakest that first suffers.

I know of no way to measure intermodulation distortion, so I just have to accept the manufacturer's specs regarding it on faith, just as I do when I design complex satellite intermediate frequency distribution systems. We try to keep something called Third Order intermodulation distortion developed intermediate frequency satellite signal RF distribution below -40dBc. We do so because the manufacturers of the receivers say to.

Spaun, a major supplier of commercial RF distribution products, rates the maximum output of its products in microvolts, such that their amplification products will not exceed -35dBc in 3rd Order IMD with a one "channel" load, so first, we subtract 108.75 to convert to dBm, then we subtract either 12 or 15 dB depending on whether the load is 16 or 32 transponders, then we derate it by another 2.5dB to further reduce the 3rd Order IMD from -35dBc to -40dBc because for each dB the input goes down, the intermodulation distortion goes down by 2dB. Spaun references their products to -35dBc because that is the benchmark level for analog picture quality, sort of like 46dB S/N ratio is for picture quality.

Then, if there is a second amplifier in cascade with the first, we have to further limit the 3rd order IMD developed at each stage to -46dBc, because it goes up by 6 dB every time we double the number of amplifiers in the cascade.

Broadcast frequency distribution amplifier manufacturers publish specs for Composite Triple Beat, Cross Modulation and Composite Second Order intermodulation. As long as we use only one amplifier, we don't need to concern ourselves with the implications of those ratings, but when we cascade them, we do have to consider them.

As far as I know, the major manuacturers of cable TV RF amplification equipment are still rating their equipment based on the peak signal strength of analog carriers. About three years ago, I spent half a day on the phone talking to the technical service departments of several major manufacturers, trying to get them to estimate what kind of digital, RMS signal levels would develop undesired intermodulation byproducts that would exceed any industry recognized arbitrary standard for their amplifiers. I might as well have been talking to them in Chinese. In fairness to the manufacturers, they surely don't assign the task of answering telephone queries to their design engineers, but it bothers me that I am still "flying in the dark" when I attempt to estimate the maximum loading of my distribution amplifiers that have mixed digital and analog loads.

When I view the "+1" digital channels in my market (45/46, 50/51 and 56/57) on my BTSA-5 spectrum analyzer, I observe that, visually, the digital plateau is about 20dB below the lower adjacent channel visual carrier when I set my spectrum analyzer at a 1Mz bandwidth. Figuring that the bandwidth correction factor would bring the actual, 6Mz value of the digital signal up by about 8dB, I then try to set the rest of the digital channels at the same level or slightly below.

How much do those digital channels further load the amplifier? Beats me! They obviously contain a lot more RF energy than do analog signals of the same nominal voltage level, but I don't know how to combined these unlike terms for calculating amplifier loading.

I typically set up a headend such that the three or four strongest analog channels are at a level such that, if they were the only load present, then the launch amplifier output would still be a few dB below its maximum rated output for that load, and then I add about a dozen digital signals that are 15 to 20dB below that level, and then there are half a dozen additional analog signals at levels about 5 dB or so below the strongest analog signals.

I haven't yet experienced any symptoms of amplifier overloading, which is to say, I have never had a resident's receiver fail to process signals that I could process at the headend, but still, I'd surely like to be able to better calculate my distortion power ceilings because there are some large buildings I design broadcast HDTV headends for existing distribution where I need to deliver every dBmV I can to make sure the signals reach the bottom floor units, but right now, I generally do not exceed levels of about 55dBmV analog and maybe 35dBmV digital at 700Mz. But since these signals are being fed into loop systems that were engineered for 60 to 66dBmV VHF input signals, they sometimes result in grainy analog UHF pictures on the lower floors. If the UHF signal levl drops to, say, -15dBmV analog peak at 700 Mz, then the RMS digital signal level at that point would typically be about -35dBmV. In that situation, the UHF analog looks horrible, but the digital signal strength is still sufficient as long as they don't get piggy and split it, but I need a greater launch level than I feel I can safely develop presently, otherwise I have to keep all of the internal wiring perfect, which is not always practical.

I pay $19 each for UT-2700s, but you can't buy them where I do. Here is a web page that lists them for under $30:

Winegard UHF TV Antenna Off-Air Signal / Frequency Trap, Variable, Part # UT-2700, UT2700
Item No.: TRPW27
Price: $29.95 (http://www.summitsource.com/winegard-variable-uhf-trap-part-ut2700-ut2700-p-5344.html)

And here is someone who lists Blonder Tongue MWT-U Notch Filters (http://www.advmicronet.com/products/product_info.cfm?Product_ID=8630) for just $111.55, which is about what I would pay to the vendor I would likely buy them from, but I don't know if this company sells retail.

AntAltMike, thanks for those posts. I'm on my way to the dentist so I don't have time to digest them them yet but I can give you a bit more info. The "signal meter" I'm using is the one in a Dish 942 sat receiver so no doubt it's not entirely accurate for what I need to do. What it tells me is that when tuned to 22.1 or 22.2 the graph style meter is pegged at 100%. I can get a couple of Sutro stations at around 50-65%. The station is KCRB with analog 22 and digital 22.1 and 22.2. And you're right about 47 and 68, they are also strong as well but not as strong as 22.

My actual location is,

Lat 38.4473457
Lon 122.6992493

I don't recall what Sutro Tower or San Bruno Mt transmitters are at but those are the 2 I'm mainly concerned with.

Attached is a PDF map of the transmitter locations in the SF bay area.

AntAltMike, thanks for those posts. I'm on my way to the dentist so I don't have time to digest them them yet but I can give you a bit more info. The "signal meter" I'm using is the one in a Dish 942 sat receiver so no doubt it's not entirely accurate for what I need to do. What it tells me is that when tuned to 22.1 or 22.2 the graph style meter is pegged at 100%. I can get a couple of Sutro stations at around 50-65%. The station is KCRB with analog 22 and digital 22.1 and 22.2. And you're right about 47 and 68, they are also strong as well but not as strong as 22.

My actual location is,

Lat 38.4473457
Lon 122.6992493

I don't recall what Sutro Tower or San Bruno Mt transmitters are at but those are the 2 I'm mainly concerned with.

Attached is a PDF map of the transmitter locations in the SF bay area.
Digital receiver graphs don't really show signal strength so you can't tell if KRCB's signal is too strong or not. Some ways to reduce overload are to use a lower gain more overload resistant pre-amp like the Winegard AP-8700 (as long as the receiver doesn't overload) or to use antenna directivity to reduce the interferor. You have 30 degrees between KRCB and the SF towers, with a horizontal stack you could adjust their spacing until KRCB is notched while pointing towards the SF towers. I think that spacing would be at 300/524*(0.5)/sin(30) meters or about 22.5 inches center to center (it's OK if the reflectors overlap a bit). KRCB is at 22 analog and 23 digital (which re-maps to 22.1 & 22.2). So to reduce its power a filter would need to notch both channel's 22 and 23. A Join-Tenna for channel 23 would work and probably only affect channels 19 and 27 slightly if at all. Here is a list of the digital channels near you, note that the reciever will re-map the channel number to the old analog number with -1 or -2 appended etc:
http://www.fcc.gov/fcc-bin/tvq?state=&call=&arn=&city=&chan=&cha2=69&serv=DT&type=0&facid=&list=2&dist=100&dlat2=38&mlat2=26&slat2=50&dlon2=122&mlon2=41&slon2=57&size=9

I alluded to this in Post # 89 (http://www.avsforum.com/avs-vb/showthread.php?p=6177401&&#post6177401) by stating what I was using and why. keenan did not seem interested so I did not pursue any further.
It's not that I wasn't interested, I'm just trying trying to absorb all the info presented. I freely admit that a lot of this is over my head. I know see that you gave that info because the towers were close. When I originally read it, I saw the reference to 20 miles and since my desired stations are at 50-60 miles I did not give it the attention it deserved. :)

I really do appreciate all the info all of you have presented and I'm just trying to consolidate everything down into an approach I should take. My antenna is 70' in the air on top of a tree so trips ups and down need to be at a minimum.

I haven't purchased anything yet so what I do is still on the table. It may very well be that the channel in question is not harming reception of the further located stations and I guess my original query was if steps could be taken to insure that it doesn't.

I think at this point, I will go with dual 91XGs stacked horizontally and spaced as deconvolver suggests, and I'm probably leaning toward the JoinTenna for ch 23.

Would the ability to adjust the horizontal plane remotely be of value? The cost to do such would be around $350. Money is not an issue if the functionality increases at least somewhat. Of course it's impossible to say would it be worth it, I suppose I'm asking simply is it a worthy modification?

I have no line of sight whatsoever to the SF towers, and probably not to the CH 22 tower either, so everything I get is bounced from somewhere.

As far as Keenan and his Cheshire channel 22.1 are concerned, I have good news and better news. The good news is, according to Antennaweb, channel 23 DTV/22.1 doesn't exist. Even when I punched in Cotati's, California's zip code.

The better news is, the FCC says it does exist but is only transmitting at 67 KW, so there is no way that it is overloading his preamplifier or tuner and should be of no concern to him.

Twenty miles isn't close when a transmitter is 40 degrees off target and transmitting at 67 KW. You should only be thinking about mitigating channels 47 and 68, regardless of what your signal meter scale says. You don't know how strong 68 is because it is analog, and your signal strength indicator saying that 47 is "weaker" than 22.1 is not measuring actual strength, such that it might adversely affect a preamplifier or tuner.

The people here who have installed tilters have enjoyed playing with them, but I don't think anyone vouches for them.

What aren't you getting reliably from San Francisco?

Back to the drawing board guys....there are over FIVE nearby UHF transmitters with significant levels...

By checking ALL four boxes on the right side of the fol site, you can find ALL of the local transmitters:
http://www.2150.com/broadcast/default.asp
Suggest you limit the search radius to about 30 miles, otherwise it times out.

There are two analog UHF transmitters listed only a few miles away (repeater and a so-called "low power"):
UHF CH25: K30DO (aka K25HI), 25.8 deg, 4.7 miles, 17 kW ERP, 17 kW Max, 547 m AMSL.
UHF CH36: KTVJ-LP (Fiori Media), 25.8 deg, 4.7 miles, 21.3 kW ERP, 50 kW Max, 547 m AMSL.

Note that there is an antenna tilt mod for KTVJ-LP listed, reducing ERP (towards horizon) to 21.3 kW,
but the maximum power in all H and V directions is still 50 kW....no doubt directed downwards towards Keenan.

Note KRCB-DT (and KRCB-TV) filed Construction Permits to relocate with different antenna patterns and beam tilt:
UHF CH23, KRCB-DT (Rural), 135/136 deg, 9.5/9.6 miles, 4.7+ kW ERP, 110 kW Max, 800m AMSL.

The downward antenna tilt situation also applies for fol. nearby station:
UHF CH28: KDTV-CA (Sta Rosa), 17.5 deg, 15.1 miles, 8.2 kW ERP, 109 kW Max, 1219 m AMSL.

If you really want to know how high the receive signal levels are, I suggest you look at the below spread sheet.
Note that I did not calculate the "Add'l Loss" for those towers that are not Line-Of-Sight,
nor the XG-91 antenna pattern as you point towards different stations.
So there is still work for the interested student....

Given that Keenan already has a tall mast, has already tried one of the best 8 bay bowties and one of the best "yagi(s) with corner reflectors", has a nice, high gain, high powered preamp with little liklihood of amplifier or receiver overload, yet he is generally dissatisfied, across the board, with his distant, San Francisco reception, which, he believes, does not enjoy line-of site predictability, there just isn't any reliable way to improve his reception. He might be better off "borrowing" different receivers and seeing which one seems to most reliably lock onto the signals that he now has.

He can cheaply rule out preamp overload with the trial insertion of 22/47/68 Jointennas. I think I pay $24 each for them. I don't know what retail is, but they will definitively settle the issue of whether he is suffereing from preamp overload fairly cheaply.

He can also buy an analog FSM on eBay for twenty bucks to take out the guesswork regarding the signal strength of undesired signals.

The hi-gain CM-7777 is definitely OVERLOADED, and the antenna sidelobes aren't enough to cure the problem,
esp given that signals will also bounce back off nearby hills.

Recommend using a lower gain Preamp, such as the Winegard HDP-269 which has 3 dB Noise Figure,
12 dB Gain (just enough to overcome the coax downlead and HDTV Noise Figure)
and has 11.5 dB HIGHER overload specs that the already excellent W-G AP-4700 (or equal) Preamps.

=======================================================
I did quick Line-Of-Sight check using Google-Earth.
All the nearby stations, except perhaps KTLN are LOS to Keenan's location.
I would guess a moderate amount of "Add'l Loss" due to diffraction from KTLN (under 10 dB?) and Sutro Towers (under 20 dB?).
But if you really want to know, I suggest RADIO MOBILE (for Windows) or SPLAT! (for Linux):
http://hdtv.forsandiego.com/messages/1/2846.html?1126050076

Using the exact lat/long from FCC database, you can actually see the towers
or in some cases the ground preparation work since some of the photos are fairly old.
Google-Earth can be off by several minutes from the posted lat/long due to coordinate "datum" differences (FCC's NAD 27 vs WGS84):
http://www.keyhole.com/GoogleEarthHelp/GoogleEarth.htm
[So Keenan is probably not living in a tree house.]

....there are over FIVE nearby UHF transmitters with significant levels...

By checking ALL four boxes on the right side of the fol site, you can find ALL of the local transmitters:
http://www.2150.com/broadcast/default.asp
There are two analog UHF transmitters listed only a few miles away (repeater and a so-called "low power"):
UHF CH25: K30DO (aka K25HI), 25.8 deg, 4.7 miles, 17 kW ERP, 17 kW Max, 547 m AMSL.
UHF CH36: KTVJ-LP (Fiori Media), 25.8 deg, 4.7 miles, 21.3 kW ERP, 50 kW Max, 547 m AMSL.
...


The hi-gain CM-7777 is definitely OVERLOADED, and the antenna sidelobes aren't enough to cure the problem,
esp given that signals will also bounce back off nearby hills.

Which transmitter(s) are you saying are overloading it?

I wasn't able to use the linked transmitter locator because I don't have Keenan's map coordinates, but I Googled the Santa Rosa, California zip code and determined, via Antenna web, that the Sutro Tower is at a bearing of 145 degrees and the channel 22/23 transmitter is at 108 degrees. The channel 22(23) tower is therefore 37 degrees off targetline. The reception antenna gain of 22/23 will be down by somewhere between 10 and 20dB, most likely, 15dB down or more.

The two local, low-power transmitters that holl_ands has indentifed, at around 25 degrees, are about 120 degrees off-targetline to the rear, meaning the gain of them is down over 20 dB using either the 4228 or the screen-reflected Yagi.

The 7777 has a maximum output of 51dBmV for a two channel load, 47 for four channels and 42 for eight channels. But that refers to equal strength channels. This antenna receives the equivalent of a two or three channel load, maximum. Does anyone remember what a "block tilt" was and is? Blonder Tongue and others used to advise that you could increase your VHF highband channels by 2dB if you also lowered all your low band channels by 4dB. But you only got to do that once. If you instead eliminated the VHF lowband channels all together, you would only raise the highband maximum output by 3dB. But if you then eliminated half the VHF upper channels (not that doing so would ever be beneficial), the maximum output went up by another 3dB

The San Francisco signals are insignificant to the loading estimate. Therefore, this preamp doesn't even begin to excessively intermodulate until the one "pig" carrier output goes somewhere over 50dBmV, which means that its input is over 24dBmV. And even then, that is the level at which an analog picture might begin to show imperfections that initially can only be seen by those who know a TASO Grade 1 picture. The overloading input would have to be several dB higher than that to start breaking up the digital signals.

A low power transmitter five miles away hitting the rear oblique of a screen-reflected antenna will not develop 20dBmv. The only potential threat is the channel 68 that is on line but twenty miles away, and even then, it is not really powerful for that high a frequency, having an output of only 1,000KW.

Which transmitter(s) are you saying are overloading it?

I can't use the linked transmitter locator because I don't have Keenan's map coordinates.
Lat 38.4473457
Lon 122.6992493

BTW, all this attention is making me feel like a very important person so I'll say again, I do appreciate all the input, very much. I look at this as a challenge to try and get the best that is possible.

I'll need to read the last several posts later as I'm off to dinner, but if any additional info from my end is needed, please ask.

Thanks

P.S. If you all feel my particular situation would be better served in another thread and not pollute the focus of this one, please say so.

BTW, all this attention is making me feel like a very important person so I'll say again, I do appreciate all the input, very much.
Nah, just a bunch of bored guys ;).

Attached is the Digital & Analog stations out to 70 miles Added: for keenan.
.

Back to the drawing board guys....there are over FIVE nearby UHF transmitters with significant levels...
...
If you really want to know how high the receive signal levels are, I suggest you look at the below spread sheet.
Note that I did not calculate the "Add'l Loss" for those towers that are not Line-Of-Sight,
nor the XG-91 antenna pattern as you point towards different stations.
So there is still work for the interested student....
The transmit and receive beampatterns and diffraction losses are important for the low power stations. KTVJ is transmitting in a different direction and all the low power stations are in a completely different receive direction from San Fran so the receive beampattern will be low towards them. The low power stations are also not mounted on high towers so diffraction losses could be significant. All together I don't think the low power stations are a likely overload problem. That leaves KRCB and KTLN as the main overload possibilities. Strong reflected paths from very different angles than the direct path are possible but unlikely so direct path directions are the main threat. The current configuration probably doesn't have severe overload because his performance now for the distance is pretty good- but a slight overload is a possibility. If overload does exist then I would expect any one of the following remedies would likely eliminate it: A horizontal stack with a null towards KRCB plus a Join-Tenna for KTLN if needed, channel 23 and/or channel 68 Join-Tenna's with the unneeded input's terminated, replacing the CM 7777 with a WG 8700 or 4700 or 2870. Note that the horizontal stacking distance is not super critical to eliminate KRCB (ex. 24 inches instead of 22.5 inches should be OK but my original math needs to be checked), just steer to place the null for minimum interference and the main-lobe should be close enough to San Fran. The horizontal stack has the advantage of additional gain as long as a low loss coupler is used. The Winegard pre-amps have the disadvantage of slightly poorer performance than the 7777 in the absence of overload and the Join-Tenna is not well shielded and will add some loss for channels near the "null". One thing that could be tried with the WG pre-amp and Join-Tenna's is to put the Join-Tenna's in the house between the Pre-amp output and a low noise low gain distribution amp. That may help overcome lead-in losses which is especially useful if the receiver has a poor noise figure. I agree though with AntAltMike that once overloading is ruled out there is probably no reasonable way to get a big improvement from the current performance. (edited to add KTLN as an interference possibility)

P.S. If you all feel my particular situation would be better served in another thread and not pollute the focus of this one, please say so.

Good Idea. I deleted all my post in this thread that did not contain "DIY Info, How 2's or Links"

OK kennan, from the top, you have:

Lat 38.45 North
Lon 122.70 West or -122.70

91XG Antenna at 70 ft.
Antenna Rotor
Channel Master 7775 Pre-Amp
Dish DVR-942

Problem? Objective?

I just saw your antenna mounting. If you have very much antenna movement with wind there will be a high probability of picture problems on the DTV stations.

Good Idea. I deleted all my post in this thread that did not contain "DIY Info, How 2's or Links"

OK kennan, from the top, you have:

Lat 38.45 North
Lon 122.70 West or -122.70

91XG Antenna at 70 ft.
Antenna Rotor
Channel Master 7775 Pre-Amp
Dish DVR-942

Problem? Objective?

I just saw your antenna mounting. If you have very much antenna movement with wind there will be a high probability of picture problems on the DTV stations.

Also have an ATSC tuner in my Mits WS73615 and one in a DirecTv HD-TiVo unit although the Dish unit seems to be the best of the bunch.

Yes, the tree mount is not ideal but I don't really have any alternative as I'm surrounded by them and a metal tower would probably prove to be to much effort and expense.

Essentially my goal here is to maximize reception of digital channel 45.1 KBHK from Sutro Tower-SF as it's the only channel I desire that is not provided any other way(sat-cable), and secondarily, I enjoy trying to get OTA signals, not really a hobby, but it's fun and interesting to try.

The signal I get now is around 60-70% on the Dish meter. Usually at the lower end of that range and there are complete drop-outs as well at times. If I could improve that signal say another 5-10% I would have a solid reliable signal. The complete dropouts are a nuisance but I doubt there is much I can do about that as I'm guessing the cause of those are out of my control.

DETAILED OVERLOAD CALCULATIONS FOR KEENAN'S LOCATION:

The below spread sheet shows that the CM-7777 will be overloaded if antenna is
pointed to any of the local stations. The HDTV Tuner may also be overloaded.

When pointed towards Sutro Towers with one of the sidelobe notches pointed towards
A-KRCB and KRCB-DT (9.5 miles away), the CM-7777 will be overloaded by KRCB-DT.
Also overloaded by A-KTLN and KTLN-DT, that are directly on the line to Sutro Towers.
The HDTV Tuner may also be overloaded, but can be avoided by inserting attenuation
on the Tuner input (e.g. RF Splitters or R-S Variable RF Attenuator).

Note that the sidelobe notch is much deeper for A-KRCB on CH51 (I assumed 20 dB)
than it is for KRCB-DT on CH23 (I assumed 10 dB).
Since I have not seen antenna pattern measurements or NEC simulations for the
XG-91 type antenna, I assumed that it was similiar to the high-gain CM-4228 antenna,
using NEC Sim results found in www.hdtvprimer.com/ANTENNAS/comparing.html.

When the specs for the new Winegard HDP-269 were entered, all of the Preamp
overload problems were not only cured, but the input signal was 15-20 dB below
the specified overload point, which maximizes the Spurious Free Dynamic Range
so that intermods are pushed down towards the noise floor. This facilitates
reception of the weakest signals from remote locations.

With only 12 dB of gain in the HDT-269, the input level to the HDTV Tuner was still
uncomfortably close to what I have seen specified for maximum input levels.
This can be avoided by inserting a small amount of attenuation prior to the Tuner,
e.g. RF Splitter(s) and/or a R-S Variable RF Attenuator.

I didn't take the time to tailor RADIO MOBILE for the S.F. area, so some of the path loss
numbers are "best guesses" based on performing similiar runs in LA and San Diego area.
So there is still a useful exercise left for the interested student....

Let me know if you find any errors in the spread sheets....no really...

ERRATA:
================================================
1. Found a small error in the Off-Beam Rcv Ant Gain when pointed towards
Sutro Tower and using W-G HDP-269 Preamp.
Now it's the same as for CM-7777, which was correct to begin with.

===============================================
2. deconvolver found an error: A-KRCB should be CH22 (vice my KUSI on CH51).
This also changes the Antenna Gain and Off-Beam notch depth, resulting in
a stronger overload contribution. A-KRCB is the second strongest overload source
and KRCB-DT is still the strongest overload signal when pointed toward Sutro Towers.

3. The KTLN-DT and A-KTLN broadcast antenna gain corrections (voltage not power) were incorrect.
This results in reduction in the overload contribution from these stations by several dB,
but they remain lurking just below the CM-7777 spec overload level.

4. In double checking, I found that KDTV-DT should be A-KDTV, which deletes
the 8 dB Average to Peak Power conversion.
This wasn't the principal problem before and is even less so now.

==============================================
I also added calculations for the W-G AP-4700 (or equal) Preamp:
RevC spread sheet has been replaced by RevD:

I keep getting "Internet Explorer Can't Open...", and, "... Cant Find..." messages when I try to open the spread sheet.

I can't find any overload specs for the HDT-269. What are they?

Winegard's specs chart for their other amplifiers doesn't specify the channel loading. It seems to me that the channel loading figure used to be on that chart. Does anyone know what it is?

Holl_ands analysis assumes that Keenan's antenna performed like a 4228, which is an 8-bay bowtie, but it looks more like a 4248, which is even less favorable for his situation, since the off axis rejection of a corner reflector Yagi is not as great as the 8-bay bowtie.

I had assumed that the channel 22 transmitter was 15 miles away, the channel 68 was 22 miles away, and that the angle between them was about 40 degrees. But from the map coordinates, channel 22 is just 9.5 miles away, and the angle between the desired and undesired transmissions is just 30 degrees.

Let's assume that his antenna has a net gain over isotropic of 12dB at channel 22 and 16dB at channel 68. In order to violate the input threshold in a two channel analysis, either both of those channels would have to develop 25dBmV coming off the antenna, or perhaps one could be 27dBmV with the other about 21dBmV

Roughly figuring, channel 22 is 10 miles away and 30 to 40 degrees off axis, and has a transmitter power of, I believe, 65Kw. If the 30-40 degree off-axis antenna gain "discount" at channel 22 is 10-15dB, rather than 15-20dB as I had speculated in my estimate, then the antenna is going to net somewhere in the range of -3dB to +2dB relative to isotropic. Will a 65Kw signal develop twenty-something dBmV of signal power at that distance with effectively negative antenna gain?

Now, Telemundo channel 68 analog, 47 digital is another matter. 16dB of antenna gain on channel 68, 21 miles of dissipation and 1,100Kw analog. That's the one I expressed concern about in my earlier posts. That's the one that is getting Keenan's system in trouble.

Channel Vision or Channel Plus has a lowpass filter that rolls off somewhere around 750Mz, with an insertion loss of no more than 1dB. That should scrape off channel 68 nicely.

The Telemundo channel 47 digital is transmitting at 220Kw at present, but it will get increased to 1000Kw. Assuming that Keenan doesn't habla espanole, the WT-2700 should neatly mitigate that one without touching his precious 45 UPN from San Francisco.

What is Holl_ands using for receiver minimum and maximum input levels? I'm going to be working on top of a nice tall building, just three or four miles from some DTV towers this weekend (Ritz Carleton, corner of 23rd and M St, NW, 20037, if anyone wants to develop a spreadsheet that I can take with me). I'm going to have an early Samsung tuner and one of those receivers that Radio Shack just closed out on (Accurian?) and will feed some strong and weak filtered signals into them to see how far I can exceed the input thresholds on both the low and high ends.

(note: edited to incorporate distances and angles from the FCC page linked in deconolver's post #101)

I just got the same error clicking on above zip file. Always worked in the past....
Sometimes I get a "Cannot find file" error when clicking on pdf files.
In both cases, I can Right Click and use "Save target as...." selection to save file.

=======================================================
I couldn't find HDP-269 on Winegard Website, but is for sale from usual sources:
http://www.warrenelectronics.com/antennas/hdp269.htm
http://www.solidsignal.com/prod_display.asp?PROD=ANWHDP269
http://www.summitsource.com/product_info.php?ref=1&products_id=5577
http://www.summittvantenna.com/category66.html

========================================================
If you look at hdtvprimer.com NEC plots, you'll see that the +/- 30 deg side-lobe depths aren't
all that much different for all of the listed high gain antennas: CM4228, CM4248, DAT-75.
What will change a little bit is the exact angle of the notch for mid to high frequencies,
with narrower beamwidth antennas having a corresponding smaller angle to the notch.
For all of the listed antennas, the notch was very shallow for the low frequencies.
Since I haven't seen anything published on the XG-91 type antennas from over half
a dozen different vendors, we're left with doing the best we can with what we have.
The angle of the sidelobe notches for the XG-91 type antenna is probably a few degrees
less than the CM4228, due to the slightly higher gain and hence narrower beamwidth.

For Keenan, small changes in direction are needed in order to "aim" the notch
towards A-KRCB and KRCB-DT. You might try both the Analog and Digital
station to see which one demonstrates the "worst" signal indicator.
The antenna beamwidth towards Sutro Towers is specified to be 36 degrees for low frequencies
and 22 degree for the high frequencies, so there is a moderate amount of wiggle room.

I used 20-26 dB F/B specs found on the Dipol website for their ATX-91 antenna.
Note their Gain is in dBi (subtract 2.15 for dBd):
http://www.dipol.com.pl/esklep/a3710.htm
They also have the best picture for the generic 2.22 meter, 91 "element" antenna
that is sold worldwide under many different names from many different sources.

So do you have anything better than Dipol and Funke websites for XG-91???

I would be very wary of any F/B or sidelobe notch claims in excess of about 20 dB.
[I saw some F/B specs as high as 32 dB for the XG-91 type antenna!!!]
[Can't be average. Maybe the absolute best value for an extremely narrow rear angle???]
You might see > 20 dB in a NEC sim run or even in an idealized plot from the manufacturer,
but real world systems mounted in the vicinity of nearby objects will tend to fill in the nulls.

========================================================
I searched...and I searched....and I searched for specs on ATSC Tuner Modules.
Such as it is, the ATSC_NTSC TUNER MODULE SPECS spread sheet is posted
(along with everything else of interest on this subject) at:
http://hdtv.forsandiego.com/messages/1/2846.html?1126050076

In all of my searching for DTV Receiver performance tests, I have yet to find any
meaningful overload and intermod tests on Preamps and HDTV Receivers.

For what's it's worth, Charles Rhodes reverse engineered the intermod characteristics
for the 1st Generation Zenith Receiver, concluding that the double conversion tuner
has an Output Third Order Intermod Intercept of OIP3 = +14 dBm:
www.tvtechnology.com/features/digital_tv/f_digital_tv.shtml
Hardly anyone makes double conversion ATSC Tuners. Only one in list is by Samsung.
If you check the available "state of the art" in my PREAMP SPECS spreadsheet,
you'll see that the OIP3 was pretty mediocre.

====================================================
Wouldn't it be great if the AV rags would conduct meaningful equipment tests on DTV equipment????
It would also be very retro if the manufacturers would actually publish meaningful specs.

DETAILED OVERLOAD CALCULATIONS FOR KEENAN'S LOCATION:

The below spread sheet shows that the CM-7777 will be overloaded if antenna is
pointed to any of the local stations. The HDTV Tuner may also be overloaded.

When pointed towards Sutro Towers with one of the sidelobe notches pointed towards
A-KRCB and KRCB-DT (9.5 miles away), the CM-7777 will be overloaded by KRCB-DT.
Also overloaded by A-KTLN and KTLN-DT, that are directly on the line to Sutro Towers.
The HDTV Tuner may also be overloaded, but can be avoided by inserting attenuation
on the Tuner input (e.g. RF Splitters or R-S Variable RF Attenuator).

Note that the sidelobe notch is much deeper for A-KRCB on CH51 (I assumed 20 dB)
than it is for KRCB-DT on CH23 (I assumed 10 dB).
...
New RevC spread sheet is now available:
You show A-KRCB as channel 51 but it should be channel 22 so one notch covers both the analog and digital stations. Also the distances and angles to all Keenan's stations can be found here:
http://www.fcc.gov/fcc-bin/tvq?state=&call=&arn=&city=&chan=&cha2=69&type=0&facid=&list=2&dist=100&dlat2=38&mlat2=26&slat2=50&dlon2=122&mlon2=41&slon2=57&size=9

I can't find any overload specs for the HDT-269. What are they

I couldn't find HDP-269 on Winegard Website, but is for sale from usual sources:
http://www.warrenelectronics.com/antennas/hdp269.htm
http://www.solidsignal.com/prod_display.asp?PROD=ANWHDP269
http://www.summitsource.com/product_info.php?ref=1&products_id=5577
http://www.summittvantenna.com/category66.html

All four of those linked sites selling the HDP-269 copied the same consumer data sheet, which says that the "Maximum total input" is 350,000 microvolts. Correct me if I'm wrong, but I don't think that maximum input levels can be usefully denominated in unreferenced, cumulative microvolts. We've got to work some "squares" or "square roots" into the tallied inputs to reflect the fact that, if you halve the voltage, you reduce the power consumption by 75%.

Winegard's specs chart for their other amplifiers doesn't specify the channel loading. It seems to me that the channel loading figure used to be on that chart. Does anyone know what it is?

Winegard's channel loading standard, which HDTVPrimer has inadvertently excised from the table it copied, can be found in Winegard's own 1996 catalog #215 on page 14. They claim that their UHF preamps don't exceed 0.5% Cross Modulation with FIVE CHANNEL UHF INPUTS of 30,000 microvolts for the high gain (28dB) models and 93,000 microvolts for the low gain (19dB) models.

Hmmmm... Using Winegard's own conversion chart from page 26 of the same catalog, that means that their low noise preamps can output about 57dBmV with a FIVE CHANNEL LOAD without developing excessive cross modulation. Does anyone believe that? That's four times the maximum attainable power output per channel of a Channel Master 7775 or 7777, at two and a half times the channel load. Cripes, the Holland Electronics (no relation?) "high powered" rack-mounted UHF strip amplifiers, which I think are now discontinued, could barely develop that kind of output of a single channel.

The HDP-269's 350,000 microvolt maximum input is 51dBmV. With 11 to 12 dB gain, its amplifier output would be 62 or 63 dBmV. My trusty, workhorse Blonder Tongue BIDAs, which regrettably have noise figures of around 8 or 9dB, can develop an output level of just 46dBmV with 60 channel loads. To simply the arithmetic, I'll fudge a little and call that the 64 channel rating: 46dB at 64 channels, 49dBmV @ 32 channels, 52dBmV @ 16 channels, 55dBmV @ 8 channels, 58dBmV @ 4 channels, 61dBmV @ 2 channels, and 64 dBmV @ 1 channel. So why am I paying $400 per amplifier for behemoths with 8-9dB noise figures? In fact, if Winegard is using the same loading assumption for the HDP as it does for its AP's, I might start using them to light Christmas trees.

It would also be very retro if the manufacturers would actually publish meaningful specs.

We should all live so long. But I'm even more concerned about the relevance of the methodology we are using to arbitrarily arrive at useful parameters for estimating amplifier power sufficiency when loaded with digital signals, rather than analog ones.

Wow, I'm getting overloaded(pun intended) with information here.

The info I have for the 91XG was from the AntennasDirect (www.antennasdirect.com/91XG_HDTV_Antenna.html) site which apparently is lacking in useful data. I recall that it was a clone of a Blake model sold in the UK? Not sure which one though.

holl_ands, with your data from above on pre-amp overloads, you first indicate that the Winegard model would be better or did you refine that to say the CM 7775 was the same as the Winegard?

AntAltMike, you mentioned that the 8-bay CM4228 would be a better choice than a Yagi style? I was under the (probably misinformed) impression that Yagis were more directional and that would be better for my situation. I have a 4228 still in the damaged box it came in, would require some straightening but I could probably install in place of the 91XG this weekend. Before I go up there though I'd like to know if a pre-amp swap-out is in the works. I also still have the CM4248 which can be used.

Too bad I can get you all here at my location, my treat! It sounds like my situation could be a challenging one that appears to intrigue or interest you. This stuff definitely interests me but I don't have the knowledge to understand a lot of it.

AntAltMike, you mentioned the RS ATSC tuner, I had one but returned it as it was problematic fitting into the scheme of my whole system. But, I am going to pick it back up as I recall it had a SNR readout meter...which I'm assuming would be of some usefulness..?

All I meant was that I was visualizing the 4228's channel 22/23 sidelobe to be just a little more favorable in terms of rejecting the undesired signal from that angle, because the undesired signal would arrive at each of the 4 bay sub-stacks at a different time, but that is just one selection consideration. I can't say that the 4228 antenna is better for your situation than a 91XG, because yours has more gain, and if you "misaim" it by a few degrees, you probably can achieve the same rejection of the undesired signal.

Right now, you may understand less about your siituation than you did before you entered this thread. Originally, when you had concluded that there must be obstructions between you and Sutro because you got better performance misaiming your antenna, the real reason you got better performance was probably that you were mitigating channel 68/47 signal at the same time. Holl_ands' preference for your situation would be to go with a lower gain preamp. I'd like to get that spreadsheet of his to open before I concurred, because I still suspect that it would develop marginal signal levels of the distant transmitters, and even if a topo program says that solid planet earth is not in your way, its vegetation still might be, and you might desire some additional margin to sustain reception under wet weather conditions. My preference is to have you drop in a 750Mz low pass filter and a UT-2700 notch to weaken 47, but either would likely improve your system performance.

You show A-KRCB as channel 51 but it should be channel 22 so one notch covers both the analog and digital stations. Also the distances and angles to all Keenan's stations can be found here:
http://www.fcc.gov/fcc-bin/tvq?state=&call=&arn=&city=&chan=&cha2=69&type=0&facid=&list=2&dist=100&dlat2=38&mlat2=26&slat2=50&dlon2=122&mlon2=41&slon2=57&size=9

See my Post #93 above for the corrected RevD spread sheet and listed errata.
I also added calculations for the W-G AP-4700 Preamp.

Calculations show that both the AP-4700 and the HDP-269 should keep the strong signals coming
from KRCB (both analog and digital) well below the spec overload point when pointed toward Sutro Tower.

The high gain CM-7777 and CM-7775 (UHF only) is shown to be unsuitable for use in a
urban/suburban environment with broadcast towers in close proximity
(but then most of us knew that to begin with).

A couple of additional notes and questions for you all.

Solid planet earth is definitely in my path. There are a couple of 1000' plus peaks on my line of sight to Sutro.

Using the RS Accurian tuner I get the following readings from their "meter", this is with the antenna orientated for maximum signal strength for KBHK.

KBHK.......SNR-18-19dbs with signal strength at around 66-67

KCRB.......SNR-30-32dbs with signal strength at around the low 90's

KTLN........SNR-15-16dbs with signal strength at around 60

Additional Sutro Tower station,

KRON(ch 4-digital 57) constant picture breakups unwatchable ...SNR about 15-16 and signal strength about 40-60

Mt St Helena,

KFTY(ch 50-digital 54).....SNR-2-15db with signal strength of 9...this station would be behind me so I guess it indicates the antenna is doing a fair job of rejecting signals from the backside.

Whether this info is of any value, I don't know, you guys are the experts. Obviously, the best course of action is to try and see what works better, if anything. I guess I'm looking for answers on whether things like horizontal stacking and such are fundamentally sound. I'm also unsure from the discussion whether a different pre-amp is warranted, again, testing it is probably the best solution. Again, I do appreciate the input and I have learned a whole lot more than I knew before starting this journey, and for that I want to thank everyone.

Now just get me better signal strength and I go away... :D

A couple of additional notes and questions for you all.

Solid planet earth is definitely in my path. There are a couple of 1000' plus peaks on my line of sight to Sutro.

Using the RS Accurian tuner I get the following readings from their "meter", this is with the antenna orientated for maximum signal strength for KBHK.

KBHK.......SNR-18-19dbs with signal strength at around 66-67

KCRB.......SNR-30-32dbs with signal strength at around the low 90's

KTLN........SNR-15-16dbs with signal strength at around 60

Additional Sutro Tower station,

KRON(ch 4-digital 57) constant picture breakups unwatchable ...SNR about 15-16 and signal strength about 40-60

Mt St Helena,

KFTY(ch 50-digital 54).....SNR-2-15db with signal strength of 9...this station would be behind me so I guess it indicates the antenna is doing a fair job of rejecting signals from the backside.

Whether this info is of any value, I don't know, you guys are the experts. Obviously, the best course of action is to try and see what works better, if anything. I guess I'm looking for answers on whether things like horizontal stacking and such are fundamentally sound. I'm also unsure from the discussion whether a different pre-amp is warranted, again, testing it is probably the best solution. Again, I do appreciate the input and I have learned a whole lot more than I knew before starting this journey, and for that I want to thank everyone.

Now just get me better signal strength and I go away... :D
I bought one of those RS tuners because the clearence price of $90 was too low to resist. I am not sure what the SNR number represents but it is not based on the AGC value or channel power for an analog station. The channel power does seem to affect the signal strength level. When I tune to an analog station number (after clearing all channels by doing an auto re-scan with the antenna unconnected) The SNR number is usually an erratic 17 dB regardless of how strong the station is but the bar graph and signal strength readout is a consistant 49% for strong stations. Both those values seem to have more meaning when tuned to a digital station but I don't think you can read RF signal strength using them.
My recomendation for reducing channel overload would be to try a WG-4700 or 8700 pre-amp plus a filter for channel 68 if necessary. If KRCB is a problem even with the WG pre-amp the best solution to eliminate it would be to get another XG-91 and horizontally stack them to place a notch at 30 degrees off the mainlobe peak.

If KRCB is a problem even with the WG pre-amp the best solution to eliminate it would be to get another XG-91 and horizontally stack them to place a notch at 30 degrees off the mainlobe peak.
That's the direction I'll probably take initially, a horizontal stacking and see what happens. I'm having a little trouble wrapping my head around the idea of using a lower gain pre-amp, but that is probably my lack a understanding more than anything so I'll probably get one of the WG pre-amps and try it as well.

You mentioned center to center boom width should be around 22-24"?

What's the best way to join the leads? The antennas have a balun contained in a box attached to the boom so it's a 75ohm coax feed from the antenna.

That's the direction I'll probably take initially, a horizontal stacking and see what happens. I'm having a little trouble wrapping my head around the idea of using a lower gain pre-amp, but that is probably my lack a understanding more than anything so I'll probably get one of the WG pre-amps and try it as well.

You mentioned center to center boom width should be around 22-24"?

What's the best way to join the leads? The antennas have a balun contained in a box attached to the boom so it's a 75ohm coax feed from the antenna.
Use 22.5" unless there is a problem with the antenna elements getting too close.
holl_ands had this post about the best way to combine antennas:
http://www.avsforum.com/avs-vb/showthread.php?p=5768104&highlight=canada#post5768104
Cheap way- same null but insertion loss may cancel much of the gain of using two antennas: CM model 0538 available from:
http://www.warrenelectronics.com/Antennas/joiners.htm
The gain of the pre-amp needs to overcome the losses in the lead-in cable and reduce the effect of the noise factor of the receiver input. The usual rule is 10dB more gain then lead-in loss is sufficient; after that additional gain won't help much and overload from too much gain can make things much worse.

Okay so the Lindsay 2WCU1469 would be the one to use. With a cable run of 100-125' would RG11 be a better choice than RG6?

Would it be a better idea to stack a CM4228 on top of the 91XG and join them?

You're picking the most expensive choice first. Why would you want to try a horizontal stack first? It will cost you several hundred dollars and will not mitigate any overload coming from 47/68 if that turns out to be the problem. You can rule that problem out much more readily and economically either with the filters that I recommend or the preamp that Holl_ands recommends.

If your stack gets you more net gain, stacking will increase the undesired signals from 47 and 68 as well. You can rule out channel 22/23 by putting a $30 Jointenna temporarily on the line. It will crush ABC 24, but it will at least tell you if mitigating 23/24 helps you. If it does, you might then try forming a horizontal null which could slightly weaken 22/23 without weakening 24, but until you establish that is contributing to your reliability problem on 45 and otherwise, I think you would be wasting a lot of time and money by stacking first.

While horizontal stacking can mitigate an off-axis 22/23 Mz undesired signal component, which I doubt it your problem, there is no optimal horizontal spacing to get the two antennas to resonate favorably at all frequencies. If you want to do something really cool, rig up something motorized that will let you vary the horizontal spacing to optimize on each distant channel. That's what I'd do if I didn't have to work for a living.

I used to have this math teacher named Mary Tighe. One day, she saw that I was doing nothing (that could have been any of a number of days) and said, "What are you doing?" I replied, "I'm thinking" She said. "You're not supposed to think. I do the thinking here!"

She was a useful math teacher for most of the other students but not for me.

Keenan is doing to much thinking. He keeps thinking of the most expensive and most difficult to implement solution but he doesn't yet know the problem. He needs to know for sure if he has a preamplifier problem caused by overload, which I doubt. He can definitively resolve that for under a hundred dollars with filters. If he chooses to go with the low gain amplifier, he might as well use RG-11 because, without a real signal meter, he doesn't know if his distant signals will be near the threshold or not. RG-11 will cost him maybe twenty bucks.

LOL, you're right, because I don't understand most of the math and theory regarding antenna usage my first inclination is to throw money at it to fix a problem that I may not even have..

I'll order a JoinTenna model 0585-1 and go from there. I think this was already answered, but can I insert this in the line post pre-amp so I don't have to go up the tree, at least to see if it has an effect?

No. Post- preamp notch attenuation would only "help" your receiver correctly process channel 22.1 if the receiver was previously not able to process it. You're going to have to tough this one out, but again, you are overly relying on your signal strength meter's numerical quality value of channel 22.1. According to the FCC website's transmitter power figures, it is not your strongest station. 47 and 68 are.

Actually, just moving the preamp down will reduce all of the inputs by about three dB. If you are primarily afflicted by an overload problem, you might get somewhat improved performance from doing that before any filters even arrive.

You can accomplish something by temporarily moving the preamp down, but don't move it down any further than you have to. If you make a splice insertion point even twenty feet above the ground and put the preamp there, you can then mix and match with the THREE jointennas (23, 47 and 68) to see which channel, if any is overloading your preamp.

If the problem is 68, leave in the Jointenna. If it is 47, then buy a tuned UT-2700 or even an MWT-U to weaken that without disturbing your 45. If it is 22/23, then you might FIRST try a UT-2700 tuned to the analog visual carrier of 22, because that can be notched without damaging DT-24, but if the problem is DT-23 (which you see as 22.1), there is no notching possible, so then and only then do you try to pull off a minor miracle with the horizontal phase cancellation.

I've seen receivers display 90% to 100% on lots of channels. I never even bother to measure those signal's actual signal strength with a field strength meter because they almost never are causing a problem. With some products, you can have a signal strength of 100%, increase it by a hundred fold (which would make it 10,000%, if the 100% were a measure of actual signal strength referenced to some upper limit), and still not have a problem. And I have bad news for you if you think that increasing the nominal signal quality from, say, 40% to 50% or from 50% to 60% is going to make much difference in the reliability of your problem signals if you do not have line of sight reception from the San Francisco towers...

You're picking the most expensive choice first. Why would you want to try a horizontal stack first? It will cost you several hundred dollars and will not mitigate any overload coming from 47/68 if that turns out to be the problem. You can rule that problem out much more readily and economically either with the filters that I recommend or the preamp that Holl_ands recommends.

If your stack gets you more net gain, stacking will increase the undesired signals from 47 and 68 as well. You can rule out channel 22/23 by putting a $30 Jointenna temporarily on the line. It will crush ABC 24, but it will at least tell you if mitigating 23/24 helps you. If it does, you might then try forming a horizontal null which could slightly weaken 22/23 without weakening 24, but until you establish that is contributing to your reliability problem on 45 and otherwise, I think you would be wasting a lot of time and money by stacking first.

While horizontal stacking can mitigate an off-axis 22/23 Mz undesired signal component, which I doubt it your problem, there is no optimal horizontal spacing to get the two antennas to resonate favorably at all frequencies. If you want to do something really cool, rig up something motorized that will let you vary the horizontal spacing to optimize on each distant channel. That's what I'd do if I didn't have to work for a living.
While the horizontal stack with a low insertion loss combiner is an expensive solution it will improve on-axis performance across the UHF band. You would only need to change the spacing if you needed to move the null. I have modelled a stack of two CM4248s at 22.7 inches. I have enclosed a comparison horizontal beampattern with a single 4248 plotted at 526 megahertz. I agree that Keenan should first try something simple to see if overloading is his problem. I would suggest he just try switching to a WG-4700 or 8700 pre-amp which is much more overload resistant than a CM 7777. I doubt he would overload his receiver with that pre-amp given a long RG-6 lead-in from a tall tree. That seems to me even simpler than messing with filters.

I finally had some time to do a couple quick RADIO MOBILE propagation prediction runs for Keenan location.
My goal is to encourage others to use this FREE and relatively easy to use program, along
with some handy-dandy spread sheets to help understand what is possible with OTA DTV reception.
I'm still collecting data on how much Fade Margin various situations "need".

=====================================================
It confirms that KRCB-DT and A-KRCB are operating uncomfortably close to the spec
overload point for the CM-7777, but depending on how much +/- 28 degree sidelobe
notch depth is truly available against CH22/CH23.
Unfortunately, most antennas don't develop a strong sidelobe notches at the lower frequencies.
[Fortunately, the W-G UT2700 tunable notch can be used, one notch for each channel.]
The high gain of the CM-7777 also may be causing intermods in the HDTV Tuner.
Assuming a 10 dB sidelobe notch, the input to the HDTV would be close to -6 dBm (43 dBmV),
which would generate low level intermod noise products preventing reception of weak stations.

The higher gain W-G AP-4700 (or equal) Preamp is a slightly better choice than the HDP-269,
providing a slightly higher Fade Margin for the desired KBHK-DT from Sutro Towers,
and has a spec overload point that is much higher than the maximum input signal
so that the SFDR (Spurious Free Dynamic Range) can be maximized.

There is a delicate balance between using a higher gain Preamp to overcome the
coax downlead and HDTV Noise Figure Losses vs providing ample "head room" below the spec overload point.
The HDTV Tuner is also likely to be overloaded, so a Variable RF Attenuator should
be inserted prior to the HDTV and tweaked for "best" reception.

==========================================================
For KBHK-DT, RADIO MOBILE shows two hills in the way, the first where the KTLN tower is located
and second on the side of the hill S. of Santa Rosa.
The two knife edge diffraction path causes 52 dB loss over and above the Line-Of-Sight path (that's a lot!!!)
The received signal level was calculated to be about -77.1 dBm (or -28.4 dBmV) for the XG-91 feeding a Preamp.
RADIO MOBILE calculated a Fade Margin of 15.5 dB, but there are a bunch of parameters
not included in the results, resulting in a very minimal 8 dB after making adjustments.

I use one and only one parameter calculated by RADIO MOBILE: Total "Path Loss".
It is calculated using the unit locations, the terrain database, the transmitted frequency
and not much else. The "Path Loss" is independent of any assumption re TX ERP, TX/RX
Antenna Gain and various other parameters that can be entered into the program.
Path Loss is then plugged into the DTV FADE MARGIN CALC spread sheet, which incorporates
all of the site specific parameters (as best as I understand them, so tweak away).

KTLN (CH47 and 68) signals originate on the back side of a directional tower antenna
and then diffract off the side of the "hill" South of Santa Rosa, resulting in a Diffraction Loss
of about 40 dB in excess of Line-Of-Sight.
The receive signal levels were calculated to be within a few dB of KBHK-DT,
which isn't strong enough to be interfering with KBHK-DT reception.
Hence the CH47 Join-Tenna isn't attacking the real problem (CH22/CH23).

More antenna gain could help, such as Horizontal Stacking, but only yields 2-3 dB gain.
Of more importance would be the "space diversity" effect of having different parts of
the antenna
separated so that a multipath null in one part of the array doesn't affect a different part of the array.
This is the primary reason the CM-4228 has been shown to be such a high performer.

A Horizontal Array also can develop a very deep notch that can be directed towards CH22/CH23,
but if the Preamp is chosen to operate in the linear region to begin with,
this may not be needed.

See attachment for path profile and calculation files.

Please let me know if you find any problems, there are a lot of meticulous details.
No, I'm not volunteering to do entire SF area. I've already done LA and San Diego.

Unfortunately, I can't get Holl_ands's two most recent links to open either, and when I try the "right click" workaround that works for him, it gets me a different, insurmountable, "no can do" message.

Has a link been furnished to this free, Radio Mobile program? And why is it free? 100,000 Watts is no longer free, and the free, NIA calculator is gone, too.

Since Keenan's nearby hill takes the possibility of overload by 47/68 out of the picture, he is basically left with two problems: too much local 22/23 signal, and insufficient or qualitatively inadequate, distant 45, 24, etc.

I'd be interested in seeing some of the assumptions Holl_ands is using. Is 23 up to its licensed power level or still running at its temporary authority? For the thermal noise floor, I have always assumed that since the figure I used for analog estimates was between -59 and -60dBmV, and since I thought that was based on the entire 6Mz bandwidth, and since the DTV tuner industry would like us to use dBm instead, I have been assuming that the noise floor is about -108dBm. Is that about what the industry is using for a reference level?

It has been posted elsewhere that there is some kind of mandated or engineered need for a 15.6 or 15.9 dB S/N ratio to be seen at the "tuner". Two thoughts: first, must one add the tuner's noise figure to that, meaning that the minimum input level would be about -82 to -83dBm if the tuner had about a ten dB noise figure?

Second: are the tuners engineered to process signals at anemic input levels? Consider DBS I.F. signal processing parameters. The DBS I.F. frequencies are just above UHF (950Mz to 1,450Mz) frequencies. Since the bandwidth is about 30Mz, then the measured noise floor would be about five times greater than a 6Mz noise floor, or -103 dBm.

Supposedly, the DBS, QPSK signals can be processed if their S/N ratio is as low as 8dB. But the DBS tuner manufacturers say that their tuners need a minimum input of -60dBm, and when Sonora Design bench tested a bunch of early Sony receivers, it saw that performance started to deteriorate when the input signals dropped below -66dBm. Yet, assuming a -103dBm noise floor and tuner noise of 10dB, the tuner noise should have been inconsequential. But when you take a DBS signal that has dropped to, say, -75dBm to -80dBm and boost it with a "dime store" inline 20dB amp, the signal gets recovered to a processable level. That has led me to conclude that determining tuner input sufficiency requires more than maintaining the minimal S/N ratio.

I've only seen one published figure for minimum input level by one manufacturer, and it was either -80dMb or -85dBm (I'm getting senile, too!). If anyone here has seen any published threshold input specs, I'd like to see them. In fact, published, manufacturer's info for DTV tuners is so sparse that it might be worth creating a sticky post where we could store it, if there is even enough info available to warrant such a post (I think Drake and PDI are the only two manufacturers in whose literature I have ever seen processor noise figures: 9dB and 10dB).

Preserving "headroom" is going to become a much more important consideration in establishing the integrity of off-air amplification systems than it ever was with with cable or even broadcast analog for a number of reasons.

With cable TV, all signals are at the same level, so any "wideband" noise affects all channels similarly, whereas in an off-air system, noise and intermodulation products that would have no effect on equal strength signals would decimate the weaker ones. Thus, the notion of arbitrary levels at which amplifiers "overload" will be much less useful than it was previously.

The byproducts themselves will be wider, since before, all we cared about was the simple interactions between two or three visual carriers, and whether they fell on or very near to another visual carrier, but now, we have these 6Mz wide signals interacting, and they may adversely affect the weak, desired DTV signal regardless of where, within the channel band, they land on it.

Given that the broadcast bandwidth has been reduced from 68 channels to 50, and in most markets, it has been effectively reduced to 45 since very few VHF lowband stations will be reverting to lowband, we are going to be dealing with a lot more adjacent channel problems.

I surmise that Keenan may have ABC DTV available through other means, like cable TV or satellite, so that 24-D from San Francisco is not essential, but other people will not be so lucky. Most of my customers are in Washington, DC and are within a few miles of ABC-D on 39 and WB-D on 51. Baltimore is presently using 38 for CBS-D, and 40 for WB-D and 52 for ABC-D. Most of my customers are within five miles of the Washington towers but those towers are about thirty to thirty five miles from the Baltimore towers. Because my customers basically encircle the Washington transmitters, I can have two headends just a few miles apart where, from one building, adjacent channel digital transmitters are directly inline, with one being five miles away and the other thirty-five miles away, but, five miles to the east, from another headend, the transmitters form a ninety degree angle to one another.

FWIW, strong DTV channel 39 adversely affects weaker, lower adjacent DTV channel 38 more than it does weaker, upper, adjacent channel 40. I don't know if that is because the DTV signal has a pilot carrier that is just .9Mz above the lower band edge that makes the differential between the it and the adjacent lower channel greater or if I have just been unlucky for some other reason.

Anyway, I can usually get the weak, adjacent upper channel to be processed if the differential between it and the stronger, adjacent channel below it is less than about fifteen dB, but don't take those numbers to the bank, because they are based on an inadequate sample and imprecise observations and recollections.

Assuming 10dB off axis rejection, what does Holl_ands estimate the differential between local 23-D and distant 24-D to be? The 22 analog carrier can be squashed with a tunable notch without affecting 24, but nothing that convenient can be done to 23-D without injuring 24-D.

If someone in Keenan's locale needed 24-D, like I might if I was servicing a multiple dwelling unit there, they could point a second antenna directly at 24-D, bandpass filter it, and couple it with their main antenna coax to effectively phase cancel the undesired signals. Funny thing though. If one aimed a horizontal stack at San Francisco to take advantage of the "space diversity" effect that Holl_ands alluded to in the previous post (an underappreciated characteristic of multiple bay antennas that explains why they consistently outperform Yagis in attics), then I don't think the phase canceling would work well because the undesired signal components from the two stacks could not both be kept in phase with one another. It could be developed, but not at the top of a 70 foot mast or tower. On a flat roof, I could put one antenna on a 3' x 3' non-penetrating frame with no ballast, and slide it "side to side" until I saw the most favorable spectrum form on my analyzer, as I actually had to do once for a 550 unit condo, but again, such extreme remedies are not for the do-it-yourselfer.

The "space diversity" effect that Holl_ands alluded to in the previous post is an underappreciated characteristic of multiple bay antennas that explains why they consistently outperform Yagis in attics.

Has a link been furnished to this free, Radio Mobile program? And why is it free? 100,000 Watts is no longer free, and the free, NIA calculator is gone, too.


When I googled radiomobile this is the first link I got:
http://www.cplus.org/rmw/english1.html
It is free for the same reason that Linux and much other quality software is free- the author chose to release it that way. It is also based on path loss work and elevation data that have already been paid for through US tax dollars. I have used radiomobile and it is a great tool for calculating path loss. The only remaining path loss question is the effect of items very close to the receive antenna like trees and buildings etc. The program can also calculate signal strength margins but they were designed for mobile radio applications and it can be easier to just use a spreadsheet to finish the calculations. Anyone that is interested will find a good deal of relevant info at the sites that holl_ands has posted.

Here's the link for Radio Mobile,

http://www.cplus.org/rmw/english1.html
Radio Mobile WEB Site

<edit> I see that deconvolver has already posted the link. It involves DL'ing about 5-6 files but it works, not that I know how to use it...

If you like, PM me with your email address and I can send you the unzipped files that you can't download.



holl_ands, there is some wonderful work here, thank you. There's references to many things I don't understand but your note sections gives me the gist of what I believe I need to know. I have always felt that the hill that is in close proximity to me has been the biggest impediment to quality SF reception. Just west of me about 4-6 miles there's a forum member here in Santa Rosa that has been getting most of the stations from SF and even the KNTV signal from Loma Prieta, clear down in the south bay past San Jose, with a CM4228 in his attic!! Of course, he doesn't have the hill to deal with.

I'd be interested in seeing some of the assumptions Holl_ands is using. Is 23 up to its licensed power level or still running at its temporary authority? For the thermal noise floor, I have always assumed that since the figure I used for analog estimates was between -59 and -60dBmV, and since I thought that was based on the entire 6Mz bandwidth, and since the DTV tuner industry would like us to use dBm instead, I have been assuming that the noise floor is about -108dBm. Is that about what the industry is using for a reference level?

It has been posted elsewhere that there is some kind of mandated or engineered need for a 15.6 or 15.9 dB S/N ratio to be seen at the "tuner". Two thoughts: first, must one add the tuner's noise figure to that, meaning that the minimum input level would be about -82 to -83dBm if the tuner had about a ten dB noise figure?

Second: are the tuners engineered to process signals at anemic input levels? Consider DBS I.F. signal processing parameters. The DBS I.F. frequencies are just above UHF (950Mz to 1,450Mz) frequencies. Since the bandwidth is about 30Mz, then the measured noise floor would be about five times greater than a 6Mz noise floor, or -103 dBm.

As I mentioned before, holl_ands has posted a good deal of info over at the hdtv.forsandiego.com site. You will find most of the answers to what he is doing there. Here is a link to a spreadsheet he created for calculating fade margin (I didn't look to se if he has posted a more recent version):
http://hdtv.forsandiego.com/messages/1/DTV_Fade_Margin_Calc_Example-3108.xls

I posted the Santa Rosa files on the fol thread, which includes info on RADIO MOBILE:
http://hdtv.forsandiego.com/messages/1/2846.html?1126976722

=======================================================
PS: Thanks AntAltMike for pointing out the footnote in the Winegard Catalog.
[I KNEW I had seen something somewhere on W-G overload....]

It's also in the 2002 edition. But not on the W-G or retailer websites.
Maybe because the wording is so quirky:

"Outputs stated for 7 VHF and 5 UHF channels at -46 dB cross modulation"
Where what is "stated" in their table is the "Maximum Total Input# (Microvolts)".

Since the table shows input overloads vs output, perhaps the fol is more accurate:
"Maximum input levels are for 7 VHF and 5 UHF equal strength channels,
resulting in cross modulation products 46 dB below the Output signal levels."

======================================================
So the high overload (AP-4700 or equal) Preamps have a 93,000 uV maximum UHF input.
That is 20 log (93,000) = 99.4 dBuV or 39.4 dBmV or -9.4 dBm (for 75 ohm load).
With a gain of 19 dB, the max output level would be +9.6 dBm (58.4 dBmV).
The output intermod noise floor would be -36.4 dBm (12.4 dBmV ).
To provide the ATSC minimum SNR of 15.5 dB, the weakest output signal would need to
be at least -20.9 dBm (27.9 dBmV), corresponding to an input of -39.9 dBm (8.9 dBmV).

The thermal noise floor is about -106 dBm, hence the minimum detectable ATSC signal
is (-106 +15.5 + Cascade Noise Figure). With 100 feet of RG-6, that's about -85.8 dBm
if a pesky intermod product isn't sitting on the desired channel.
So the intermod products can limit the sensitivity to only -39.9 dBm.
If we had a Preamp with a 10 dB higher overload point, the intermod products could be
expected to be reduced by perhaps as much as 30 dB, for a sensitivity of -70 dBm.

========================================================
References explaining this 3:1 intermod reduction were cited in my Post #60 on 9/9/05.
You want to operate well below the spec overload point in order to maximize
the SFDR (Spurious Free Dynamic Range).
If the maximum signal levels can be reduced by 3 dB, the intermod products are reduced
by 9 dB.
Similiarly, if a Preamp with a 10 dB higher overload point is used, the intermod products
can be expected to be reduced perhaps 30 dB for the same input signal levels.

=====================================================
The CM-7777 has a specified maximum OUTPUT level of 51 dBmV or +2.3 dBm
for 2 input channels, with cross-modulation levels 46 dB lower.
Derating is 5 dB for 4 and 8 dB for 8 (equal strength) channels.
So compare the CM-7777's 4 channel derated max input level of -23.8 dBm
to the W-G AP-4700 5 channel max input level of -9.4 dBm, where both state
a 46 dB (0.5%) cross-modulation output level.

Of course, all of this presumes that the manufacturer specs mean what they say.

==================================================
To convert between microvolts and various dB units:
dBuV = 20 log (uV)
dBmV = dBuV - 60 = 20 log (uV) - 60
dBm = dBuV - 48.75 - 60
dBm = dBmV - 48.75

As I mentioned before, holl_ands has posted a good deal of info over at the hdtv.forsandiego.com site. You will find most of the answers to what he is doing there. Here is a link to a spreadsheet he created for calculating fade margin (I didn't look to se if he has posted a more recent version):
http://hdtv.forsandiego.com/messages/1/DTV_Fade_Margin_Calc_Example-3108.xls

Yes, I posted an updated REVC version.
The Broadcast Antenna Polar Field Plot needed to be converted from relative volts/m to a dB level.
The correction uses 20 log () vice 10 log (), cuz it's volts not power.

========================================================
AntAltMike: In the cited hdtv.forsandiego.com thread above, you'll also find spread sheets
summarizing important specs/measurements for Antennas, Baluns, Preamps, Cable and ATSC Tuners.

And I woud appreciate any additions....

Some thoughts for the future (improvements are "just over the horizon"...so to speak...)

Performance of so-called 5th Generation ATSC Receivers has been discussed
in fol thread. Look for post dates cited below:
http://www.avsforum.com/avs-vb/showthread.php?p=6085224#post6085224

8/16, 8/17/05 et. al. posts have links to lab and on-air tests conducted by CRC (Canadian Research Center)
on the Zenith/LG 5th Gen Prototype Receiver and the Linx (now Micronas) ATSC Receiver.
It actually measures the sensitivity and overload levels, the minimum required SNR and the
additional SNR required for the worst multipath test cases thus far encountered.

7/5/05 post has discussion and links re. European DVB-T Diversity Receivers,
showing how they nearly eliminate signal dropouts.
They have been available for NTSC analog TV reception in automobiles for years.
My '98 Volvo Station Wagon came with a killer Dual Diversity Antenna for FM that
runs circles around my friends earlier Nissan 300Z Diversity FM system.
Maximum Ratio Diversity Combiners are standard for many mobile microphone packs.
And it's in most any Wireless Router that has two or more antenna stubs on it.
SO WHERE ARE THE ATSC DIVERSITY RECEIVERS??????
I've seen various reports re development and field test, but still nothing you can buy.

6/30, 7/15 and 8/3/05 has discussion and my evaluation of the one and only Smart Antenna
system that can automatically maximize desired signal direction and (if they do it right)
has the potential to steer nulls towards undesired directions.
It also has automatic control of the Preamp's AGC level to avoid overload.
A worthy DIY project would be to adapt the Preamp/Combiner Module for 2 or 4 large
external antennas, cuz the DTA-5000 only provides 0-3 dB antenna gain.
It should be capable of outperforming the Lindsay antenna coupler for about the same price, plus of course a CEA/EIA-909 capable STB (e.g Sylvania 6900DTE).

========================================================
Fol. thread has a discussion re advantages of COFDM vs ATSC waveform:
http://hdtv.forsandiego.com/messages/76/2920.html#POST19348
COFDM is used elsewhere in the world for DTT, in the U.S. for Cellphones and
is expected to be used for DVB-H mobile video in the U.S. and will be used to
provide a variety of services on CH52 and above when they are cleared for Home Security
and other uses. Such as Qualcomm's nation-wide CH55 MediaFLO system.

Big advantages are 1) support for SFN (Single Frequency Networks) wherein multiple transmitters carry the same signal
and 2) relatively simple to build Diversity Receivers which provide very significant protection against signal dropouts due to multipath fading.

The ATSC equivalent of SFN may cause multipath problems for all but the newest ATSC Receivers, depending of course on topography.
But if they finally get it to work, networks of repeaters could be used to fill in the terrain gaps that severely limit ATSC reception today.

I have seen several reports re Diversity Receivers for ATSC, but so far nothing is available for purchase.
With the market for stand-alone STB's being surplanted by integrated HDTVs (and expanding HD on SAT/CATV),
and the cost expected to plumet to $50-75, I have to wonder why the STB and chip manufacturers
don't provide a hi-end OTA STB that has Diversity Receivers and Smart Antenna control.

7/19/05 post in the above thread provided links to laboratory and on-air comparison tests for ATSC vs DVB-T vs ISDB-T.
Performance parameters were measured for several different (unindentified) ATSC Receivers, although they are a bit outdated now.

Bon Appetite!!!

re. BACKSCATTER signal path......and ATSC Diversity Receiver references.

A few dozen posts ago, I mentioned BACKSCATTER as being one way that a signal can bounce off nearby objects,
back into the beam of your antenna, even though the source of the transmissions might be on the back side of the antenna gain pattern.
For the same reason a mirror reflects the most light back towards the light source,
the worst Backscatter sources originate from the back side of the antenna pattern,
and will be scattered back towards the highest gain portion of the antenna pattern.
Depending on geometry, sidescatter can also be a problem, esp for those directions where the antenna has significant sidelobe response.

A measurement of the backscatter and sidescatter levels can be found by looking at the relative strengths
of the received multipath signals for a given DTV channel.
[Unfortunately, STBs only display this information to the Design Engineers.]

======================================================
Refs. [a] and [b] below give some insight on this process.
Our buddies at the Canadian Research Center, the Canadian government's technical experts on ATSC and COFDM,
conducted some signal level surveys in various locations, including the described survey around Ottawa.
The ATSC (and COFDM) waveforms transmit a known pseudorandom sequence of bits (PN-511) for 47.48 usec every 24.2 msec.
The ATSC Receiver uses this known data sequence to initialize the equalizer by minimizing
the mean square error between the received sequence and the known PN-511 sequence.
The equalizer tap settings can be observed to log the multipath strength vs delay.

And once the multipath delay is known, it can be used to find the path difference between the direct and reflected path,
using the time it takes light to travel one mile: 5.376 usec/mile.

They found that for a large number of suburban locations, the strongest multipath signals arrived within about 0.2 usec,
which is a path difference of only a couple hundred feet.
That means that your neighbors (and perhaps your interior/attic) are the strongest contributors to multipath.
(Especially your neighbor's two story house with the wire mesh stucco, Al. foil back insulation, Al. gutters, electrical wiring, etc.)

How strong? Roughly equal strength down to 10 dB below the direct path.

On the average, the multipath reflections were insignificant (20 dB below the direct path) for multipath delays
in excess of about 5 to 10 usec, which is a path differential of 1 to 2 miles.

Urban multipath delays were about twice those in surburbia.
So how much multipath should an STB accomodate?
About +/- 20 usec ought to do the job unless there is a tall skyscraper more than a few miles away from you.
So most people shouldn't expect the Zenith/LG 5th Gen chip to work miracles.
Indeed, the Linx/Micronas chip had much better performance for the 0 dB Echo test cases,
including Brazil ensembles, such as might occur for indoor and attic locations.

Of course, there were some infrequent excursions well beyond the "average".
ATSC A/74, "ATSC Recommended Practice: Receiver Performance Guidelines", 18 June 2004,
contains several dozen of these "exceptions" for test purposes.

(So why is it that this information is never collected and released from U.S firms???)

========================================================
References re ATSC Diversity Receivers:

a. "UHF Wideband Mobile Channel Measurements and Characterization using ATSC Signals with Diversity Antennas", Semmar et. al., May 2004:
http://lrts.gel.ulaval.ca/publications/uploadPDF/publication_11.pdf

b. "UHF DTV Band Channel Characterization for Mobile Reception", Semmar et. al.,
Canadian Conference on Electrical and Computer Engineering, Vol.3, pp 1339-1342, 2-5 May 2004.

c. "ATSC Digital TV Receiver using Spatial Diversity Technique", Ju-Yeun Kim, et. al.,
IEEE Vehicle Technology Conference, Sep 2004.

d. "Antenna Diversity for Improved Indoor Reception of US Digital Terrestrial Television Receivers",
Meehan, IEEE Trans on Consumer Electronics, Vol. 48, No 4, Nov 2002.

e. "Joint VSB Terrestrial Digital TV Indoor Reception Project", Wetmore, Schnelle, Meehan, et. al.,
IEEE Trans on Broadcasting, Vol 48, No. 4, Dec 2000.

Guys:

I just bought a new sharp tv with built-in hd tuner and having issues picking up digital channels. Can someone please give me some suggestions? I just created a thread: http://www.avsforum.com/avs-vb/showthread.php?t=584715

I would appreciate your help....

A PDF file of the Winegard series of pre-amps is attached to this post. Levels in dBmV have been added and the reference to the number of stations in allowable input levels.

keenan, There have been several good suggestions made in this thread to help with your DTV reception. How many will work - none, some, or all? IMO, only after an analysis is made using a spectrum analyzer can you determine your next step. You need to read the DTV Reception (http://www.avsforum.com/avs-vb/showthread.php?p=6143315&&#post6143315) section of my post and the two articles by Peter Putnam, links have been provided. These articles are technical but I think you will find them worthwhile. Antennas (http://www.avsforum.com/avs-vb/showthread.php?p=5965016&&#post5965016) at my place of employment are referenced at this AVS post.

holl_ands, How did you derive the levels needed to overload a pre-amp (i.e., direct addition, RMS, etc.)? I assume you know that if a DTV station and a analog station have the same peak value a DTV station will have 11.2 dB more power in the 6MHz than the analog counterpart. That is one reason why I chose to use the Winegard AP-4700. I measured a 10 dB gain for channel 52 after installing the AP-4700. Putnam has a short dissertation (referenced above) on this subject.

0 dBDTV is in the process of being defined by the IEEE (the DTV is superscript but I am not allowed to do HTML tags).

Edited 9-21-05 to change 12.3 to 11.2 dB.
.

A PDF file of the Winegard series of pre-amps is attached to this post. Levels in dBmV have been added and the reference to the number of stations in allowable input levels.

keenan, There have been several good suggestions made in this thread to help with your DTV reception. How many will work - none, some, or all? IMO, only after an analysis is made using a spectrum analyzer can you determine your next step. You need to read the DTV Reception (http://www.avsforum.com/avs-vb/showthread.php?p=6143315&&#post6143315) section of my post and the two articles by Peter Putnam, links have been provided. These articles are technical but I think you will find them worthwhile. Antennas (http://www.avsforum.com/avs-vb/showthread.php?p=5965016&&#post5965016) at my place of employment are referenced at this AVS post.


Yes there has been some great feedback. I'm currently trying to track down someone who can do exactly that, test with the spectrum analyzer, (inexpensively as possible).

It may be a few weeks or more before I have any results to relay here, but I will post them as I am much appreciative for all the help.

A PDF file of the Winegard series of pre-amps is attached to this post. Levels in dBmV have been added and the reference to the number of stations in allowable input levels.

keenan, There have been several good suggestions made in this thread to help with your DTV reception. How many will work - none, some, or all? IMO, only after an analysis is made using a spectrum analyzer can you determine your next step. You need to read the DTV Reception (http://www.avsforum.com/avs-vb/showthread.php?p=6143315&&#post6143315) section of my post and the two articles by Peter Putnam, links have been provided. These articles are technical but I think you will find them worthwhile. Antennas (http://www.avsforum.com/avs-vb/showthread.php?p=5965016&&#post5965016) at my place of employment are referenced at this AVS post.

holl_ands, How did you derive the levels needed to overload a pre-amp (i.e., direct addition, RMS, etc.)? I assume you know that if a DTV station and a analog station have the same peak value a DTV station will have 12.3 dB more power in the 6MHz than the analog counterpart.
.

It's hard to compare apples and pineapples.
I find DTV average power levels to be easy to measure and easy to handle from a theoretical point of view.
But NTSC is anything but simple. Most of the energy is contained in the video sync pulse and then the FM audio carrier, after which there is the chromiance carrier and oh-by-the-way the actual (negative?) video signals buried in there somewhere.
So I would be curious as to how you would define the 12.3 dB difference.
Hmm, you're probably refering to an NTSC vs 8-VSB comparison in the early ATSC documents....which includes the modulation/coding performance gains of ATSC.

========================================================
Since the Preamp manufacturers haven't updated their specs to reflect DTV signals, I had to make a few assumptions.

Overload of an amplifier, whether it is an audio amp, an HF Transmitter or a TV Transmitter is primarily due to PEAK signal excursions.
The peaks get clipped, resulting in distortion. So we need to worry about how often the individual signal voltages sum together and get clipped.

If you were to feed 400 Hz and 1000 Hz sine waves into an audio amp, clipping would occur when the maximum amplitudes of the two sine waves are in-phase so that the sum of their instantaneous voltage values exceeds the maximum voltage capability of the amplifier.

Recall that NTSC signals have always been measured with a video carrier peak power reading meter, since most of the energy is contained in the sync pulses.
And DTV signals are always measured with average power reading meters.
For example, these are the values that are used by the FCC and ATSC when defining ERP and adjacent channel interference requirements.

In order to treat DTV signals equally to NTSC signals with respect to overload specs,
I converted the average DTV signal levels into a peak signal level by adding the Peak-to-Average Ratio for 8-VSB signals.

One measurement of 8-VSB Peak-to-Average levels was done as part of the Australian Test effort in 1997:
http://happy.emu.id.au/lab/rep/
Since DTV peaks are statistical in nature, it is necessary to define how often a certain Peak-to-Average Ratio will be exceeded.
Automatic measuring equipment can determine this ratio for several different confidence levels (actually the fraction of time peak excursions exceeded this level).
Looking at the AUS chart, I extrapolated the curve to about 7.5+ dB and rounded it up to 8 dB, since that would represent a very long time between clipping events.
Note that the most strigent criterion measured was 7.3 dB, exceeded 0.01 percent of the time, where 0.2 dB was contributed by an adjacent channel transmit combiner system.

If you look at some of the early Zenith literature, you will see 6.3 dB stipulated for the 8-VSB Peak-to-Average Ratio.
But this is with very early equipment, perhaps before automatic test equipment and would be representative of a level that is exceeded perhaps 0.1 percent of the time per the AUS curves.

I also see some people, like Dr O. Bendov at Dielectric, rounding it down to 7 dB. So I think we are all in the same ballpark.
These measurements would no doubt also depend on the overload characteristics of the particular transmitter measured.

...
If you were to feed 400 Hz and 1000 Hz sine waves into an audio amp, clipping would occur when the maximum amplitudes of the two sine waves are in-phase so that the sum of their instantaneous voltage values exceeds the maximum voltage capability of the amplifier.
...

Recall that NTSC signals have always been measured with a video carrier peak power reading meter, since most of the energy is contained in the sync pulses.
And DTV signals are always measured with average power reading meters.
For example, these are the values that are used by the FCC and ATSC when defining ERP and adjacent channel interference requirements.

In order to treat DTV signals equally to NTSC signals with respect to overload specs,
I converted the average DTV signal levels into a peak signal level by adding the Peak-to-Average Ratio for 8-VSB signals.

One measurement of 8-VSB Peak-to-Average levels was done as part of the Australian Test effort in 1997:
http://happy.emu.id.au/lab/rep/
Since DTV peaks are statistical in nature, it is necessary to define how often a certain Peak-to-Average Ratio will be exceeded.
Automatic measuring equipment can determine this ratio for several different confidence levels (actually the fraction of time peak excursions exceeded this level).
Looking at the AUS chart, I extrapolated the curve to about 7.5+ dB and rounded it up to 8 dB, since that would represent a very long time between clipping events.
Note that the most strigent criterion measured was 7.3 dB, exceeded 0.01 percent of the time, where 0.2 dB was contributed by an adjacent channel transmit combiner system.

If you look at some of the early Zenith literature, you will see 6.3 dB stipulated for the 8-VSB Peak-to-Average Ratio.
But this is with very early equipment, perhaps before automatic test equipment and would be representative of a level that is exceeded perhaps 0.1 percent of the time per the AUS curves.

I also see some people, like Dr O. Bendov at Dielectric, rounding it down to 7 dB. So I think we are all in the same ballpark.
These measurements would no doubt also depend on the overload characteristics of the particular transmitter measured.
I think that you should really consider the statistics of adding multiple DTV signals more carefully. If you use a peak to average ratio exceeded .01% of the time in a single channel but then add the voltage levels to determine the limit for two simultaneous channels the peak level calculated would only be exceeded about 1x10^-8 of the time. If the signals were independant and Gaussian (they're not Gaussian) then the proper addition for a constant probability of exceeding the threshhold level would be to perform a power sum not a linear voltage sum. I expect that for a large number of channels with similar levels as in a cable TV system the power sum would be a better way to estimate clipping performance with digital signals than a voltage sum would be. The voltage sum would be correct for NTSC signals or a mix of one ATSC and one NTSC signal though.

1. The Peak-to-Average statistics I described above were for a single DTV channel.
Since we would want to keep the mean time between clipping events fairly low, we would want to operate the Preamp
so that the average signal level was at least 8 dB below the peak clipping level.

2. For the case of two (or more) equal strength DTV signals, joint statistics, such as what you describe would apply.
For two DTV signals, I would expect only a fairly small 3+ dB back-off relative to the single DTV signal case,
since adding another DTV signal only adds very infrequent events when the two peak signals coincide.
It is effectively as if you had only one DTV channel with twice the average "noise" energy
and approximately the same underlying statistics (gaussian + gaussian = gaussian).
BUT, the ATSC pilot signal carries more energy than the gaussian noise part, complicating any simple analysis.

3. For multiple DTV signals, the backoffs are probably in the same ballpark as are currently listed by C-M and W-G for NTSC signals.

4. For the case of one DTV and one NTSC strong signal (e.g. the Santa Rosa situation),
the duty cycle of the NTSC sync signals must be convolved with the statistics of the DTV signal.
But with the NTSC sync duty cycle being so high to begin with, my first cut was to simply add the NTSC peak power
to the DTV average power plus the DTV Peak-to-Average Ratio, as was done in the overload calculation spread sheet.

5. For the case of multiple strong DTV and NTSC signals, the duty cycles of the various NTSC signals
would need to be convolved to derive an underlying NTSC clipping probability that would then need to be convolved
with the DTV clipping probabilities. Hmmmm, could get messy...

And how close would the NTSC sync signals from different stations on the same mountain top be synchronized upon arrival?
Aren't they all synchronized to WWV? And to what accuracy?

And if they aren't perfectly synchronized, then there would be long periods
of time during which they would be, followed by even longer periods of time when they would not overlap,
before repeating the long period of time when they do overlap and result in the most clipping....
Sounds like a worst case analysis is in order, in which the NTSC peak power levels are presumed to coincide a large percentage of the time.

6. Most real world situations have multiple NTSC and DTV signals, but they vary several dB from transmitter to transmitter
and invariably are going to vary even more by the time they arrive at the receiver, due to differences in path loss
at different frequencies, antenna gain variances and most importantly antenna location within the varying multipath signal strength "stripes".

=====================================================
The recent on-air antenna test results posted by Bob Chase shows the relative NTSC and DTV spectral signal levels at his location.

Note that since the Santa Rosa interference sources were adjacent channels from the same tower,
the relative power levels are probably similiar to those found for fol. Houston stations:
KUHT (N08+D09), KTXH (D19+N20), KRIV (N26+D27) and Bob's own KHWB (D38+N39).

======================================================
Wouldn't it be easier if someone would simply make some measurements (in-lab and ON-AIR) using REAL Preamps????

Question for Bob Chase:
In your signal spectra charts, KUHT-TV (N08) had an unusual hump between 180 MHz and
the visual carrier at 181 MHz.

I see that this PBS station does datacasting, which presumably uses 8-VSB packets,
and hence would not cause this hump.

I wondered if you knew whether they might also be using something like the DotCast dNTSC datacasting system
(also used for MovieBeam) that adds a reduced level QAM carrier in quadrature onto the visual carrier?

So I would be curious as to how you would define the 12.3 dB difference.
First, the 12.3 dB should have been 11.2 dB and was corrected above.

With a spectrum analyzer set to 300 KHz RBW. Measured the span for a DTV channel, them measured a NTSC channel (the aural FM carrier was NOT included). The DTV was about 3.7 times the width of the NTSC visual. 20 Log3.7 = 11.2 dB. Also created a 50% duty cycle pulse with a DC level of 1V (2V P-P), then set the duty cycle to 14% (50/3.7) which produced .28V DC level. 20 Log(1/.28) = 11.1 dB.

There is a good article by John D. Freberg, Understanding DTV Transmission Measurements (http://broadcastengineering.com/mag/broadcasting_understanding_dtv_transmission) in Broadcast Engineering on this subject.

Overload of an amplifier, whether it is an audio amp, an HF Transmitter or a TV Transmitter is primarily due to PEAK signal excursions. The peaks get clipped, resulting in distortion. So we need to worry about how often the individual signal voltages sum together and get clipped. If you were to feed 400 Hz and 1000 Hz sine waves into an audio amp, clipping would occur when the maximum amplitudes of the two sine waves are in-phase so that the sum of their instantaneous voltage values exceeds the maximum voltage capability of the amplifier.
Yes, I am well aware. That is one of the reasons that I Tri-Amped my main speaker system more than 25 years ago (recently redone and Bi-Amped).

Another request for someone to help me out with below..

Guys:

I just bought a new sharp tv with built-in hd tuner and having issues picking up digital channels. Can someone please give me some suggestions? I just created a thread: http://www.avsforum.com/avs-vb/showthread.php?t=584715

I would appreciate your help....

Don't even get me started on speakers.....I'm in the middle of a rebuild.

When I'm done, I should be able to sell the antique parts on eBay for
about what I paid for the speakers back in 1971.
Not bad, zero cost of ownership, ignoring inflation.

My 24 year old Altec's were biamp'ed not long after I bought them...notable difference.
Today, the 15-inchers are recycled as a sub-woofer pair fed by a 1/3-octave equalizer
to ensure flat response down to below 30 Hz. [BTW: they came as a "QB3" Thiel/Small alignment.]

L/R are DIY planar magnetic dipoles plus ribbon tweeters and a separate amp feeding 10-inchers.
Originally I planned to replace the Altec's 800 Hz Sectoral Horn, using 7-inch instead of 10-inchers.
But I liked the bi-amped dipoles so much, I only built the Center in that configuration.

I'm still using LR/RR bass reflex cabinets I built in mid-70's for Quad after reading AES Journal
re Thiel/Small speaker alignments, although the 6.5-inch speakers have been replaced....twice.
One of these days I need to finish building new LR/RR cabinets, but I'm still
vacillating on whether these should be dipoles, and if so,
how is THAT going to work given the asymetrical nature of that part of the room.

====================================================
I've seen and heard some outrageous speaker systems at CES, including triple amp'ed surround speakers.
(That's 15 amplifiers, plus sub-woofers, so watch yur wallet.)

But the improved imaging of the dipoles grab me every time.
Unfortunately, the only systems that sound better than my antiques tend to be
outrageously expensive electrostatics or almost affordable planar magnetics.

PS: The Planar Magnetics I use are the B-G units from partsexpress.com, the same as
are used in the new Martin-Logan ATF speakers (e.g. Mosaic & Montage).

Based on my research, I found that the Zenith Silver sensor is a highly recommended indoor antenna. However, I read the description on their website, though, they seem to be marketing this to the urban crowd. I'm in a rural area about 20-30 miles from the broadcaster.
Would this be a good purchase for me? Or should I consider something else? I do not have any buildings nearby. Just a few houses and a bunch of trees.

If you can install a 4-Bay Bowtie antenna, even if it's in the attic, then go that route.
Silver Sensor may be marginal at that distance, depending on your location and interior design.

which 4-bay bowtie do u recommend?

The Channel Master CM-4221 (aka CM-3021) is slightly higher performance due to the dense rear screen
and they're all about the same inexpensive cost.

However, if you want to hide it indoors behind a couch (like I used to do)
then the Winegard PR4400 or Antennas Direct DB-4 might be better looking.

Thanks for the recommendation. Quick Qs come to mind.
- Do they still catch good signal if I put it behind TV or even cabinet (on which tv is sitting)?
- I am currently using (temporarily) a Philips Silver indoor antenna (built-in amp). Does not catch more than 2 channels at a time for some strange reason. 'Highly' directional. How are the above antennas in that regard? Would I need an amp or would they pull in better signals? Also, are they also as directional?
- DB-4 seems quite big for the room. DB-2 seems more like a decent size?
- Is there any difference b/w Channel Master and Antenna Direct antennas? One better than the other?
- Ideally did not want to use an amp for the bedroom as well since I already have an amp in the basement that is connected to the attic antenna. Channel Master amp that I bought from Lowes connected to my RS 15-2160 antenna. If you still think I should get an amp, which one?

Indoor antenna placement is always problematic. Trial and error...
Higher is usually better (mine is at top of LR cathedral ceiling).
Away from walls and furniture is usually better.
Pointing out a window helps a lot.
Outdoors is always best.

DB-2 is probably better performance than Silver Sensor.
Preamps can be overloaded if you are close to ANY broadcast towers.
The additional loss of an indoor/attic location can extend the overload range.
Also being behind a hill.... Again: Trial and Error....

Your other questions were already discussed in this thread,
including Preamp Overload issues.

Any reason why you can't run the attic antenna signal (after C-M amp)
to both locations?

I would LOVE to get the attic antenna signal split working for the two TVs but for some reason it is not working. Posted the same issue in this thread: http://www.avsforum.com/avs-vb/showthread.php?t=584715.

For some reason the signal is not strong enough it seems...which surprises me since the cable run is smaller to the bedroom tv and even tried same amp from basement and also another amp from RS. Maybe you can suggest me something..that I might be missing. I would love to get that working.

Below is the text from that thread:

--------------------------------------------------------
Here is my situation:

Just bought a Sharp 37'' LCD TV for my bedroom with built-in HD tuner. My OTA feed from attic is currently going to basement.

- Tried sending the signal to bedroom by splitting at satellite hub in basement but signal does not seem to be strong enough.

- Tried splitting the OTA signal right from the antenna into the bedroom with shorter cable (since attic entrance is from bedroom closet) and still the signals seems to be weak.

- Even connected the same channel master amp from basement into bedroom and got only 1 or 2 channels while basement TV got 10 from same amp. Seems like my basement Sony XBR TV has better tuner and sharp does not.

- Connected an indoor antenna such as silver sensor RS bowtie, Radio Shack 15-1880 to Sharp TV and got some channels but again not stable.

Now assuming that Sharp TV's tuner is pretty crappy, is there a way to boost the signals A LOT so that it picks up the digital channels? Any recommendations? Love the Sharp TV otherwise but this OTA issue is making me have second thoughts about it.

You help shall be appreciated.

----------------

First, the 12.3 dB should have been 11.2 dB and was corrected above.

With a spectrum analyzer set to 300 KHz RBW. Measured the span for a DTV channel, them measured a NTSC channel (the aural FM carrier was NOT included). The DTV was about 3.7 times the width of the NTSC visual. 20 Log3.7 = 11.2 dB. Also created a 50% duty cycle pulse with a DC level of 1V (2V P-P), then set the duty cycle to 14% (50/3.7) which produced .28V DC level. 20 Log(1/.28) = 11.1 dB.


Further investigation revealed Peak-to-Average Power Ratios for ATSC and NTSC aren't all that much different:
8-VSB Peak-to-Average Power Ratio is 7 dB +/- 1 dB.
NTSC Peak-to-Average Power Ratio is 5.14 dB for Mid-Gray luminance level,
7.55 dB for Pure White and 2.23 dB for Pure Black. [That's 4.9 dB +/- 2.7 dB]

=====================================================
Fol. provides ATSC Grand Alliance Test Results (mid-90's) for percentage of time exceeded vs Peak-To-Average Power Ratio:
http://www.zenith.com/digitalbroadcast/downloads/ATSC%20Lab%20Test%20Results.pdf
This is in very close agreement with the numbers discussed above (from AUS report).

=====================================================
Fol. from Harris (transmitter manufacturer) provides Visual Carrier Peak-to-Average for analog NTSC-M, PAL, ATSC and DVB-T:
http://www.broadcastpapers.com/tvtran/HarrisAnalogDigitalTransmitters.pdf
These are as summarized above.
I would expect that under color bar test conditions, there would be more energy in the (negative) video signal,
since darker colors are at larger amplitude levels, and hence peak-to-average ratio might be in 3-4 dB region.
By the same argument, "typical" on-air signals would frequently have dark scenes that would approach
2.2 dB Peak-to-Average Ratio (i.e. more average energy for same peak power level).

The FM audio carrier can not be ignored in NTSC overload calculations.
Per Bob Chase's recent on-air tests, the average power appears to vary from 4 to 10 dB below the visual carrier.
The Chroma carrier is much lower and can be ignored.

I would LOVE to get the attic antenna signal split working for the two TVs but for some reason it is not working. Posted the same issue in this thread: http://www.avsforum.com/avs-vb/showthread.php?t=584715.

For some reason the signal is not strong enough it seems...which surprises me since the cable run is smaller to the bedroom tv and even tried same amp from basement and also another amp from RS. Maybe you can suggest me something..that I might be missing. I would love to get that working.

Below is the text from that thread:

--------------------------------------------------------
Here is my situation:

Just bought a Sharp 37'' LCD TV for my bedroom with built-in HD tuner. My OTA feed from attic is currently going to basement.

- Tried sending the signal to bedroom by splitting at satellite hub in basement but signal does not seem to be strong enough.

- Tried splitting the OTA signal right from the antenna into the bedroom with shorter cable (since attic entrance is from bedroom closet) and still the signals seems to be weak.

- Even connected the same channel master amp from basement into bedroom and got only 1 or 2 channels while basement TV got 10 from same amp. Seems like my basement Sony XBR TV has better tuner and sharp does not.

----------------

Can you describe in sequence, including model numbers, each component, including RF Splitters, etc the TV signal goes through?

Why is the Channel Master Amp in the basement? Because that's where twin-lead goes?
It should be as close to the antenna as possible in order to overcome the downlead cable loss.

When you added an RF Splitter, where in the chain did you insert it?
Of course, it will contribute 4 dB of loss.

If you are using a Satellite Multiswitch to merge the TV signal onto all of the outputs,
there could be another serious loss of signal, unless the C-M Amp preceeds it.

Ok.

RS Antenna (15-2160) in Attic (entry from my closet in bedroom). Connected to a Pre-amp CM 5041DBS (on lowes website). Using the internal cable running from inside home to back of house at the satellite hub. From the hub, I just used a connected to send a cable into my basement (drilled a hole right through) since TV is right behind hub. Cable goes into the power supply of the amp and then into the TV.

Now what I initially tried to do is put the Radio Shack splitter right near the hub so one cable goes into the basement and the other cable connected to the cable (via connected) that goes back into the bedroom. Seems that was too much distance for signal to come through and therefore did not even catch one channel in my bedroom Sharp TV. Even tried connecting various RS Antennas and also the CM antenna. Nothing.

Then, just for testing purposes I tried the dirty approach of running a cable right from attic through the room to the bedroom TV. Still nothing! I really thought that would work due to the shorter cable (50 feet). Even connected the same CM antenna from basement to Sharp TV but nothing...at that point determined that Sharp TVs tuner is surely weak since basement TV picked up 10-12 digital channels while Sharp TV picked about 2.

Right now I abondened the above approach have connected the Sharp TV to an indoor amp and am getting 2 channels (that too in the evening). And am waiting for input from you and others as to what I should be doing.

I am not using the satellite multiswitch for anything. I shall await your response. Thanks for the time taken to troubleshoot this for me.

See my post in your other thread. If you connected to the antenna with the pre-amp on it and didn't power the pre-amp then no signal would get through- a pre-amp blocks signals when not powered. A splitter would typically block the power to the pre-amp unless it had a DC pass through on the connection to the antenna.

replying to this post in the other thread as well.

See my post in your other thread. If you connected to the antenna with the pre-amp on it and didn't power the pre-amp then no signal would get through- a pre-amp blocks signals when not powered. A splitter would typically block the power to the pre-amp unless it had a DC pass through on the connection to the antenna.

Further investigation revealed Peak-to-Average Power Ratios for ATSC and NTSC aren't all that much different

For the purpose of pre-amp overload you are using 7 dB between DTV and NTSC stations is that correct? It works for me, but it will be interesting to see the final description of the 0 dBDTV from the IEEE. I could not find Bob Chase's on-air tests, do you have a link?

For station clock (sync) reference: PBS used to use three Cesium Beam clocks averaged together. We had two Grass Valley generators and I used to compare the phase angle (not frequency) between the two in degrees. On the HD production trailer we had a Leitch sync generator that could use the on board GPS receiver as a reference.

For fun: The peak-to-peak value 400 Hz and 1 KHz will remain the same regardless of the phase angle between them. The peak-to-peak value 400 Hz and 800 Hz (or any multiple 2nd, 3rd, etc. of 400) will change depending on their phase differences.

For the purpose of pre-amp overload you are using 7 dB between DTV and NTSC stations is that correct? It works for me, but it will be interesting to see the final description of the 0 dBDTV from the IEEE. I could not find Bob Chase's on-air tests, do you have a link?

For station clock (sync) reference: PBS used to use three Cesium Beam clocks averaged together. We had two Grass Valley generators and I used to compare the phase angle (not frequency) between the two in degrees. On the HD production trailer we had a Leitch sync generator that could use the on board GPS receiver as a reference.

For fun: The peak-to-peak value 400 Hz and 1 KHz will remain the same regardless of the phase angle between them. The peak-to-peak value 400 Hz and 800 Hz (or any multiple 2nd, 3rd, etc. of 400) will change depending on their phase differences.

I am trying to determine how to extrapolate the published NTSC Preamp specs for use with DTV signals.
NTSC signals are measured with a peak power meter (actually the average power within the blanking interval,
rather than instantaneous worst case peak voltage).
In order to treat DTV signals equally with NTSC, for a first order estimate, all we need to do is convert DTV's
average power into peak power by adding about 7 dB +/1 dB. [Give or take a few dB.]

If I were concerned about preventing clipping in the Preamp with a single DTV signal,
I might want to allow a little more "head room" to accomodate the infrequent instantaneous peaks.
I would rather not have any erasure errors in the Preamp, since they detract from on-air multipath error resistance.
NTSC would also have some instantaneous peaks, but not as much as DTV and clipping would have little effect

I am still working on how to handle the more complicated multiple signal derating.
The C-M and W-G spec points are for a 46 dB Cross Modulation level.
That means the NTSC (peak) intermod products on the output of the Preamp are 46 dB below the individual (peak) output signals.
The NTSC multiple signal (peak) power backoffs are probably in the same ballpark for DTV (peak) power, however,
the EFFECT of intermod products is quite different for DTV vs NTSC, NTSC vs DTV, DTV vs DTV and NTSC vs NTSC.

========================================================
See bobchase 9/24/05 post in Antenna Thread comparing on-air measurements for 8 antennas:
http://www.avsforum.com/avs-vb/showthread.php?t=381623&page=93&pp=30

FYI, also see bobchase 3/28/05 at 8:23pm post comparing outdoor vs attic on-air measurements:
http://www.avsforum.com/avs-vb/showthread.php?t=381623&page=58&pp=30
And bobchase 3/30/05 post at 8:31pm showing results for different attic locations:
http://www.avsforum.com/avs-vb/showthread.php?p=5410432#post5410432

2. Eons ago, NTSC signals were synchronized to the 60 Hz power grid.
Hence I would expect that all stations in a local area would have transmitted the first pulse in each frame
at almost the exact same time. At the Preamp, this would result in very large spikes.
I don't (yet) know whether there is synchronization of the 59.94 Hz frame rates from station to station.
This would be different than synchronizing to 5 MHz GPS/WWV and/or 60 kHz WWVB:
See "STANDARD" paragraph in fol: http://en.wikipedia.org/wiki/NTSC

Question for Bob Chase:
In your signal spectra charts, KUHT-TV (N08) had an unusual hump between 180 MHz and
the visual carrier at 181 MHz.

I see that this PBS station does datacasting, which presumably uses 8-VSB packets,
and hence would not cause this hump.

I wondered if you knew whether they might also be using something like the DotCast dNTSC datacasting system
(also used for MovieBeam) that adds a reduced level QAM carrier in quadrature onto the visual carrier?
Holl_ands,
KUHT does indeed DotCast but their chief & I have been playing phone tag. I'll let you know what I find out.

Bob Chase

I am trying to determine how to extrapolate the published NTSC Preamp specs for use with DTV signals.
Very good and thanks for the links.

I did a simulation in Workbench (using sine waves) of 5 UHF channels at various levels to see what the composite P-P value would be. You may find it interesting.

Channel dBmV In Volts
CH 20 -12.0 2.51E-04
CH 22 -17.0 1.41E-04
CH 35 -22.0 7.94E-05
CH 40 -8.00 3.98E-04
CH 52 -24.0 6.31E-05
The composite values: P-P = 2.56mV, RMS = .91mV or +0.87 dBmV

For equal levels
Channel dBmV In Volts
CH 20 0.00 1.00E-03
CH 22 0.00 1.00E-03
CH 35 0.00 1.00E-03
CH 40 0.00 1.00E-03
CH 52 0.00 1.00E-03
The composite values: P-P = 11.39mV, RMS = 4.0mV or +12.1 dBmV

Edited 09-30-2005 to correct RMS level
Edited 09-30-2005 to add equal channel levels

Further investigation revealed Peak-to-Average Power Ratios for ATSC and NTSC aren't all that much different:
8-VSB Peak-to-Average Power Ratio is 7 dB +/- 1 dB.
NTSC Peak-to-Average Power Ratio is 5.14 dB for Mid-Gray luminance level,
7.55 dB for Pure White and 2.23 dB for Pure Black. [That's 4.9 dB +/- 2.7 dB]

=====================================================
Fol. provides ATSC Grand Alliance Test Results (mid-90's) for percentage of time exceeded vs Peak-To-Average Power Ratio:
http://www.zenith.com/digitalbroadcast/downloads/ATSC%20Lab%20Test%20Results.pdf
This is in very close agreement with the numbers discussed above (from AUS report).

=====================================================
Fol. from Harris (transmitter manufacturer) provides Visual Carrier Peak-to-Average for analog NTSC-M, PAL, ATSC and DVB-T:
http://www.broadcastpapers.com/tvtran/HarrisAnalogDigitalTransmitters.pdf
These are as summarized above.
I would expect that under color bar test conditions, there would be more energy in the (negative) video signal,
since darker colors are at larger amplitude levels, and hence peak-to-average ratio might be in 3-4 dB region.
By the same argument, "typical" on-air signals would frequently have dark scenes that would approach
2.2 dB Peak-to-Average Ratio (i.e. more average energy for same peak power level).

The FM audio carrier can not be ignored in NTSC overload calculations.
Per Bob Chase's recent on-air tests, the average power appears to vary from 4 to 10 dB below the visual carrier.
The Chroma carrier is much lower and can be ignored.
Holl_ands,
What I haven't published is the CM7777 overload testing I was doing that morning. Although I have no problem sharing, I think I should redo it with two simutaneous sweeps. One in 'Max Hold' and the other in 'Average'. Then you can see the DTV average power vs DTV peak power. It will also capture the NTSC peaks. The off-air tests you reference above were done using a SA in 'View' mode and then averaging 100 samples. Which means that the NTSC power values shown are APL dependent and do not represent the peak power of the station. (APL = Average Picture Level)

NTSC transmitters are set up using average power. This is done by transmitting sync & blanking signals only. (No chroma, setup, or video information and the aural carrier disabled.) A demodulated wavform shows nothing above the 0 IRE scale and only the sync pulses below. The measured average power is multiplied by 1.68 to log the peak power. The aural carrier is then abled and set to where the station wants to run it (typically from 5% to 10% of peak power). The chroma sub-carrier plays a significant part in causing intermodulation products in a NTSC transmitter. However, I would agree that with the amount of carriers presented to a pre-amp in the Houston market, the chroma sub-carriers can be pretty much ignored for overload calculations.

When we setup or size DTV transmitters we use a 6.4 dB factor (that is often rounded down 4x) for peak to average power ratio. But that is based on 10E3 data samples. The tube manufacturer uses similar ratios when rating amplifier tubes. The newest E2V (aka EEV, aka Marconi) 3130 tube is rated at an output of 145 kW peak digital power and 35 kW average power. The same tube is rated at 88 kW NTSC visual only service or 77kW with 10% aural in a common mode amplification transmitter.

Bob Chase
KHWB-TV

Bob Chase

Downloaded your Antenna Test PDF file. Nice piece of work, the effort to test and document such a task is greatly appreciated. Anyone remotely interested in television antennas should download Bob’s Antenna Test (http://www.avsforum.com/avs-vb/showthread.php?t=381623&page=93&pp=30).

I really like the look of the spectrum data. Was the data imported into Excel and plotted or does the Agilent E4401B generate its own graphs?

Sorry to intrude on the subject but this looked like good spot to ask my question. I have just finished setting up a cm4228. I have a signal strengh of 74-89 atthe TV across the five channels that I receive. Can I get good results from a preamp with signal levels as high as these. I'm about 60 miles out from the towers.

Thanks

Bob Chase

Downloaded your Antenna Test PDF file. Nice piece of work, the effort to test and document such a task is greatly appreciated. Anyone remotely interested in television antennas should download Bob’s Antenna Test (http://www.avsforum.com/avs-vb/showthread.php?t=381623&page=93&pp=30).

I really like the look of the spectrum data. Was the data imported into Excel and plotted or does the Agilent E4401B generate its own graphs?
The 4401 will generate a low-res pcx file, if you ask it to. What you are seeing is an Excel chart with 4001 data points per band, per antenna. (One 4001 point sweep for the UHF band and another 4001 data point sweep for the VHF band.) Each sweep (U or V) for each antenna has it's own tab within the spreadsheet. That data is displayed in the charts. Each tab also has a look-up function to show the peak NTSC value and the mid-band DTV value of each Houston channel but that data does not show up on these charts.

Bob C

Eons ago, NTSC signals were synchronized to the 60 Hz power grid. Hence I would expect that all stations in a local area would have transmitted the first pulse in each frame at almost the exact same time. At the Preamp, this would result in very large spikes.
There is no station that has a station that is a frequency multiple (2nd, 3rd, etc.) of its self therefore there is little danger of individual cycles of RF adding together that would cause any problems. If they were then the chance of subtracting should be the same and that would probably cause problems. I can provide data if you like.

Sorry to intrude on the subject but this looked like good spot to ask my question. I have just finished setting up a cm4228. I have a signal strengh of 74-89 atthe TV across the five channels that I receive. Can I get good results from a preamp with signal levels as high as these. I'm about 60 miles out from the towers.

Thanks
The "signal strength" measurement of a DTV receiver is not really signal strength but some form of signal quality measurement so your signals are probably not too strong. If you really don't have any nearby TV towers than a Channelmaster 7777 amplifier will likely significantly improve the signal at the receiver input. This is because it has a lower noise level than your DTV receiver and being mounted near the antenna it will overcome the losses in the downlead. Of course as long as you get zero digital errors the DTV picture will be as good as it gets, the pre-amp will just give you more fade margin.

There is no station that has a station that is a frequency multiple (2nd, 3rd, etc.) of its self therefore there is little danger of individual cycles of RF adding together that would cause any problems. If they were then the chance of subtracting should be the same and that would probably cause problems. I can provide data if you like.

I wasn't concerned re RF adding, it's going to be different freqs that are randomized by multipath anyway.
I was more concerned about the Peak-Envelope-Power coinciding.

Very good and thanks for the links.

I did a simulation in Workbench (using sine waves) of 5 UHF channels at various levels to see what the composite P-P value would be. You may find it interesting.

Channel dBmV In Volts
CH 20 -12.0 2.51E-04
CH 22 -17.0 1.41E-04
CH 35 -22.0 7.94E-05
CH 40 -8.00 3.98E-04
CH 52 -24.0 6.31E-05
The composite values: P-P = 2.56mV, RMS = .91mV or +0.87 dBmV

For equal levels
Channel dBmV In Volts
CH 20 0.00 1.00E-03
CH 22 0.00 1.00E-03
CH 35 0.00 1.00E-03
CH 40 0.00 1.00E-03
CH 52 0.00 1.00E-03
The composite values: P-P = 11.39mV, RMS = 4.0mV or +12.1 dBmV

Edited 09-30-2005 to correct RMS level
Edited 09-30-2005 to add equal channel levels

If all of the sinusoid RF signals were initialized so that they start at 0 and then increase in voltage,
you will end up with a HUGE spike at the beginning....and maximum Pk/Avg.
Of course, real systems would have randomized starting phases.

Many data systems use a multi-tone FDM (Frequency Division Multiplex),
including COFDM, Wi-Fi, ADSL, SAT transponders and older HF modems.
The baseband peak-to-average ratio is very dependent on the relative starting phase for each tone at the beginning of each baud time.

Preamp overload performance is pretty much dependent on the active device used in the design. Some rough numbers:

lo-noise bipolar = -20 dBm
dual-gate MOSFET = 0 dBm
GaAsFET = +20 to +30 dBm
MMIC = 0 to +10dBm

I wonder what device is in the Channel Master and Winegard preamps? How long have these products been on the market? Are they some ancient dual-gate MOSFET design from the late 70's?

Ron

By overload, do you mean 1 dB compression point with one (or two) signals?
Or the Output 3rd Order Intermod Intercept Point (OIP3), which is typically 10-15 dB higher?

Preamp specs stipulate something that is much lower: the point at which the intermod products for multiple
UHF signals is suppressed by at least 46 dB for 2 channels (C-M) or 5 channels (W-G).

Maybe you can read the non-existent part numbers on the UHF section
of the fol. C-M Spartan Preamp....
[300-Ohm input on the left, 75-Ohm output on the right.]

If all of the sinusoid RF signals were initialized so that they start at 0 and then increase in voltage, you will end up with a HUGE spike at the beginning....and maximum Pk/Avg. Of course, real systems would have randomized starting phases.
At any given instance in time the total amplitude will be the algebraic sum of the RF signals. The same is true of acoustic pressure at any given point in space. See attached PDF file showing the RF signals.

Now try some randomized starting phases.
In practice a computerized search would find the optimum set that minimizes the Peak/Average Ratio.

Now try some randomized starting phases.
PDF file attached as requested.

I need some help, holl_ands is giving me a real workout ;) !!

Hey guys! I'm not sure if this a little OT, but I just reviewed a book @ Epinions called GEODESIC MATH AND HOW TO USE IT (http://www.epinions.com/content_197338435204).

I did refer to it a lot in antenna positioning & got most of my calcs from it as well. VERY useful reference on spherical trig & other stuff too. Well at least you know what I've been doing lately... ;)

I have constructed a lot of multiple channel, multiple antenna headends in which there is often a difference in signal level of as much as 30dBmV between the weakest and strongest DTV signals. I always can avoid developing a DTV load that even approaches any plausible maximum output rating of any preamplifier I use because I generally bandpass filter and pad down any inconveniently strong DTV signal and can drop a notch on any excessively strong analog signal if it concerns me. But then, I have to take that preamplified spectrum and power amplify it as much as possible, because the loop wiring systems used in high rise buildings does not facilitate the insertion of line extender amplifiers.

As I gradually increase the power output of my Blonder Tongue BIDAs to the range where I have speculated that the load might be exceeding safe operating parameters, I always lose the weakest channels first. In fact, since I never lose the strongest channels before I have so thoroughly degraded the quality of the weakest channels that there is no point in even further increasing the power level of the strongest to see at what output level some of my stronger signals might be clipped beyond the point at which they can be processed. And even if I amplified them to that level, I'd still be speculating that the cause of the signal processing failure was clipping, rather than other, excessive intermodulation products.

I don't profess to have any insight into what happens to a low voltage sine wave when it is present in the same circuit in which a strong signal is getting clipped, but I don't think it gets clipped. Or maybe it does when it coincides with the peak of some other sine wave.

I would expect that digital TV signals would be relatively immune to the effects of clipping, because the processing of those signals requires identifying "one" and "zeros", whereas analog audiophiles claim that they can tell the difference between audio created by signals that are carried to their speakers through oxygen-free copper conductors.

In a cable TV system, where all of the channels have been balanced to exactly the same level, there might be situations where the first unacceptable parameter reached and then exceeeded is the clipping level, but in an off-air system, I believe the first casualites of calculable overload will always be the weaker ones getting excessively corrupted by intermodulation products.

There is never going to be a "holy grail" signal level standard for off-air DTV signals comparable to what we have for analog because, among other things, the definition of acceptable performance is qualitatively different. We are presently satisfied that if we deliver, to the curb, an analog signal with an S/N ratio of 45dB and a peak carrier visual carrier level of 0dBmV, then we can rely on that signal to remain qualitatively sufficient to please discriminating viewers while incurring the normal range of signal quality deviations, but acceptable performance could include accepting the circumstance of one frame per second having an S/N of 40dB or 35dB , since it is humanly impossible for anyone to notice that. Yet if one DTV frame per five thousand has a glitch in it such that it impedes the processing of that frame, then once, over the course of a movie, the picture will jam or visibly block for one full second and the audio may get knocked out for even longer than that. I don't know how we're ever going to meaningfully mathematize the probability of some glitch disrupting our signal processing.

There is never going to be a "holy grail" signal level standard for off-air DTV signals comparable to what we have for analog because, among other things, the definition of acceptable performance is qualitatively different. We are presently satisfied that if we deliver, to the curb, an analog signal with an S/N ratio of 45dB and a peak carrier visual carrier level of 0dBmV, then we can rely on that signal to remain qualitatively sufficient to please discriminating viewers while incurring the normal range of signal quality deviations, but acceptable performance could include accepting the circumstance of one frame per second having an S/N of 40dB or 35dB , since it is humanly impossible for anyone to notice that. Yet if one DTV frame per five thousand has a glitch in it such that it impedes the processing of that frame, then once, over the course of a movie, the picture will jam or visibly block for one full second and the audio may get knocked out for even longer than that. I don't know how we're ever going to meaningfully mathematize the probability of some glitch disrupting our signal processing.
You could just as well argue that the digital signal is easier to quantify than an analog one since the transition from reception to no reception is more abrupt. Very brief signal glitches are corrected by the error correction coding of ATSC and most slightly longer glitches just result in such minor anomalies as a few macroblocks in the picture. Longer drop outs are caused by such things as strong multipath by an airplane flying directly in the wrong path but with analog the resulting flashing picture is also fairly obnoxious. I think the main problem with digital drop-outs may just be that the viewer doesn't know what caused them. All digital drop outs just cause a frozen or blank image where each analog problem causes a specific issue that the viewer can learn to accept because they expect such things as big noise flashes for lightning, slow-fast-slow flashing ghosts for airplanes, bands of sparkles when they run their vacuum cleaner etc.

AntAltMike,

I would expect that digital TV signals would be relatively immune to the effects of clipping, because the processing of those signals requires identifying "one" and "zeros",...

The digital signal is far from being immune to clipping or even moderate compression in an amplifier. Remember that the digital signal is an analog RF signal when it leaves the transmitter. The DTV receiver has to constantly decide at which one-of-eight levels the RF signal presented represents and, when the signal is compressed, will fail to do that.

And even if I amplified them to that level, I'd still be speculating that the cause of the signal processing failure was clipping, rather than other, excessive intermodulation products.

Compression and (eventually) clipping are the root causes of IMD. In truth, when someone argues that clipping is the problem and you say IMD is the problem, you are both rooting for the same team because your both saying the same thing, just in different ways. Compression causes IMD / IMD is caused by compression.

As to the strongest signal being just fine, yes, I would think that it would be. But that doesn't mean it isn't being clipped or compressed. Todays TV's can lock to a signal with almost no sync pulse. There are times while tuning the analog transmitter that I will see the consumer TV start to do flip-flops (one of the reasons it's there). I'll reset the waveform monitor to see the sync pulse and find only -10 IRE or so left. I'd had been concentrating on tuning the transmitters frequency response or the group delay so hard, I'd tuned my way into a corner and lost the sync pulse. A similar thing happens in your BT amps when you turn up the gain. As the gain is increased, the largest sync-tip compresses, perhaps even to the point of clipping, and all the while the IMD level climbs.

There is never going to be a "holy grail" signal level standard for off-air DTV signals comparable to what we have for analog because, among other things, the definition of acceptable performance is qualitatively different.

The 'holy grail' would be about 17 dB S/N or better. (Some STB's can't lock at 16 dB S/N, even if the signal it is perfect in every other way and at constant level). A reasonable question would be: "How often could the S/N drop below that level and the customer still find it acceptable?". I would think that if the TV locked up once an hour, then the viewer would eventually 'wear out' and stop watching OTA TV. A homeowner would opt for another delivery system. In the case of the loop-down systems you work on, call you to fix it.

2009 should be a good year for you. With all the OTA NTSC transmitters gone, your IMD levels will drop, increasing your systems effective S/N. Additionally, there may even be some gain available in your amps because you will not need as much headroom as you did before with NTSC gone. :cool:

Bob Chase

Non-linearity in the Preamp creates IMD, as can be seen in textbooks by doing a series approximation
to the non-linear Input/Output curve and inputting multiple signals.

When you drive the Preamp so that it is actually clipping more than a few peaks per second,
the resultant SFDR (Spurious Free Dynamic Range) will be severely limited.

Presuming an input thermal noise floor of -106 dBm, for a CM-7777 Preamp with N.F. = 2 dB and Gain of 26 dB,
the output thermal noise floor would be -78 dBm.

The C-M and W-G overload spec points are levels which will result in intermod products being at least 46 dB below the strong signals.
For the CM-7777 Preamp's 51 dBmV (2.3 dBm) output (peak power) overload spec point,
the intermod distortion products would be 5 dBmV (-43.7 dBm).

Hence sensitivity for weak signals is reduced by about 34 dB when operating at the overload spec point.

For every dB of back off from the overload spec point, there is a 3:1 reduction in the 3rd order intermod levels:
http://www.avsforum.com/avs-vb/showthread.php?p=6163454&highlight=spurious+dynamic#post6163454
Hence operating the CM-7777 roughly 8.5 dB below the overload spec point, reduces the intermod levels by 25.5 dB.
This means that the output intermod levels would be 46 + 25.5 = 71.5 dB below the strongest signals, or about 2.3 - 8.5 - 71.5 = -77.7 dBm.
This is the optimal operating point that maximizes the sensitivity for weak signals, i.e. the SFDR.

=======================================================
The fol. IEEE paper provides further discussion on this subject:
"Interference between Television Signals due to Intermodulation in Receiver Front-Ends", Charles Rhodes, IEEE Trans. Broadcasting, Mar 2005.

The fol. papers provide additional info re definition and measurement of Peak-to-Average Ratios:
"Measuring Peak and Average Power of Digitally Modulated Advanced Television Systems", Charles Rhodes, IEEE Trans Broadcasting, Dec 1992.
and
"Measuring Peak/Average Power Ratios of the Zenith/AT&T DSC-HDTV Signal with a Vector Signal Analyzer", Gary Sgrignoli, IEEE Trans Broadcasting, Jun 1993.
and http://www.boonton.com/2002/pdf/AN50.pdf

By overload, do you mean 1 dB compression point with one (or two) signals? Or the Output 3rd Order Intermod Intercept Point (OIP3), which is typically 10-15 dB higher?
1 dB compression point.


Maybe you can read the non-existent part numbers on the UHF section of the fol. C-M Spartan Preamp.... [300-Ohm input on the left, 75-Ohm output on the right.]
Many devices are available in surface mount, so the picture doesn't tell much. Due to the higher noise figure, I'll guess it's an MMIC design.

BTW, I wanted to thank you for turning us all on to Radio Mobile. Great program. I've been looking at the path from my location to the Sacramento DTV stations (for which I have a pretty good geometry) . Radio Mobile indicates that it's possible.

http://img87.imageshack.us/img87/4388/sac5oa.jpg (http://imageshack.us)

Ron

Must be Global Warming, looks like you're all under water.
Otherwise congradulations....as you can see, it really isn't all that difficult.

Under PICTURE PROPERTITIES, click on RAINBOW-COLORS to change elevation colors.
I usually use ABSOLUTE vs RELATIVE and chose elevation settings and colors to emphasize terrain of interest.
Dark Blue works good for ocean, but in order to minimize ocean "noise", I've found
I need to set the lowest scale in the 2-10 m region.

I still have some Yahoo User Group notes to go over to see if there is a "fix",
but I've found that the RAINBOW-COLOR selection under Polar Radio Coverage
apparently uses the same color definitions...so I keep resetting them back and forth.

Wideband GaAsFET preamplifier kit:

http://www.g0mrf.freeserve.co.uk/432LNA.htm

Ron

Wideband GaAsFET preamplifier kit
Ron, thanks for the info and link. Given the supply and bias voltages, what do you estimate the signal overload to be? Added: IM Test (http://www.qsl.net/yu1aw/ATF54143_70cm_IMD.gif). I think the pre-amp would need a suitable "Transient Suppressor" on the input.

BTW, You and I have conversed before about MPEG2 and Firewire. I did not realize you had an amateur radio affliction :) until I saw your beam antenna pictures in the antenna pictures thread.

1001001's
WA5RMP (not active)[Click below for my dish and TV antennas]

Wideband GaAsFET preamplifier kit:

http://www.g0mrf.freeserve.co.uk/432LNA.htm

Ron

Hey, that looks like fun. Good thing I've got a pick-and-place machine and an IR-reflow oven sitting in my basement. So I should have no problems assembling the kit. :)

Seriously, though, too bad they don't offer soldered boards. Doing SMT hand-soldering is not really my idea of fun.

On the plus side, it is simple enough to do by hand. Plus I *love* how the physical implementation matches the schematic. I work with standard cell ASICs in my day job. ASIC designers write RTL, which bears very little resemblance to the gates and wires in the final product.

I have had this preamp for a while: http://www.researchcomms.com/hdtv.html and finally installed it at the antenna replacing a Winegard AP-4700. It has a specified noise figure of 0.4dB. It made a noticeable improvement with signal qualities going up from 5 to 15 points on weak stations. As far as overload goes, in one direction I have one strong station at 13 miles running one megawatt WPXQ-DT. I see no sign of overload on a spectrum analyzer or on analog stations from it. In a different direction I have two strong stations at 11.5 miles WHPX analog and digital running 2.8 Meg and 90KW. I can see strong intermodulation products all over the UHF TV band on the spectrum analyzer and sync bars on analog station on the TV. John

I have had this preamp for a while: http://www.researchcomms.com/hdtv.html and finally installed it at the antenna replacing a Winegard AP-4700. It has a specified noise figure of 0.4dB. It made a noticeable improvement with signal qualities going up from 5 to 15 points on weak stations. As far as overload goes, in one direction I have one strong station at 13 miles running one megawatt WPXQ-DT. I see no sign of overload on a spectrum analyzer or on analog stations from it. In a different direction I have two strong stations at 11.5 miles WHPX analog and digital running 2.8 Meg and 90KW. I can see strong intermodulation products all over the UHF TV band on the spectrum analyzer and sync bars on analog station on the TV. John
Hi John. How does the overloading of the Research Communications pre-amp compare to what you had with the AP-4700?

John,
As near as I can tell it is about the same. John

Please tell me if I should post this in another thread.

I'm stuck using an indoor antenna for now). I'm in Los Angeles (about 20 miles from the broadcast tower according to antennaweb).

With my Sony's built in tuner, Iamb able to receive most (I think) of the available stations, but not all the time and not without much pain.
I'm continually having to adjust the antenna depending on the station, time of day, and more annoyingly, if I get up and move around.

I'm using a RS 1880, I think (I'm not home right now). I have a Zenith indoor antenna on order, I'd like to see if it can do a better job.

Is there any way to connect both antenna at the same time, hopefully so I don't have to adjust either one as much?

Can the simple Silver Sensor antenna that one uses to get hd channels OTA also be connected (e.g. by a jumper cable) to one's AV receiver and also use it to FM reception? Tx.

Can the simple Silver Sensor antenna that one uses to get hd channels OTA also be connected (e.g. by a jumper cable) to one's AV receiver and also use it to FM reception? Tx.
The silver sensor is designed for UHF TV only and would make a poor FM radio antenna. Just about any antenna designed just for FM would work better including a cheap twinlead T loop or rabbit ears.

FWIW I received my silver Sensor today, and after playing with it for about an hour I realized it's much worse than the RS 1880 I've been using, at least in my apartment in L.A.

Guess I'll have to suffer until I decide wether to go to cable or fight w/my apt. manager over upgrading my Dish Network antenna. I've read that HD from cable looks superior to satellite. Who knows?

FWIW I received my silver Sensor today, and after playing with it for about an hour I realized it's much worse than the RS 1880 I've been using, at least in my apartment in L.A.

Guess I'll have to suffer until I decide wether to go to cable or fight w/my apt. manager over upgrading my Dish Network antenna. I've read that HD from cable looks superior to satellite. Who knows?

Yes, I think it is true that HD via cable is better than from satellite. This is not inherent, but the statellite companies compress their signals a great deal, lowering quality.

New guy here so excuse if an answer is posted elswhere, I looked and couldn't find it.

DTV installed new dish and OTA 'wing' for local stations, I get some but not the weak ones. A friend gave me a CM-4228 and when I connect it to the OTA cable (diplexed with a satellite cable) it kills one of my satellite signals.

Anyone have thoughts? Balun bad? Antenna shorting out? ??

Thanks in advance.

Probably a bad diplexer. Not uncommon.

Greywolf,
I would agree with you that the diplexer is bad, except for the fact that it is working with the Wingard antenna now. I'm confused if it works with one but not another.

Thanks,
Mark

p.s. Go SOX!

Is the OTA "wing" amplified? If it is, then the diplexer that came with it passes power on both legs, and if it is used with a non-amplified antenna that uses a balun, then the balun will load down the LNB power source. This will almost surely knock out the satellite even transponders.

Thank you both for helping!
Yes the wing is amplified or at least a sticker says so. So do I need a different connector from the RG-6 cable to the two leads on the 4228?

You need this, a DC block between the diplexor and antenna:http://www.radioshack.com/product/index.jsp?productId=2062057&cp=&kw=dc+block&parentPage=search

Does anyone know of a source to purchase Funke antennas in the USA? I'm looking for a PSP.1925-5/12 VHF yagi. The only two places I could think of were CPC CO in the UK (but they don't apparently stock this model), and direct from Funke - but I can't find any contact info and not sure if they sell direct to end users. Just wondering if anyone out there has had luck buying Funke in the US. TIA.

Off the top of my head, MAX HD has some Funke antennas. I think he might have some PSP.1922s lying around, not sure about the 1925s, though.
The 1922s sure look nice paired up:
http://community-2.webtv.net/GregBarker/NewTowerAntennas/
He must have gotten the antennas to Indiana somehow. You should ask him. :)

He must have gotten the antennas to Indiana somehow:)

Yes,and it only took 3mo,persistence,and a bit of a hassle to get them.There's only two places in the world to get one of these individually,somewhere in Russia,and my garage :-) 89 dollars each incl frt UPS ground-48 states only.When they're gone,they're gone.E'mail or pm me.

Here's a link to a Russian site that has the only correct picture on the net.The pic on Funke's site is not accurate.

http://www.newkino.ru/shop.asp?sid=2&pid=13

I have a DB4 on order which should be here Monday. The best place to mount the antenna is on the SW side of our house:

a) the HDTV antennas are in that direction and no buildings would be in the way
b) close to the communications closet (<40')

However, the electrical grounding rod is on the NE side of the garage about 150' away.

So, would it be better to:

1) mount the DB4 on the SW side and run long (~150') grounding wires to the grounding rod.

2) mount the DB4 on the NE side of the house with short grounding wires but long COAX. I would probably have to mount the DB4 10' higher here.

3) mount the DB4 on the SW side and add another grounding rod running the risk of ground loop problems.

4) mount the DB4 on the SW side and run the grounding wires to the communication cabinets which are already grounded (ie splice the ground)

Any help would be appreciated.

Thanks,

Bryant

You probably won't notice any difference with any of the methods and all look okay except #3. It's possibly dangerous aside from the ground loop problem and a building code violation. Even that would work with modification. The equipment grounding rod and the building grounding rod would need to be bonded with a 6ga or better copper wire. See http://www.cinergy.com/surge/ttip08.htm for details. If I was in your shoes, I'd go for #4. Don't forget to ground any cable that enters the building near the point of entry.

Thanks Greywolf!

POSITIONING OF ANTENNA

I just bought the ChannelMaster 4221 to pick up HD channels and wondered which side should face the towers? The "screen" side or the side with the "x"s and other hardware? I'm not getting ANY channels with the screen side facing the towers so I'm assuming I'm 180 degrees off?

I also attached the antenna to a mount from a rafter so it's upside down. Is that ok?

Sorry for being dense. I've checked everywhere on the web for the correct installation setup and find nothing.

Thanks

Upsidedown is OK. The x's point to the station. John

Upsidedown is OK. The x's point to the station. John

Thank you, thank you.

Back to the attic!

I posted my DIY antenna thread over in the Tweak and DIY forum. I would love to get some feedback on ways to improve the performance.

Ericglo

Joining a VHF/UHF (DC HD and FM) and UHF (Balt HD) Antenna
I took the advice of a previous post a purchased a joiner to try and get both the DC and Balt channels. I have a VHF/UHF pointed at the DC towers for HD and FM and a UFH pointed at Balt for HD. I have also added an amplifier into the mix though it doesn't seem to affect either signal in any way.

The results were mixed in that only one of the connections (UHF) on the joiner showed any promise whatsoever. Didn't matter which antenna I connected, the UHF worked.

Any suggestions how I can get them both to work? If I had two RF connections on the TV, I would buy the Silver Sensor to take the place of the DC antenna but that's not an option.

Thanks

I just bought a splitter/joiner from the shack at lunchtime and I'll try this tonight to see if I can get two antennas to work. Heck, it's a $5 try. It would probably be better spent at the local SB coffee shop.

We'll see. :cool:

As an update, the $5 splitter/joiner from the Shack worked better than my original joiner and now I get almost all of the Balt and DC HD channels except for one, WUSA 9.1 CBS. I receive ch 9 (WUSA analog) but no 9.1? I get 7.1 and 11.1. Any ideas?

Thanks

I have had this preamp for a while: http://www.researchcomms.com/hdtv.html and finally installed it at the antenna replacing a Winegard AP-4700. It has a specified noise figure of 0.4dB. It made a noticeable improvement with signal qualities going up from 5 to 15 points on weak stations. As far as overload goes, in one direction I have one strong station at 13 miles running one megawatt WPXQ-DT. I see no sign of overload on a spectrum analyzer or on analog stations from it. In a different direction I have two strong stations at 11.5 miles WHPX analog and digital running 2.8 Meg and 90KW. I can see strong intermodulation products all over the UHF TV band on the spectrum analyzer and sync bars on analog station on the TV. John

Are you saying this is better than the AP4700? How can I order one of these? Do I have to order directly from the UK? What kind of price are we looking at?

I have a DAT-75 roof mounted on a CM rotator. No pre-amp or distribution amp. Local and distant (11 mi to 60 mi) OTA HD channels are pretty good if I don't split the signal. Splitter leads to blocking and fluctuating signal strength. I use QS RG-6, and place the splitter at the distribution point in the basement (about 40' between antenna and splitter, then 30' to each receiver). Since I have two RG-6 leads from the attic, am I better off splitting the signal there, and running 70' to receiver, or leave as is?

Thanks,

Geordon

The Research Comm. preamp is the best one out there for receiving weak signals. I paid $150 US including shipping for it. I contacted them via E-mail and used a credit card.
If your receiption is OK without splitter or preamp, any preamp will probably improve the signal, if you do not get overload. With one station close you should try to get a preamp with as low gain as possible. The preamp should be located at the antenna. The splitter can be put anywhere between the receivers and the power inserter. John

The Research Comm. preamp is the best one out there for receiving weak signals. I paid $150 US including shipping for it. I contacted them via E-mail and used a credit card.
If your receiption is OK without splitter or preamp, any preamp will probably improve the signal, if you do not get overload. With one station close you should try to get a preamp with as low gain as possible. The preamp should be located at the antenna. The splitter can be put anywhere between the receivers and the power inserter. John

You got a real good deal. I was just quoted 143 GBP for the 9250 preamp + 9251 power supply + S&H, which converts to $250 US!

Guess I will have to go for the $50 AP-4700. Oh, well...

Geordon

I did not get the power supply. John

I did not get the power supply. John

That would save me $75 plus some shipping, hopefully. Much closer to your number. What would I use, instead? Do you have a Radio Shack PSU?

The AP-4700 might be too much amp, right? If I don't get the 9250, would the DHP-296 be a good choice?

Geordon

I have a grounding question.
Sorry if this is the wrong thread, but as I read along it became apparent some knowledgable people are reading this.
Anyway, I just installed an antenna-pre amp & rotor to my chimney and need to ground the whole set up. I understand I need to use a grounding block at the nearest point of entry.
Here is my problem, there is no direct route to the ground from my chimney. The grounding wire would have to lay on my roof. Actually my chimney lies in two valleys so the ground wire would have to go up before it could go down to the ground.I know this would be look bad but would it be safe?
The second option would be to run the ground wire into the attic then ground to a pipe or possibly back outside at a less conspicuous place. Is this second option safe? If so do I then need to use a covered wire?
Thanks in advance!

That would save me $75 plus some shipping, hopefully. Much closer to your number. What would I use, instead? Do you have a Radio Shack PSU?

The AP-4700 might be too much amp, right? If I don't get the 9250, would the DHP-296 be a good choice?

Geordon
I think you mean the Winedgard HDP-269 right? That is a good choice for an amp that does not overload easily.

I think you mean the Winedgard HDP-269 right? That is a good choice for an amp that does not overload easily.

I meant Winegard HDP-296. I see we both have butter fingers. Thanks.

The second option would be to run the ground wire into the attic then ground to a pipe or possibly back outside at a less conspicuous place. Is this second option safe? If so do I then need to use a covered wire?
Thanks in advance!

The whole point of the entry ground is to try and keep lightning out of the house. Wouldn't do much good to run it back into the attic. Your first option sounds better.

The NEC allows a ground wire to run inside the house. As of the 2002 code revision though, it does not allow grounding to a cold water pipe unless the connection to the pipe is within five feet of the pipe's entry to the building and the electrical panel is also grounded to the pipe within that same five foot length. The purpose of an antenna/dish grounding wire is not to conduct lightning to ground but to conduct any wind induced static buildup to ground and lower the chance of a lightning strike.

I live 31 miles away from Chicago and need to get a antenna that can be mounted in my attic(wife refuses to let me do this on the roof). All the antenna that I have found that could be installed in the attic are either uhf or vhf but not both for that distance. If anybody knows of an antenna that would work for me I would greatly appreciate your help. :D

You can place a roof-mount antenna in your attic. The question is, do you have the space for it, especially if you need to put it on a rotor. Note that your roof will significantly reduce your signal strength of any antenna in the attic, as compared to mounting outside on the roof.

..................................(wife refuses to let me do this on the roof). :D :D

I have a grounding question.
Sorry if this is the wrong thread, but as I read along it became apparent some knowledgable people are reading this.
Anyway, I just installed an antenna-pre amp & rotor to my chimney and need to ground the whole set up. I understand I need to use a grounding block at the nearest point of entry.
Here is my problem, there is no direct route to the ground from my chimney. The grounding wire would have to lay on my roof. Actually my chimney lies in two valleys so the ground wire would have to go up before it could go down to the ground.I know this would be look bad but would it be safe?
The second option would be to run the ground wire into the attic then ground to a pipe or possibly back outside at a less conspicuous place. Is this second option safe? If so do I then need to use a covered wire?
Thanks in advance!
The wire can lay on the roof and it can be bare copper wire. Ground the mast and the coax entry point at the closest place possible. If the power company ground is not the closest, drive a ground rod in the ground and connect the mast & entry point grounds to the rod. Then run a ground wire from the ground rod to the house's main power company electrical ground. The two ground sources must be bonded together electrically to meet code. Bonding prevents ground loops from forming betweent the difference of potential of the 2 ground sources. A ground loop can eventually kill electronic equipment.

......traderdan: At 31 miles, an attic mount is trial and error, nothing definite. You will need a large antenna, at least.

..traderdan: Check out Winegard and Channel Master for a wide range of antennas. 'stark electronics' is a good retailer.

... All the antenna that I have found that could be installed in the attic are either uhf or vhf but not both for that distance...

Install separate UHF & lowband VHF antennas, like the Channel Master CM 3021 UHF antenna (http://www.starkelectronic.com/allant.htm) and the AntennaCraft Y5-2-6 lowband VHF (chs 2-6) antenna (http://www.starkelectronic.com/acantena.htm#Y5).

Combine them onto one downlead coax with a Channel Master CM 7777 VHF/UHF preamp (http://www.starkelectronic.com/allamps.htm), which has separate coax inputs for VHF & UHF antennas.

Search each of the page links above for the specific equipment.

I just installed a DB8 in the attic above my garage and am attempting to receive the Kansas City digital stations, in particular the Fox affiliate which just went to full power. I am 50-60 miles west in Topeka with no major hills between myself and the transmitters, (hey, it's Kansas! LOL).
I'd like to know what might be the best pre-amp to use with the DB8 to enhance my chances of receiving any signals from K. City; (so far, nothing).
The power supply will be inside with about a 50 feet run of RG6 to the antenna. Lastly, I don't want to over-power the local Topeka digital broadcasts if possible.
Any help appreciated.
Bish

Many people on this forum (myself included) have had excellent results with the CM 7777 VHF/UHF preamp (http://www.warrenelectronics.com/antennas/7777.htm). It is very low noise, which is important for good digital reception. I currently use one connected to a Silver Sensor antenna in the attic to receive stations ~60 miles away.

Where I lived closer to town, I used a CM 7777 because a couple of stations then were very low power. The preamp never overloaded the full power stations. YMMV, of course, depending on the tuner and antenna you are using.

when did the fox affiliate go to full power? I have gotten it twice with a antennae with pre-amp someone gave me. It's really nothing more then rabbit ears--I have thought about an outdoor antennae but at this point it would only be for that fox station unless I could get an ABC station..

I get nbc locally hi def with analog which is the only reason I uses the indoor antennae. Is anyone in topeka getting anything from ABC hi def?

when did the fox affiliate go to full power? I have gotten it twice with a antennae with pre-amp someone gave me. It's really nothing more then rabbit ears--I have thought about an outdoor antennae but at this point it would only be for that fox station unless I could get an ABC station..

I get nbc locally hi def with analog which is the only reason I uses the indoor antennae. Is anyone in topeka getting anything from ABC hi def?

I live in Meriden, 15 mi NE of Topeka, and I can get KMBC 9.1 out of KC with rabbit ears. Others in Topeka have reported getting 9.1 with Channel Master 4228. The local ABC affiliate does have a digital signal but does not broadcast Hi Def.

Curious: how do you get hi def with analog?

analog is antenna right?

I switch back and forth between cox and what I call analog.

I got the new sony which gives me 4.1 infrequenty, 11.1,11.2,11.3, 13.1, 27.1, 44.3, and 49.1. 4.1, the 11's, 13.1, 44.3, and 27.1 are hid def. When I switch to cox obviously I can only get wibw hi def so in reality the only good my antennae does is give me nbc hi def and the occasional 4.1 fox hi def. abc looks better 49.1 then cox but at 480 pi is not going to be hi def. all digital channels on cox look good but my channes 2-73 have a little to be desired on a 60" screen

if you get a chance go check out the new sony sxrd--I got it from nebraska furniture mart initially but best buy matched the price here in topeka

An antenna can be used for analog and/or digital OverTheAir channels.

What an absolutely great thread! The first post with all its' links is pure gravy.
Looks like I have a lot of reading material to dive into.
....and to think, all I started out to do was buy an antenna..... :)

Does any one know what the warranty length is for a Channel Master 7777 ?

Check with AVSForum site sponsors or Warren Electronics (http://www.warrenelectronics.com/antennas/7777.htm) at their home page.

Need some suggestions on weak signal on only one station. I have a outdoor large uhf/vhf antenna. my locals are coming in from 2 differant directions approx. 195degs and 281degs. the channels 4,5,9,12 all feed into my sat receiver and register about 88-92 signal strength while ch 35(281deg) comes in at 60 signal strength. Towers for 4,5,9,12 are only 11mi while 35 is 43mi away. I have found that these signal strengths are coming in with attenna pointed at ch 35.

My question is could i add a preamp to help ch35 signal(boost) without messing up the other stronger signals and what if any preamp would work best??

If you have VHF & UHF digital channels (check your address at antennaweb.org), use the CM 7777 preamp in the link above your post. If UHF only, get the CM 7775.

Another question please. How much attenuation would large trees directly in the path of attenna to towers effect the loss of signal.

It depends on the type of trees, thickness of trees, and even the frequencies the stations are broadcasting on. Can't tell from here.

I think the worst problem with trees is signal strength fluctuation in the wind, which can play hell with some digital TV tuners. Newer ones are more immune to the problem though.

I bought one of those RS tuners because the clearence price of $90 was too low to resist. I am not sure what the SNR number represents but it is not based on the AGC value or channel power for an analog station. The channel power does seem to affect the signal strength level. When I tune to an analog station number (after clearing all channels by doing an auto re-scan with the antenna unconnected) The SNR number is usually an erratic 17 dB regardless of how strong the station is but the bar graph and signal strength readout is a consistant 49% for strong stations. Both those values seem to have more meaning when tuned to a digital station but I don't think you can read RF signal strength using them..

Most of thread is lost on me, but this response sounds like it may relate to a problem I am having. I'm experimenting with a RS Accurian tuner, and cannot get it to give me a picture on any station. For any reasonably strong station, the tuner seems to "peg" at a signal strength of 49%, and I get no picture. I use a long distance roof antenna, with a CM0064 amplifier. Only one station in my area is HD, but it is a strong station. According to the Accurian, though, even that one is still a "49".

I was assuming my RS tuner had some sort of defect until I saw your post. Any explanation you can offer for this 49% symptom, and how I might overcome it, would be greatly appreciated.

The R-S HTS-6000 Accurian Tuner only receives ATSC digital stations, not analog:
http://www.avsforum.com/avs-vb/showthread.php?p=6335957&highlight=analog#post6335957

Most of thread is lost on me, but this response sounds like it may relate to a problem I am having. I'm experimenting with a RS Accurian tuner, and cannot get it to give me a picture on any station. For any reasonably strong station, the tuner seems to "peg" at a signal strength of 49%, and I get no picture. I use a long distance roof antenna, with a CM0064 amplifier. Only one station in my area is HD, but it is a strong station. According to the Accurian, though, even that one is still a "49".

I was assuming my RS tuner had some sort of defect until I saw your post. Any explanation you can offer for this 49% symptom, and how I might overcome it, would be greatly appreciated.
What I was referring to was how the Accurian reacts when you tune to an analog NTSC station. Since it only receives digital stations you get no picture and if the station is strong the meter reads a consistant 49. What you need to do is tune the digital station. One way to do that is to do an autoscan, the tuner will report the number of channels + subchannels that it finds. Another way is to key in the actual digital number the station broadcasts on. You can find that out by going to www.antennaweb.org and following the choose an antenna link. In the final output page where it lists all the stations the last column labelled frequency assignment will show the channel number the digital station is on. After the box tunes a station one of these two ways you should be able to select it using the old analog channel number which it will re-map internally to the digital number.

I currently use a Channel Master 4228 antenna hooked up to a Channel Master 7777 Pre-Amp. The inside power source for the CM7777 Pre-Amp only has one out, and I'd like to get something that outputs at least four cables.

Can I just pick up a Channel Master Amplifier with four outputs at Lowes, or do I need to pick up a special hook-up to go with the CM7777, or do I just need to make sure that the amps have the same power specifications so I don't fry my CM7777?!

Thanks!
~Alan

I currently use a Channel Master 4228 antenna hooked up to a Channel Master 7777 Pre-Amp. The inside power source for the CM7777 Pre-Amp only has one out, and I'd like to get something that outputs at least four cables.

Can I just pick up a Channel Master Amplifier with four outputs at Lowes, or do I need to pick up a special hook-up to go with the CM7777, or do I just need to make sure that the amps have the same power specifications so I don't fry my CM7777?!

Thanks!
~Alan

What you need is a 4-Way Power Splitter:
http://www.radioshack.com/product/index.jsp?productId=2062051&cp=&kw=4-way+splitter&parentPage=search
http://www.radioshack.com/product/index.jsp?productId=2103099&cp=&kw=tv+splitter&parentPage=search
http://www.radioshack.com/product/index.jsp?productId=2103925&cp=&kw=4-way+splitter&parentPage=search

You should also be able to find them at Lowes, Circuit City, Best Buy, et. al.

The output of the C-M Power Insertion Module feeds the input of the Splitter and then you have four outputs to distribute...

What you need is a 4-Way Power Splitter:
http://www.radioshack.com/product/index.jsp?productId=2062051&cp=&kw=4-way+splitter&parentPage=search
http://www.radioshack.com/product/index.jsp?productId=2103099&cp=&kw=tv+splitter&parentPage=search
http://www.radioshack.com/product/index.jsp?productId=2103925&cp=&kw=4-way+splitter&parentPage=search

You should also be able to find them at Lowes, Circuit City, Best Buy, et. al.

The output of the C-M Power Insertion Module feeds the input of the Splitter and then you have four outputs to distribute...

I purchased the one from the top link. However, when I hook it up, my signal on my local FOX affiliate's digital signal drops down from upper 80s to 50-70 range (depending on when you look at it), and my NBC affiliate's signal goes from 70 to 40. Also, one of the other feeds an analog tuner, and I can't pick up several channels that I can get just great if I hook it up direct.

Please advise... thanks!

~Alan

Re: Coax ground

I am going to mount my new antenna on a telesocpic mast. This mast will be mounted to the side of my house and actually standing on my concrete patio. The point of entry of the coax will be into the attic. I will be grounding the mast properly. My question is whether it would be best to mount the coax grounding block to the mast (12 in. from attic entry) which would self ground due to attachment or mount it on the side of the house and run a ground wire. If I can't put it on the mast, can I mount it on the house and run a ground wire to the mast? I just don't really see the point of running 2 separate wires to the grounding rod.

I would mount it on the mast. It's a nice, neat installation. What you are missing though is the mast must be connected to the main building ground with a 6ga copper bonding wire. Any grounding point, secondary rod, mast in concrete, etc., must be bonded to the main building ground by code. An effectively single point grounding system must be maintained.

greywolf,

I will ground the mast to a grounding rod about 15 ft. away from the mast and also connect this rod to the house main ground about an additional 40 ft. away.

Thanks!

From TV Technology,

http://www.tvtechnology.com/features/On-RF/2006.01.25-f_doug.shtml
TVTechnology - RF Technology

Crazy Enough to Build Your Own TV Antenna?

This month, I'll take another look at receive antennas for DTV. My article "Antennas for DTV Reception" in the March 6, 2002 column on antennas for DTV reception was published almost four years ago, yet hardly a week goes by that I don't get a request for Fig. 1, which shows the dimensions for a do-it-yourself UHF TV rhombic antenna. The article is available at www.tvtechnology.com in the Doug Lung on RF section. I've reprinted Fig. 1 here. Refer to the original article for information on how TV antennas work and suggestions for building your own.
http://img.photobucket.com/albums/v637/keenanj/2006.jpg

Although I've received many requests for Fig. 1, I haven't received as many reports on how the antenna worked. I guess some readers found the size of the elements made construction more difficult than they thought or they built the antenna and weren't happy with the performance. As noted in the article, a rhombic that's five wavelengths on a side (about 100 inches at 600 MHz) will provide a predicted gain of approximately 12 dB. You will see later that smaller commercial TV antennas provide gains close to or greater than this.

RHOMBIC ANTENNAS

If you want to build a huge VHF TV antenna, an article from 1951 by Richard J. Buchan may be helpful, (See http://members.fortunecity.com/wtfdamem/Rhombic1.html). The antennas described are much bigger than the one I referred to. Buchan describes how a three-bay rhombic can be constructed with gain of more than 100 (20 dB). He notes that even though rhombic antennas are broadband, separate antennas will be needed for low VHF and high VHF, although the high-VHF rhombic can be strung inside the low-VHF rhombic using the same supports.

The article gives construction details, including a parts list, mast construction hints, dimensions and drawings for single bay and two bay antennas. If you want distant VHF-TV reception in a single direction and have the real estate, check it out!

A "Dual Rhomboid" antenna developed by Edmund Laport of RCA was modeled by L.B. Cebik and determined to have gains between 15 and 16 dB at 1296 MHz. This design should be able to be scaled for use at TV frequencies, (See http://www.cebik.com/vhf/rh.html l). In researching this article, I found what must be the ultimate UHF rhombic antenna, if it works as claimed. The Sveriges DX-FŸrbund Web site ( http://www.sdxf.org/alfa/dxinfo/Antenna%20Articles.pdf ), has a 60-page article on antennas. On p. 35, there is a description of DHR (dual hexamerous rhombic) antenna designed for the 430 MHz band. It should work well at UHF frequencies. The calculated gain of the 2x6 rhomboid antenna is 33 dB! Unfortunately, author Wayne Sarosi said details would be provided in a future posting, but I haven't been able to find it. If anyone can provide details on the DHR antenna, please e-mail me and I'll share the information.

Broadcast engineer Jeremy Lansman at KYES in Alaska has put together an excellent Web page titled "About TV and FM Antennas" at http://kyes.info/antenna/antennadex.html. The page contains links to articles on how TV antennas work, common TV and FM antenna types, and, of relevance to this article, a section devoted to building your own TV or FM antenna.

PRO PERFORMANCE

In my Dec. 14 RF Report (available at http://www.tvtechnology.com/dlrf/issue.php?w=2005-12-14), I reported that in the FCC's report to congress on the DTV field strength standards and test procedures for the Satellite Home Viewer Extension and Reauthorization Act of 2005, the commission found no specific changes are needed to the DTV field strength standards and/or planning factors.

The comments filed by the ABC, CBS and NBC affiliate associations in the proceeding included an exhibit by consulting engineer Jules Cohen with a survey of available TV receive antennas and amplifiers. In the report, the FCC cited this survey to show there are antennas currently available that meet or exceed the planning factor criteria. It should be useful if you decide to buy rather than build your own antenna. The affiliate associations' filing can be downloaded using the at http://gullfoss2.fcc.gov/prod/ecfs/

comsrch_v2.cgi. Enter 05-182 in the "Proceeding" box and scroll through the listings.

FCC DTV planning factors are based on antenna gains of 4 dB, 6 dB and 10 dB for low-VHF (Channels 2-6), high-VHF (7-13) and UHF (14-69) respectively. Kerry Cozad of Dielectric measured the Channel Master Model 4228 eight-bay bowtie-with-screen UHF antenna and measured gains of approximately 3 dB, 9 dB and 15 dB for low-VHF, high-VHF and UHF. This UHF-only antenna exceeds the planning factor gain at both high-VHF and UHF!

For VHF-only reception, the Antennacraft Model CS1100 claims an average low-VHF gain of 6.9 dB and an average high-VHF gain of 9.6 dB. The Channel Master Model 3610 doesn't do as well at low-VHF, with an average gain of 5.8, but provides a claimed average gain of 11.4 dB at high-VHF channels. While combined UHF and VHF antennas usually do not work as well as separate antennas, the Winegard Model HD7084P specifications show gains from 6.2 to 7.6 dB at low VHF, 10.8 to 12.0 at high VHF and 14.6 dB in the UHF band.

In a table in his exhibit, Jules Cohen shows that if a low-noise amplifier is used at the antenna, reducing the system noise figure to 4 dB, the media noise limited field intensity for DTV reception drops to 19.8 dBµ at low-VHF, 25.8 dBµ at high-VHF and 34.2 dBµ at UHF, based on receiving antenna gains of 6 dB at low-VHF, 10 dB at high-VHF and 12 dB at UHF.

In addition, CEA has an excellent Web site, AntennaWeb.org that allows you to see what TV stations are available at a specific address and what size antenna is required to receive them.

I purchased the one from the top link. However, when I hook it up, my signal on my local FOX affiliate's digital signal drops down from upper 80s to 50-70 range (depending on when you look at it), and my NBC affiliate's signal goes from 70 to 40. Also, one of the other feeds an analog tuner, and I can't pick up several channels that I can get just great if I hook it up direct.

Please advise... thanks!

~Alan
In your earlier posts, I see that you also have a Dish system.

First of all, are you using a simple connection on its own downlead (e.g. antenna-balun-preamp-downlead-powermodule-RFSplitter-HDTV etal)?
The power insertion module must be able to supply D.C. power to the Preamp, without any D.C. blocking RF Splitters or Diplexers in the way.

If it is a shared SAT/TV downlead, can you descibe all of the components?
Pay close attention to which port(s) on the SAT/TV Diplexers are marked as being "DC PASS".
The SAT Receiver provides DC power to the Dish via the "DC PASS" ports.

Great care must be taken if you are using both a SAT Receiver and a Preamp, to make sure that they are not shorting each other out.

===============================================
If you are using SAT/TV Diplexers at each end, temporarily try it with the SAT system removed from the downlead.
You can use some in-line coax connectors to bypass both Diplexers.

This will tell you if the SAT system is adversely affecting your TV system.

====================================================
A CM-7777 should have more than enough gain to drive a downlead (maybe 4-6 dB loss) and 4-way splitter (8 dB loss on each leg).
The overall loss of sensitivity due to downlead/Splitter loss is reduced by the amount of gain in the Preamp and hence should only be on the order of a dB or so.

However, you could use a 2-way splitter with one output feeding your HDTV and the other output feeding the 4-way splitter.
This would result in only 4 dB loss for the HDTV at the expense of 12 dB loss for the other components.

You may not like the results for the other TV's, but it does provide one more data point re how critical the splitter loss may be.

====================================================
You may be thinking of adding a Distribution Amplifier to boost the gain on top of the CM7777's already ample gain.
However, this could easily result in overloading the input of the HDTV's and TV's,
unless you are quite a ways from all transmitters.

It would help if you could provide your location to whatever accuracy you feel comfortable with:
zipcode and/or nearby cross streets (+/- a few miles is fine).

First of all, are you using a simple connection on its own downlead (e.g. antenna-balun-preamp-downlead-powermodule-RFSplitter-HDTV etal)?
The power insertion module must be able to supply D.C. power to the Preamp, without any D.C. blocking RF Splitters or Diplexers in the way.

Last night, I played with it again and found out that it was the coax cable going from the output on the splitter into the input of the HD-TiVo. It worked fine going straight from the output of the power insertion module into the HD-TiVo, but did NOT like it when the splitter was added to the mix. I now have a steady reliable signal (or at least as steady as it was before!)

Also, my current connection is antenna/balun/preamp/downlead/grounding block/downlead/powermodule/RF Splitter/assorted electronics... however, that is about to change. I'd like to take my antenna feed, and diplex the antenna feed into two rooms. What would be the best way for me to do this?!

~Alan

What do you mean by "Diplex"???
Do you mean taking one of the 4-way splitter outputs, running in through a 2-way splitter and thence to the other rooms, where it then gets split some more???
If this is the case, you probably need a multiple output Distribution Amplifier, instead of the 2-way splitter.


Or do you mean sharing the same downlead for TV and SAT??? Which could get rather complex....
I know you said you have Dish, so we don't yet know if the fol. will be issue when Dish upgrades for MPEG4.
I've read that the new MPEG4 DirecTV 5xLNB Dish is apparently incompatible with sharing the downlead.
So sharing the downlead may only be a temporary arrangement.....maybe you are better off with separate runs.....

Also, my current connection is antenna/balun/preamp/downlead/grounding block/downlead/powermodule/RF Splitter/assorted electronics... however, that is about to change. I'd like to take my antenna feed, and diplex the antenna feed into two rooms. What would be the best way for me to do this?!

~Alan

Alan,
I've got the following setup in my attic, and it's working well for me:

CM 4228 UHF antenna and a UHF dipole connected to a splitter (used in reverse as a combiner) with the output going into the UHF input of a Channel Master 7777 preamp. (The 4228 is aimed south for WCTV-DT and the dipole is cut for channel 17 - WALB-DT and oriented NE/SW to receive that signal) There is only about a foot of RG-6 between the balun of the 4228 and the combiner and between the dipole and the combiner.

I have a VHF dipole feeding the VHF input of the 7777 preamp. This is oriented to receive WFXL-DT.

The preamp is connected via RG-6 to the preamp power supply. The power supply output feeds the antenna input of a 5x8 multiswitch with the 4 RG-6 cables from the DirecTV 3 LNB dish feeding the four satellite inputs.

Two of the multiswitch outputs go to the HD Tivo. One of the lines feeds a diplexer which in turn feeds one of the satellite inputs and the antenna input.

Two more of the multiswitch outputs similarly feed a SD Tivo in the living room.

One of the multiswitch outputs feeds a SD receiver in the bedroom with a similar diplexer setup.

The remaining 3 multiswitch outputs are unused.

Since all this is in the attic, weatherproofing wasn't an issue, nor is windloading. As a result, it is all a bit "flimsy", but works fine.
Don

Or do you mean sharing the same downlead for TV and SAT??? Which could get rather complex....
I know you said you have Dish, so we don't yet know if the fol. will be issue when Dish upgrades for MPEG4.
I've read that the new MPEG4 DirecTV 5xLNB Dish is apparently incompatible with sharing the downlead.
So sharing the downlead may only be a temporary arrangement.....maybe you are better off with separate runs.....

Currently, I have the 4228 (http://members.aol.com/dreamworker23/100_0140.jpg) running directly from the Pre-Amp down to the grounding block, and then straight into the Den and then hooked up to the power insertion module, and then to the four way splitter that you recommended. This feeds my HD-TiVo, TV, a modulator (that I use to allow me to watch SD recorded material on my bedroom TV), and one for future use.

My antenna is ONLY used in the Den. However, after getting tired waiting on DirecTV to add SD-LIL for my DMA, and hearing of the WB-UPN merger which will allow me to receive CW programming from a neighboring market's UPN station, I decided that I would like to purchase a Stand-Alone TiVo for the Living Room.

I would like to take a splitter and then bring a line from it to near my Multi-Switch, and then diplex the antenna into two feeds (one of the lines going to a SD DirecTiVo in the Living Room, where the Stand-Alone TiVo will go, and then into another bedroom with another line coming from the multi-switch to a SD DirecTiVo).

So, what do I need? A splitter to split the line going from the antenna to the Den, and then two Diplexor sets to diplex the lines. However, do I need to get another amplifier to the other two rooms, or will the current power module still provide power to these other two runs?!

As far as DirecTV goes, I assume that as long as the diplexors are only on the lines going to SD units, that the KA issue won't be a problem.

~Alan

Alan,
I've got the following setup in my attic, and it's working well for me:

CM 4228 UHF antenna and a UHF dipole connected to a splitter (used in reverse as a combiner) with the output going into the UHF input of a Channel Master 7777 preamp. (The 4228 is aimed south for WCTV-DT and the dipole is cut for channel 17 - WALB-DT and oriented NE/SW to receive that signal) There is only about a foot of RG-6 between the balun of the 4228 and the combiner and between the dipole and the combiner.

I have a VHF dipole feeding the VHF input of the 7777 preamp. This is oriented to receive WFXL-DT.

I would be interested in knowing more how you did this. Starting this Summer, I'm going to have a lot more channel choices as both the Columbus and Tallahassee DMA will be going full-power, and I'd like to be able to receive as MANY of these channels as possible. If you have a digital camera, could you take some pictures and E-Mail them to me?!

The preamp is connected via RG-6 to the preamp power supply. The power supply output feeds the antenna input of a 5x8 multiswitch with the 4 RG-6 cables from the DirecTV 3 LNB dish feeding the four satellite inputs.

As holl_ands said in a post above, DirecTV's new KA satellites that will be used to provide new nationals (most likely next year), and HD-LIL for Albany (next year) do not allow diplexors to be used in conjunction with DirecTV's lines. I don't think I will have a problem since I do not have the line to my HD-TiVo diplexed, and so far DirecTV has not announced any plans for SD programming via the KA satellites, and my HD-TiVo will most likely be switched out for DirecTV's new HR20-250 HD-DVR this Fall (if I still want to receive my HD-DNS), so I want to set it up now with less trouble later.

~Alan

I bought a Silver Sensor at Sears a couple of years ago. They had seven stocked on their shelves. Wish I'd picked up a second one at the time because they apparently don't carry them anymore.

I posted this in the Integration forum and didn't get a response.

After reading about the new DirecTV systems and the fact that they will not allow OTA signals to be diplexed, and that I will be moving my antenna outside, I've decided I need to upgrade my cabling in the family room in preparation for the new DVR's. Currently, I have only 1 cable there (installed when the house was built and it may be RG59 - I'm not sure.

The new cable will need to be run outside since there isn't any other way to go from my multiswitch, etc. in the attic down to where it needs to go on the first floor. Therefore, I would like to have 3 Quad shield RG6 (2 for sat and 1 for OTA) along with 2 cat5 or cat6 (so I can also include a phone line to the location and networking later if needed). Does anyone make bundles with 3 RG6 cables? I've searched and can't seem to locate it.

It this isn't available, is there any type of sheath material that can be used to create a bundle? Of course, the material would need to be able to stand up to outside weather. My color preference would be white. I've thought about white PVC but it doesn't hold up to sunlight well.

Any ideas?

After reading this forum I bought a SS2000 from Solid Signal. It did not work. Did not get 5 of the local HD stations. Repaced it with the cheap one put in by DTV installers. Gets all of the local HD without any issue.

Lesson learned about buying based on advice from people who use such an item in different geographic areas. The SS may be a great antenna for a different local.
Next time I am going to check to see what works for the guy around the block.

Its going to go back to Solid Signal....Though, I must say they have been very helpful so far. Lets see how they do with the return.

I am presently enjoying pristine HDTV from a rooftop antenna, a Wineguard PR-9032. I have some experience with antennas in several prior jobs, I knew what I wanted and needed, and also wanted a minimal impact to the house appearance (the wife's requirement). My site was rather difficult, the extreme South end of Silicon Valley, 49 miles from Sutro Tower and San Bruno Mountain where all the digital transmitters are located. 100' from my house is a 1100' hill which gives a wicked ghost on analog signals. I also have one SF Bay-area station, KNTV-DT, located on VHF channel 12. To add some challenge, many of the digital broadcasts are at considerably reduced power levels compared to the analog broadcasts. Finally my neighborhood has large evergreen trees and palms which would be higher than my antenna and between it and the transmitters.

I decided to start with the high-gain UHF Yagi and antenna rotator I knew I needed, and the Winegard PR-9032 had the highest specified gain. If necessary I could add a small VHF antenna for channel 12. The mount was homemade from two sections of 2X6 heart redwood, screwed to the rear side of the wood-frame chimney and painted house color. The bottom 2X6 is bolted to the rotator, the top 2X6 is bolted to a thrust bearing which is 3' above the rotator and 1' below the chimney top. A single 10-ft mast section was used which places the antenna 6 ft above the chimney top with no guy wires. The thrust bearing was used for a completely rigid mount that could be entirely concealed on the rear of the chimney, and a 3' builder's level was used to insure that the antenna was perfectly vertical. The coax runs down the chimney along with the rotator wire and a 6-guage copper ground wire. The antenna ground and the coaxial feedthough grounding block are both attached to a 1/2" X 8' copper-clad ground rod pounded within 2" of flush to the ground. (You may think you do not need a ground on an antenna located in California which seldom experiences electrical storms. However, if your house burns down an ungrounded antenna installed by a homeowner can be grounds to deny insurance coverage.)

The results are everything I expected. The stations on actual UHF channels 19-57 are all indicating 77%-93% signal strength on my MyHD tuner in my Home Theater. In practice I get all stations on two bearings which are 301 degrees and 338 degrees, and these are marked on the old analog style rotator dial (just turn it and wait a few seconds for it to swing 37 degrees). The VHF channel 12, although nominally out of the band of my UHF Yagi antenna, is received at 47%-55% signal levels. I can receive this one channel equally well at the true bearing of 301 degrees and also at 121 degrees, with the antenna pointed directly away from the transmitter. This fact tells me that my UHF Yagi is acting as a simple dipole with zero gain for this out-of-band signal, and the short (for VHF frequencies) corner reflector and forward antenna director elements are having no effect on channel 12.

There is one channel, KSMS-DT in Monterey (UHF channel 31), which I have zero reception of, it's behind that hill I mentioned, although only 14.1 miles from my house. The eighteen from Sutro Tower and San Bruno Mountain are all there, with no amplification required for the short coax run which is about 40' total.

Gary

I recently bought a Philips 50 inch plasma TV with built-in HDTV tuner for OTA reception of HD signals. This was my first venture into HD so I had much questions regarding how to get OTA HD signals. I found AVSforum most helpful regarding all my questions. However, I was told that if I live in a large city such as Los Angeles and my non-HD reception was adequate then I would not have to buy any special antenna to receive HD OTA. A coat hanger would suffice. So I hooked my new plasma to my old rabbit ear since I live in a condo complex and cannot put out an outdoor antenna. With it, I was able to pull down 4 HD signals but they were unstable. In fact, I was never able get ABC HD and a couple of the local HD stations. I had two other indoor antennae lying around and one was even amplified that I bought from Radio Shack recently. Even with the amplified one, I got no better result then my initial older rabbit ear.

I bought this plasma TV set hoping I would be able to watch "Super Bowl" HD but instead, I had to settle for a slightly doubled imaged analog "Super Bowl". After trying all three antennae in various positions in my condo and ultimately using a longer coaxial, I pulled it out unto my balcony - no difference. No better.

After reading this site and AVS forum and other reviews, I finally settled on trying Terk HDTVi, an un-amplified antenna with some skepticism since I had no luck with all my rabbit ears.

The set up was so easy. Through antennaweb.org, I found out where all Los Angeles' TV towers are and I aimed this unit in that general direction and I repeat my new plasma's channel auto-detection programming function and watched as it tallied up all the digital and non-digital channels it was now able to receive. According to antennaweb.org, I should be able to receive 31 digital channels. Well, by the end of auto-programming cycle, my TV tallied over 45 digital channels and more than 15 non-digitals. I was ecstatic, and for the first time, I was able to get ABC HD and KCOP HD and some other in the high VHF band channels that I never knew existed.

Of course each owners' result will vary from location to location but I am most amazed and pleased with this unit esp. given its very reasonable price. Try it and hopefully your get as good of result as I have. I am very happy.

I'm using a Terk indoor for OTA reception going directly to my TV. The signal I receive is very strong for several Wash, DC / Balt, MD stations. I would like to introduce a DirecTV HD DVR and do the install myself.

Can I use a splitter on the indoor antenna, running one line to the TV and one to the DVR?...or will that setup result in a weak signal for both the TV and the DVR?

Any help is appreciated. Thanks.

I recently bought a Philips 50 inch plasma TV with built-in HDTV tuner for OTA reception of HD signals. This was my first venture into HD so I had much questions regarding how to get OTA HD signals. I found AVSforum most helpful regarding all my questions. However, I was told that if I live in a large city such as Los Angeles and my non-HD reception was adequate then I would not have to buy any
........
After reading this site and AVS forum and other reviews, I finally settled on trying Terk HDTVi, an un-amplified antenna with some skepticism since I had no luck with all my rabbit ears.

.........
Of course each owners' result will vary from location to location but I am most amazed and pleased with this unit esp. given its very reasonable price. Try it and hopefully your get as good of result as I have. I am very happy. Thank you for sharing your experience. I tried most of antennas I could buy in Radioshack, however wasn't satisfied with result. I live very close to SF and no buildings or mountains between. Unfortunately, mentioned antenna wasn't in stock in my local CC, so I tried another amplified Terk. It was much worse than the cheapest I bought from RS. I've ordered mentioned Terk and will give it a try, then I'll share my experience too.

( However, if your house burns down an ungrounded antenna installed by a homeowner can be grounds to deny insurance coverage.)
Gary


Horses##t! :D

Edited to add: this is probably not the right place to post this. I was up most of the night wrestling with this and I'm tired. I'll move it later.

I have a bunch of digital UHF stations (31,33,35 [very very strong],55) and a VHF (12) all north, and a very strong VHF (10) to the west. An un-amplified CM4228 8 bay bowtie UHF pointed north gets all of these, VHF included, quite well to my DirecTV/Tivo 250 HD receiver.

There is also one UHF (39) to the southwest that reads virtually not at all on the signal quality meter of the receiver. I cannot re-point the rooftop 4228 to get 39 without losing a couple of the others. But I can get that 39 with a simple UHF loop antenna very well at a window near the receiver. Sounds like my solution should be easy, but I can't make it work.

When I run RG-6 from the UHF loop through a coupler (I have tried 5 different types) to the receiver, 39 comes in fine. I can even orient the loop so there is very little quality signal on _any_ of the other channels. When I run a line from the rooftop through the coupler to the receiver I get all the others. But when I plug them both into the coupler at the same time, 39 disappears. There is also some slight attenuation of the others but that's no problem.

Why don't the lines combine?

A switch won't work because the Tivo is frequently recording from 39 at the same time it's recording from the other direction. If I amplify the loop antenna (with a CM7777) I get 39 OK but I lose 2 or 3 of the stations from the 4228. Interference. Overload. Voodoo.

I have tried a number of rooftop solutions with a mast mounted coupler and a small UHF antenna pointed SW. That works a lot better, 39 is no longer a problem, but no matter what I have tried with preamps and coupler combinations I can't get everything at the same time. The best combo gets me everything but 55 (though some stations read right at threshold); 55 is in and out. I have a CM Join-tenna tuned for 39 on order and possibly this might clean up the rooftop solution, which is very close to working.

But the loop antenna approach seems conceptually so simple: the 4228 gives me all but 39 perfectly; the loop gives me 39 perfectly. How can I make this work? Probably I've got interference, overload, where do I start? Attenuate 35 because it's overloading? I can do that with a Winegard tunable trap I suppose. The CM Join-tenna (tuned to 39) for the loop (that doesn't seem like it would help)? Do something about 10 because it's probably both overloading and bouncing all over the place? I don't know exactly how to deal with a digital VHF signal.

Worst nighmare of all: is this some kind of anomaly specific to my receiver? I have no other HD receiver of any kind to test that out.

I've been working on this off and on for a couple of weeks and reading all I can find. I read reports from people doing what seems to be exactly what I am doing and they say it works fine. Help appreciated.