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Google™ Search AVS: |
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06-07-05, 03:06 AM
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#2 | Link |
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AVS Special Member
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Well I saw Antennas Direct banner ad here, led me to add a few more excellent antennas...
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Free killer apps for your HTPC... (contributing AVS thread) Antennas, rotators, boosters/preamps... for wide-band VHF/UHF (contributing AVS thread) |
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06-07-05, 05:06 AM
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#3 | Link |
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MS-Comm Engineer
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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/showt...32#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...tml?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/confe...ns/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/showt...65#post5399965 |
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06-07-05, 06:03 AM
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#4 | Link |
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AVS Special Member
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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...
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Free killer apps for your HTPC... (contributing AVS thread) Antennas, rotators, boosters/preamps... for wide-band VHF/UHF (contributing AVS thread) |
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06-07-05, 05:34 PM
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#5 | Link | |
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MS-Comm Engineer
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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 |
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06-07-05, 06:33 PM
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#6 | Link |
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AVS Special Member
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Thanks again holl_ands!
I'll try to get these links @ bottom more in a relative grouping to keep them better organized...
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Free killer apps for your HTPC... (contributing AVS thread) Antennas, rotators, boosters/preamps... for wide-band VHF/UHF (contributing AVS thread) |
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06-08-05, 03:44 AM
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#7 | Link |
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MS-Comm Engineer
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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...tml?1118216319 |
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06-08-05, 06:15 AM
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#8 | Link |
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AVS Special Member
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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 Digital Topo Maps USGS Maps TopoZone Wasn't surfing long, so there must be other good ones. 1st link worked just fine for me. 
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Free killer apps for your HTPC... (contributing AVS thread) Antennas, rotators, boosters/preamps... for wide-band VHF/UHF (contributing AVS thread) |
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06-08-05, 06:58 PM
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#9 | Link |
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MS-Comm Engineer
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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...tml?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??? |
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06-08-05, 07:07 PM
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#10 | Link | |
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MS-Comm Engineer
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Satellite Pointing Angle for different satellites:
http://www.nerosoft.com/SatCalcView.asp Last edited by holl_ands; 06-08-05 at 07:18 PM.. |
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06-08-05, 09:13 PM
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#11 | Link |
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AVS Special Member
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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
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Free killer apps for your HTPC... (contributing AVS thread) Antennas, rotators, boosters/preamps... for wide-band VHF/UHF (contributing AVS thread) |
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06-09-05, 12:04 PM
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#12 | Link |
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AVS Special Member
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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 (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: =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 or NSG COMPUTATION OF GEOID03 GEOID HEIGHT. 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 6/9/05 Mean Sea Level, GPS, and the Geoid 6/9/05 The Ellipsoid! Or is it the Spheroid? How About Geoid? 6/9/05 Mathworld - Equation 22, finding earth radius @ latitude (for oblate ellipsoid) 6/9/05 The NGS GEOID Page - +/- adjustments for earth's oblate ellipse 6/9/05 NSG COMPUTATION OF USGG2003 GRAVIMETRIC GEOID HEIGHT 6/9/05 NSG COMPUTATION OF GEOID03 GEOID HEIGHT 6/9/05 Earth - ellipse demo 6/9/05 The Earth's Geoid 6/9/05 Earth - parametric latitude, WSG84 spheroid specs... 6/9/05 The Earth as an Ellipsoid, flattening Datum history... 6/9/05
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Free killer apps for your HTPC... (contributing AVS thread) Antennas, rotators, boosters/preamps... for wide-band VHF/UHF (contributing AVS thread) Last edited by RayL Jr.; 06-16-05 at 01:18 PM.. |
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06-09-05, 03:41 PM
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#13 | Link |
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MS-Comm Engineer
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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/ Last edited by holl_ands; 06-09-05 at 04:22 PM.. |
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06-09-05, 09:33 PM
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#14 | Link |
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AVS Special Member
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Again, thanks holl_ands!
 Just put all those other links in, for now just have some hyperlinks to fill out under Accessories...
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Free killer apps for your HTPC... (contributing AVS thread) Antennas, rotators, boosters/preamps... for wide-band VHF/UHF (contributing AVS thread) |
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06-09-05, 11:53 PM
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#16 | Link |
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AVS Special Member
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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) Antenna - K-Factor & climate effects
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Free killer apps for your HTPC... (contributing AVS thread) Antennas, rotators, boosters/preamps... for wide-band VHF/UHF (contributing AVS thread) |
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06-10-05, 12:13 AM
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#17 | Link | |
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AVS Special Member
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Quote:
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Free killer apps for your HTPC... (contributing AVS thread) Antennas, rotators, boosters/preamps... for wide-band VHF/UHF (contributing AVS thread) |
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06-11-05, 03:58 AM
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#18 | Link |
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AVS Special Member
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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.)
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Chris “It’s [expletive] lame to watch Jaws—a film that uses the 2.40 ratio as well as any ever produced—in the wrong format on HBO.” -Steven Soderbergh, Oscar-winning director |
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06-11-05, 04:31 AM
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#19 | Link |
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AVS Special Member
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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...
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Free killer apps for your HTPC... (contributing AVS thread) Antennas, rotators, boosters/preamps... for wide-band VHF/UHF (contributing AVS thread) Last edited by RayL Jr.; 06-11-05 at 10:30 AM.. |
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06-14-05, 01:12 PM
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#20 | Link |
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AVS Special Member
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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 6/12/05 Vincenty's Formulae, Inverse Method 6/14/05 Forward Inverse - Azimuth, distance... ellipsoidal calc program 6/14/05 Ellipsoid Radii Calculator 6/14/05 Vincenty Ellipsoid corrected “Great Circle Calculator” 6/14/05 Distance and bearig between two Latitude/Longitude points 6/14/05 Freeware DOS program calculates ellipsoidal geodesic path 6/14/05
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Free killer apps for your HTPC... (contributing AVS thread) Antennas, rotators, boosters/preamps... for wide-band VHF/UHF (contributing AVS thread) Last edited by RayL Jr.; 06-17-05 at 07:05 AM.. |
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06-17-05, 07:08 AM
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#21 | Link |
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AVS Special Member
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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).
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Free killer apps for your HTPC... (contributing AVS thread) Antennas, rotators, boosters/preamps... for wide-band VHF/UHF (contributing AVS thread) Last edited by RayL Jr.; 06-17-05 at 07:42 AM.. |
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06-27-05, 02:54 PM
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#22 | Link | |
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AVS Special Member
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Quote:
I would like to point out the Winegard PR-9032 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. |
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06-27-05, 11:54 PM
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#23 | Link |
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AVS Special Member
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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
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Free killer apps for your HTPC... (contributing AVS thread) Antennas, rotators, boosters/preamps... for wide-band VHF/UHF (contributing AVS thread) |
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06-28-05, 10:15 PM
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#24 | Link |
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AVS Special Member
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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 (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) 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?
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Free killer apps for your HTPC... (contributing AVS thread) Antennas, rotators, boosters/preamps... for wide-band VHF/UHF (contributing AVS thread) |
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06-29-05, 09:04 PM
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#25 | Link | |
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AVS Special Member
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Quote:
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 TV channel signal level meter and analyzer and a Hewlett-Packard spectrum analyzer to test with. 73's WA5RMP Last edited by Wendell R. Breland; 06-29-05 at 10:44 PM.. |
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06-30-05, 06:42 PM
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#27 | Link |
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MS-Comm Engineer
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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/test...21cd_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 |
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07-09-05, 02:52 PM
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#29 | Link |
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AVS Special Member
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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. |
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07-09-05, 04:49 PM
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#30 | Link | |
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AVS Special Member
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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...
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Free killer apps for your HTPC... (contributing AVS thread) Antennas, rotators, boosters/preamps... for wide-band VHF/UHF (contributing AVS thread) |
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Antennas, rotators, boosters/preamps... for wide-band VHF/UHF
