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post #4801 of 4829 Old 08-04-2014, 09:40 PM
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Can any of you home antenna builders help me on how to build an antenna tuned into UHF-LP 30 (My local 'RetroTV' station is KSMI-LD 30.1-6) as they are now showing classic "DR WHO" and I am currently only receiving a signal strength of 35% while my major networks are in the 95+% range from the same 'broadcast tower farm'.
So I am looking for a 'tuned' antenna that I can add the feed to my current antenna with out the loss of signals on the adjacent channels.
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post #4802 of 4829 Old 08-04-2014, 10:36 PM
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We need more info to narrow the scope of your inquiry. What Antenna are you using now? Indoor? Outdoor? Pointed towards KSMI or another direction to favor some other station? And we need your TVFool Report (enter location and copy/paste the Results URL (webaddress at top of page) into a post so we can see your relative signal strengths.
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post #4803 of 4829 Old 08-05-2014, 10:43 PM
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Quote:
Originally Posted by holl_ands View Post
We need more info to narrow the scope of your inquiry. What Antenna are you using now? Indoor? Outdoor? Pointed towards KSMI or another direction to favor some other station? And we need your TVFool Report (enter location and copy/paste the Results URL (webaddress at top of page) into a post so we can see your relative signal strengths.
I hope that this answers your questions you posed to me.

?: What Antenna are you using now?
A: Radio Shack External/Outdoor Antenna When Purchased in 1995 was rated at 70 miles VHF it is about 6 foot long tip to tip.

?: Pointed towards KSMI or another direction to favor some other station?
A: No "most" of the local stations have their towers in a "Tower Farm" in a little suburb of named 'Colwich, KS' which is where it is pointing.

TV Fool: http://www.tvfool.com/?option=com_wr...e1c61f0803753f
Note: TV Fool still lists the station with a call number of 50.1-6 when they have changed to match their UHF channel of 30.1-6
http://en.wikipedia.org/wiki/KSMI-LD

If anything the antenna is pointing towards KTPS8.1-4
KPTS-DT (Digital)
Channel: 8 (8.1)
Network: PBS
Maximum ERP: 32.000 kW
Coordinates: 38.055845 -97.776715
Effective ERP: 17.104 kW (Adjusted according to your location)
Distance: 39.2 miles Azimuth: 320 degrees Compass: 317 degrees

Transmitter Profile Detail
KSMI-LP (Digital)
Channel: 30 (30.1)
Network:
Maximum ERP: 15.000 kW
Coordinates: 37.800289 -97.525046
Effective ERP: 15.000 kW (Adjusted according to your location)
Distance: 16.8 miles Azimuth: 318 degrees Compass: 314 degrees

So the difference is only about 2 degrees which is such a small amount when trying to adjust an antenna.
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post #4804 of 4829 Old 08-06-2014, 08:25 AM
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Your TV Fool report shows it should be easy to receive all the LOS stations in your list by pointing the antenna at about 335 degrees. It doesn't get much better than that. If you're having problems with one or more stations I'd check the antenna and cabling. Maybe something happened in the last 19 years. You show your antenna mounted at only 10'. Is it outside on the roof? If not, it needs to be.
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post #4805 of 4829 Old 08-06-2014, 11:05 AM
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Simple question: How big must the wire be to hook up UHF antenna elements?

I am building an indoor UHF antenna and have several elements to my antenna (2 to 14 figure-eight full wave elements). I know I need to hook them together in parallel but how small of a wire can I use?
Since there is very little voltage or current can I use 22 gauge? Or, is 18 gauge needed for some reason? How big of a wire do I need to get all the signal out of my elements?
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post #4806 of 4829 Old 08-06-2014, 10:10 PM
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Feedlines are Transmission Lines which need to have a specific Impedance to prevent SWR problems that degrades both the signal strength AND the digital waveform due to signals reflecting up and down the coax. The Wire Size and Separation between the Feedlines determines this Impedance. If Wire Size is TOO small, there will also be unacceptable (RF) ohmic losses. Typically AWG12 and preferably AWG10 is used for Feedlines at VHF and UHF frequencies.

All "Figure-Eights" in Parallel won't work...Impedance will be way too low, resulting in high SWR. You can't JUST hook up some individual antennas and hope for the best...they have to be carefully laid out in an Array (Vertical, Horizontal...or a mixture) and interconnected with the correct LENGTH of Feedlines, such as is shown for the following COMPUTER OPTIMIZED 8-Bay Bowtie designs:
http://imageevent.com/holl_ands/stac...oubleanglerefl
http://imageevent.com/holl_ands/stac...5x9noreflector
http://imageevent.com/holl_ands/multibay/8bayrefl
http://imageevent.com/holl_ands/multibay/8bay

Perhaps you can provide more detailed information on what you're working on.....BTW: I analyzed individual Figure-8 Antennas here:
http://imageevent.com/holl_ands/loops/twinhoopchireix
http://imageevent.com/holl_ands/loops/hivhftwinloops
Note that QICT (Quarter Inch Copper Tubing) Elements provided acceptable SWR, whereas AWG10 did NOT...this is fairly common for Loop Antennas....except the similar Hourglass-Loop designs are fairly insensitive to Element Wire Size.
http://imageevent.com/holl_ands/loops

There are also "Figure-8" Antennas where there is NO interconnection at the crossover point, such as:
http://pa0fri.home.xs4all.nl/Ant/Magloop/magn8.htm
http://www.mixw.co.uk/MagLoop/magloop.htm

Ken Nist has (had?) an EZNEC model for the above "Figure-8" Antenna on his HDTVPrimer website, which I converted into the fol. 4nec2 File. It provides 2.7 to 5.4 dBi Raw Gain with good SWR, EXCEPT below 554 MHz it climbs to an excessive value of 5.5:

Code:
  Freq  RawGain  NetGain    SWR    BeamWidth
=========================================
 470.0    2.683   -0.515   6.191    83.5
 482.0    2.963    0.140   5.479    83.5
 494.0    3.223    0.769   4.831    83.5
 506.0    3.463    1.367   4.245    83.5
 518.0    3.703    1.950   3.720    83.3
 530.0    3.913    2.483   3.252    83.3
 542.0    4.123    2.992   2.837    83.2
 554.0    4.317    3.457   2.471    83.2
 566.0    4.507    3.885   2.151    82.9
 578.0    4.677    4.256   1.873    82.8
 590.0    4.837    4.577   1.635    82.7
 602.0    4.987    4.846   1.435    82.5
 614.0    5.117    5.052   1.277    82.4
 626.0    5.227    5.195   1.185    82.2
 638.0    5.316    5.278   1.207    82.1
 650.0    5.376    5.294   1.317    82.0
 662.0    5.406    5.250   1.464    81.8
 674.0    5.396    5.142   1.627    81.6
 686.0    5.316    4.950   1.796    81.6
 698.0    5.176    4.694   1.959    81.3
 710.0    4.946    4.358   2.106    81.2
 722.0    4.612    3.937   2.222    81.1
 734.0    4.162    3.433   2.296    80.8
 746.0    3.572    2.827   2.317    80.7
 758.0    2.842    2.122   2.284    80.6
 770.0    1.972    1.314   2.199    80.4
 782.0    0.992    0.426   2.075    79.9
 794.0   -0.068   -0.526   1.926    79.1
 806.0   -1.148   -1.497   1.769    78.1
Code:
CM Figure-8 Loop, Ken Nist's EZNEC file converted with 4nec2 on 28-Oct-11 15:21
CE
GW    1    5    -0.217239    -0.563649    3.196611    -0.217239    0.5636488    3.196611    0.04
GW    2    5    -0.217239    0.5636488    3.196611    -0.217239    1.622963    2.8110524    0.04
GW    3    5    -0.2172387    1.62296299    2.81105236    0    2.48652087    2.08644134    0.04
GW    4    5    0    2.48652087    2.08644134    0    3.05017165    1.11016772    0.04
GW    5    5    0    3.05017165    1.11016772    0    3.24592598    -7.9361e-6    0.04
GW    6    5    0    3.24592598    -7.9361e-6    0    3.05012756    -1.1101752    0.04
GW    7    5    0    3.05012756    -1.1101752    0    2.48647992    -2.0864417    0.04
GW    8    5    0    2.48647992    -2.0864417    0    1.62292008    -2.8110535    0.04
GW    9    5    0    1.62292008    -2.8110535    0    0.56364882    -3.1966098    0.04
GW    10    5    0    0.56364882    -3.1966098    0    -0.5636488    -3.1966098    0.04
GW    11    5    0.2172387    -0.563649    3.196611    0.2172387    -1.62296    2.8110524    0.04
GW    12    5    0.2172387    -1.6229602    2.81105236    0    -2.486526    2.08644134    0.04
GW    13    5    0    -2.486526    2.08644134    0    -3.0501752    1.11016772    0.04
GW    14    5    0    -3.0501752    1.11016772    0    -3.2459307    -7.9361e-6    0.04
GW    15    5    0    -3.2459307    -7.9361e-6    0    -3.0501303    -1.1101752    0.04
GW    16    5    0    -3.0501303    -1.1101752    0    -2.4864803    -2.0864417    0.04
GW    17    5    0    -2.4864803    -2.0864417    0    -1.622926    -2.8110535    0.04
GW    18    5    0    -1.622926    -2.8110535    0    -0.5636488    -3.1966098    0.04
GW    19    5    0    -0.5636488    9.58984646    0    0.56364882    9.58984646    0.04
GW    20    5    0    0.56364882    9.58984646    0    1.62296299    9.20428346    0.04
GW    21    5    0    1.62296299    9.20428346    0    2.48652087    8.47967323    0.04
GW    22    5    0    2.48652087    8.47967323    0    3.05017165    7.50339764    0.04
GW    23    5    0    3.05017165    7.50339764    0    3.24592598    6.39322047    0.04
GW    24    5    0    3.24592598    6.39322047    0    3.05012756    5.28305512    0.04
GW    25    5    0    3.05012756    5.28305512    0    2.48647992    4.3067874    0.04
GW    26    5    0    2.48647992    4.3067874    0.2172387    1.62292008    3.58217638    0.04
GW    27    5    0.2172387    1.6229201    3.5821764    0.2172387    0.5636488    3.196611    0.04
GW    28    5    0.2172387    0.5636488    3.196611    0.2172387    -0.563649    3.196611    0.04
GW    29    5    0    -0.5636488    9.58984646    0    -1.6229602    9.20428346    0.04
GW    30    5    0    -1.6229602    9.20428346    0    -2.486526    8.47967323    0.04
GW    31    5    0    -2.486526    8.47967323    0    -3.0501752    7.50339764    0.04
GW    32    5    0    -3.0501752    7.50339764    0    -3.2459307    6.39322047    0.04
GW    33    5    0    -3.2459307    6.39322047    0    -3.0501303    5.28305512    0.04
GW    34    5    0    -3.0501303    5.28305512    0    -2.4864803    4.3067874    0.04
GW    35    5    0    -2.4864803    4.3067874    -0.2172387    -1.622926    3.58217638    0.04
GW    36    5    -0.217239    -1.622926    3.5821764    -0.217239    -0.563649    3.196611    0.04
GS    0    0    0.0254        ' All in inches.
GE    0
GN    -1
LD    5    0    0    0    5.74713e7    0
EX    0    10    3    0    -1    1.22461e-16
'
' FR Freq Sweep choices in order of increasing calculation time (fm holl_ands):
' FR 0 0 0 0 590 0        ' Fixed Freq
FR 0 29 0 0 470 12        ' Freq Sweep 470-806 every 12 MHz - OLD UHF BAND
' FR 0 39 0 0 470 6        ' Freq Sweep 470-698 every 6 MHz - PREFERRED FOR UHF
' FR 0 77 0 0 470 3        ' Freq Sweep 470-698 every 3 MHz
' FR 0 153 0 0 470 1.5        ' Freq Sweep 470-698 every 1.5 MHz
' FR 0 71 0 0 300 10        ' Freq Sweep 300-1000 every 10 MHz - WIDEBAND SWEEP
' FR Hi-VHF choices:
' FR 0 15 0 0 174 3        ' Freq Sweep 174-216 every 3 MHz
' FR 0 29 0 0 174 1.5        ' Freq Sweep 174-216 every 1.5 MHz - PREFERRED
' FR 0 43 0 0 174 1        ' Freq Sweep 174-216 every 1 MHz - Hi-Rez
' FR 0 26 0 0 150 6        ' Freq Sweep 150-300 every 6 MHz - WIDEBAND SWEEP
' FR 0 64 0 0 54 12        ' Super Wide Freq Sweep 54-810 every 12 MHz
' RP choices in order of increasing calculation time:
' RP 0 1 1 1510 90 90 1 1 0 0        ' 1D Gain toward 0-deg Azimuth - SIDE GAIN
' RP 0 1 1 1510 90 0 1 1 0 0        ' 1D Gain toward 90-deg Azimuth - FORWARD GAIN
' RP 0 1 1 1510 90 180 1 1 0 0        ' 1D Gain toward 270-deg Azimuth - REVERSE GAIN
' RP 0 1 37 1510 90 0 1 5 0 0         ' 2D (Left only) Azimuthal Gain Slice
RP 0 1 73 1510 90 0 1 5 0 0         ' 2D Azimuthal Gain Slice - PREFERRED
' RP 0 73 1 1510 90 0 5 1 0 0         ' 2D Elevation Gain Slice
' RP 0 73 73 1510 90 0 5 5 0 0         ' 3D Lower Hemisphere reveals antenna (Fixed Freq)
' RP 0 285 73 1510 90 0 5 5 0 0        ' 3D Full Coverage obscures antenna (Fixed Freq)
EN

Last edited by holl_ands; 08-06-2014 at 10:41 PM.
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post #4807 of 4829 Old 08-06-2014, 11:03 PM
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DavidEC: Your TVFool Results indicate that you have strong signals, so your current Outdoor Antenna "should" be working just fine, esp. if weaker CBS and PBS stations work okay. I suspect you have a severe SWR mismatch problem that is only affecting KSMI (Ch30). First thing to try is to insert different lengths of fairly short pieces of Coax (1 to 6 ft) in the downlead, which "should" move the SWR Null to a different frequency (hopefully NOT affecting another station you want). Whether that works or not, it's still advisable to swap out the Balun and replace any Coax connectors that don't look secure...better yet, replace them ALL to hopefully eliminate any SWR problems. It is also possible that moisture has entered your downlead, which you can test by temporarily running a separate Coax to see if that fixes your problem....if so, you're at least ready for The Doctor.

In order to prevent a second UHF Antenna interfering with your R-S Antenna, you would need to combine them using either a C-M JoinTenna (out of production for many years) or a fairly pricy Single Channel Insertion Filter from Tin-Lee. HOWEVER, I would recommend using a UHF/VHF Combiner (aka UVSJ) to combine the VHF signals from the R-S to a new UHF Antenna, just in case there is something wrong in the R-S (or it's Balun). Since you have strong signals, you might want to start with a simple DIY UHF Hourglass-Loop or UHF Trapezoidal-Loop Antenna....perhaps start with No Reflector and add Reflector Rods or a Screen Grid if you need more:
http://imageevent.com/holl_ands/loops/uhfhourglassloop
http://imageevent.com/holl_ands/loop...dtrapezoidloop
http://imageevent.com/holl_ands/loop...zoidloop2xbars

A 4-Bay Bowtie would also be a good alternative...or your choice of a DIY Grey-Hoverman....

PS: A "Single channel" Antenna in the UHF Band is very difficult to design/build....typically they are at least THREE ADJACENT CHANNEL Antennas at -3 dB down points, with significant Gain for much more than several Channel positions above and below the desired Channel. So without external Filters, it WILL likely interfere with the Primary Antenna. For example, see Ch14-17 Yagis (which were actually Optimized for Ch14-15, but ended up being FOUR Channels wide):
http://imageevent.com/holl_ands/yagis
Blonder-Tongue UHF "Single Channel" Yagi's cover the entire New UHF Band with only five models: 6 Channels Wide for lowest channels and 11 Channels Wide for the highest channels.
Note that Intro to this webpage provides instructions for Resizing Antenna to ANY other Frequency Band.

Last edited by holl_ands; 08-06-2014 at 11:35 PM.
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post #4808 of 4829 Old 08-06-2014, 11:18 PM
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Exclamation

Quote:
Originally Posted by Calaveras View Post
Your TV Fool report shows it should be easy to receive all the LOS stations in your list by pointing the antenna at about 335 degrees. It doesn't get much better than that. If you're having problems with one or more stations I'd check the antenna and cabling. Maybe something happened in the last 19 years. You show your antenna mounted at only 10'. Is it outside on the roof? If not, it needs to be.
It should be showing at about 20' off the ground, at the peak of the roof, it is mounted on two 10' poles for grounds and wind issues did not want the antenna to rip up and off of my roof, and all the cabling was replaced less than five years ago which made a marked improvement on the full power stations.
But no improvement on the 'Low Power' stations.

One thing you can not see in FOOL is local building( neighbors two story barn) and rised highway.. which in fact means I would have to go to about 40' to get above the average tractor+trailer rig on the highway that is to the north west of my home.. but then I am into local aircraft flight space as I was informed that I can not go higher than 30' which would be equal to a two story building.

So back to my main question.. can I build a 'tuned' antenna for UHF band USA Channel "30" with rapid drop off not to interfere with channels 24 and 36 on each side?
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post #4809 of 4829 Old 08-06-2014, 11:44 PM
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Quote:
Originally Posted by DavidEC View Post
So back to my main question.. can I build a 'tuned' antenna for UHF band USA Channel "30" with rapid drop off not to interfere with channels 24 and 36 on each side?
NO.....see above explanation....even a long Corner Yagi will provide -3 dB bandwidth of about 5-6+ channels on Ch30, with significant interference at twice that bandwidth, i.e. 5-6 channels away on either side from Ch30.
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post #4810 of 4829 Old 08-07-2014, 01:03 AM
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Quote:
Originally Posted by holl_ands View Post
Perhaps you can provide more detailed information on what you're working on....
I was reading through this forum/post around page-50-60 and came across this full-wave design. Outer circle 8" and inner 5" (dual frequency). I added about a 3/4" space between the large circles per one of the suggestions (I think they used 1"). I cut them out of aluminum roof flashing and glued them on plastic corrugated board (Like cardboard but plastic) using contact cement. I have 6 of them made and another 8 already cut.
The way I understand it is that I don't have to worry about phasing because it's full wave. But I misunderstood about being in parallel. It is simply two loops in parallel I guess, they weren't talking about hooking them up in an array. So I have no idea how to hook them up in an array.

I'll see if I can pick up some some AWG-12 wire so as to prevent losses. I'm assuming it needs to be solid, not stranded.
Anyone got an idea how to make an array of them?
I know they have to be vertical as pictured.
I was thinking about 3 rows of 4 each, for a total of 12.
Any suggestions appreciated!




I tried one and it seems to work. But I'm thinking it would do much better with an array of them.



TVFool for 75078 Zip:
http://www.tvfool.com/?option=com_wr...e1c60d208094ac

Last edited by FriedOkra; 08-07-2014 at 10:53 PM.
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post #4811 of 4829 Old 08-07-2014, 01:03 AM
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Quote:
Originally Posted by DavidEC View Post
So back to my main question.. can I build a 'tuned' antenna for UHF band USA Channel "30" with rapid drop off not to interfere with channels 24 and 36 on each side?
NO.....see above explanation....even a long Yagi or Corner Yagi will provide -3 dB bandwidth of about 5-6+ channels, with significant interference at twice that bandwidth, i.e. 5-6 channels away from Ch30.

Fol. example shows the extent of the problem, Rescaling DL6WU 22-Element Long Yagi from 432 MHz (Ham Band) to 569 MHz (Ch30). [Using a FOLDED Dipole and Re-optimizing would yield a 300-ohm Antenna.] Although it is very common for Yagi's to experience a rapid frequency roll-off on the high frequencies, they typically have a fairly slow roll-off on the lower frequencies:



Technical Info re Yagi's designed per DL6WU's formulas and look-up-tables can be found here, bearing in mind that they are for 50-ohm or 200-ohm (with 4:1 Balun) Antennas typically used in the Ham Radio Bands and hence are NOT Optimum for TV Bands:
http://dpmc.unige.ch/dubus/9102-4.pdf
http://www.qsl.net/vk2kfj/DL6WU.html
DL6WU's empirically derived design charts have been embedded into numerous on-line (e.g.K7MEM) and downloadable Yagi Calculators, including (FREEWARE) YagiCAD, which I used to generate the results shown above, after selecting one of the higher Gain Examples that came with the program.

I have a Ch30 "Single Channel" Optimization running overnight for a big Corner Yagi....based on a Rescale of it's Ch14 cousin, it might not have as rapid a roll-off on the high frequencies....

Last edited by holl_ands; 08-07-2014 at 01:34 AM.
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post #4812 of 4829 Old 08-07-2014, 07:20 AM
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Quote:
Originally Posted by DavidEC View Post
It should be showing at about 20' off the ground, at the peak of the roof, it is mounted on two 10' poles for grounds and wind issues did not want the antenna to rip up and off of my roof, and all the cabling was replaced less than five years ago which made a marked improvement on the full power stations.
But no improvement on the 'Low Power' stations.

One thing you can not see in FOOL is local building( neighbors two story barn) and rised highway.. which in fact means I would have to go to about 40' to get above the average tractor+trailer rig on the highway that is to the north west of my home.. but then I am into local aircraft flight space as I was informed that I can not go higher than 30' which would be equal to a two story building.

So back to my main question.. can I build a 'tuned' antenna for UHF band USA Channel "30" with rapid drop off not to interfere with channels 24 and 36 on each side?
Your TV Fool report shows 10' off the ground.

Do you live right next to an airport? The height limit for towers is 200' without having to register the tower. I wouldn't take someone's word on 30'. Here's an FAA site about construction height near an airport:

https://oeaaa.faa.gov/oeaaa/external/portal.jsp

I agree that you're not going to be able to build a channel 30 only antenna. Even if you could more gain is not going to do anything. Almost everyone assumes that the station is too weak when it is not received. That often is not the problem and is almost certainly not your problem with KSMI which shows a Noise Margin of 46 dB. That's a huge signal! The signal is so strong that if it was running just 1.5 watts you should still receive it. You need to look elsewhere for the problem. Maybe you have a multipath issue which could be solved by getting the antenna above the local obstructions.

Without someone taking a spectrum analyzer to your home it's not possible for us to say exactly what your problem is.
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post #4813 of 4829 Old 08-08-2014, 10:53 PM
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Originally Posted by Calaveras View Post
Your TV Fool report shows 10' off the ground.

Do you live right next to an airport? The height limit for towers is 200' without having to register the tower. I wouldn't take someone's word on 30'. Here's an FAA site about construction height near an airport:

https://oeaaa.faa.gov/oeaaa/external/portal.jsp

I agree that you're not going to be able to build a channel 30 only antenna. Even if you could more gain is not going to do anything. Almost everyone assumes that the station is too weak when it is not received. That often is not the problem and is almost certainly not your problem with KSMI which shows a Noise Margin of 46 dB. That's a huge signal! The signal is so strong that if it was running just 1.5 watts you should still receive it. You need to look elsewhere for the problem. Maybe you have a multipath issue which could be solved by getting the antenna above the local obstructions.

Without someone taking a spectrum analyzer to your home it's not possible for us to say exactly what your problem is.
While I don't live next to an airport.. I do live in a major military flight line, during the day time there is a flight over head almost every 30 minutes, luckily the flights stop when the sun goes down till about an hour after sun rise..

I do want to thank everybody that replied!

But on another note I guess that I only have one choice and that is install a new antenna set-up, and at the same time add another 10' to my current pole and guide wires to brace for the Kansas winds.

Any suggestions of a low cost: high VHF / UHF outdoor antenna, pre-amp, & five point (minimum, seven point would be ideal) distribution amp? : this way I will be replacing all current off air signal capturing hardware.

Before the local cable system went fiber/digital my current set up could pick up most all unscrambled cable channels.. by pointing the antenna directly at the cable/power lines straight north ..which in a way was a pain in the "B" due to ghosting/multiplexed signals in the VHF bands.
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post #4814 of 4829 Old 08-09-2014, 07:39 AM
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David,

Your highest strength channel (adjacent 31) is at 64 db nm, and transmitting from the same tower as ksmi.

I don't know what tuner you have, but the best chance of picking up ksmi is to try out different tv tuners which may possibly be able to lock onto the ksmi channels. The chances of a lock are slim to none, but worth a try.

Wish u good luck
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post #4815 of 4829 Old 08-10-2014, 02:07 PM
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"SINGLE CHANNEL" 18-EL YAGI with 14 RR CORNER REFLECTOR:

I uploaded 4nec2 Results for 18-Element Yagi with 14 Reflector Rods in a Corner Reflector:
http://imageevent.com/holl_ands/yagi...i14rrcorneropt

Optimized for Ch30 (18.6 dBi on 566-572 MHz), the actual -3 dB Bandwidth is 50 MHz (540-590 MHz), which results in negligible reduction on Ch27 (17.8 dBi on 554 MHz Upper Band Edge) and Ch33 (16.8 dBi on 584 MHz Lower Band Edge).

I investigated Quarter-Wave Notch Filters awhile back, but they aren't going to be of much use, since the -10 dB Notch only had a Bandwidth of about 1 MHz (we need 6 MHz to Notch out each Channel) and ultimately 15 to 20 dB reduction is needed to reduce "co-channel interference" from the Yagi into the primary Antenna....which would require TWO Notch Filters for each of TWO Channel positions...and good luck getting it all to work, cuz they interact and the dimensions are VERY CRITICAL. So Tin-Lee Filters would be the only viable alternative.
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post #4816 of 4829 Old 08-10-2014, 03:54 PM
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Can a notch filter do anything for the below readings (20 foot antenna height)?

KSMI ch 30.1 nm: 45.8 sig power: -45.1
KDCU ch 31.1 nm: 64.0 sig power: -26.9
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post #4817 of 4829 Old 08-10-2014, 05:40 PM
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NO WAY: Quarter-Wave Notch only provided 10 dB Attenuation across 1 MHz...you would need to very carefully tweak SIX of them (and they interact with each other) to attenuate a typical 6 MHz DTV signal.....and if it's an ADJACENT signal, it's also going to seriously degrade Gain and SWR on the desired channel.

What CAN be done (if the geometry permits) is to use a pair of matching Horizontally Stacked Antennas to steer a NULL directly FORWARD towards the undesired direction and a BEAM(s) in the desired direction(s):
http://www.hdtvprimer.com/antennas/ganging.html
http://imageevent.com/holl_ands/stac...hackednullbeam


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post #4818 of 4829 Old 08-10-2014, 07:03 PM
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I just started reading this thread. Interesting. Why do you guys build your antenna's instead of just buying one?

Hope I didn't offend anyone by butting in.

This may be something for me to try someday.

(LCD - Sony KDL - XBR4) (Receiver - Sony STR-DA4ES)(Blu Ray - Oppo BDP-83) (PS3)( Dish Hopper DVR With Sling) Speakers (L & R - Paradigm Studio 20) (Center -Paradigm CC-470) (Surrounds & Back Surrounds - Paradigm SA-15R in walls) (Subwoofer 1 - Sunfire HRS-12) (Subwoofer 2 - Paradigm PW-2100)
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post #4819 of 4829 Old 08-10-2014, 08:43 PM
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Holl, 6 notch filters for one channel? dang


SkyTrooper, no worries, ask away anytime. I can't be of much help tho, but Holl_ands sure can answer any questions you may have.

One thing I do know, is that the antenna's they design maximize gains for the latest tv frequency range, and also custom tuned antenna's can be designed to help bring in problematic channels.

Browse Holl_ands antenna modeling simulations here --> http://imageevent.com/holl_ands
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post #4820 of 4829 Old 08-12-2014, 09:59 AM
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Thanks Don H. After I went to the link you provided, basically people are buying a antenna and modifying it to their needs. I also see the use of filters.

(LCD - Sony KDL - XBR4) (Receiver - Sony STR-DA4ES)(Blu Ray - Oppo BDP-83) (PS3)( Dish Hopper DVR With Sling) Speakers (L & R - Paradigm Studio 20) (Center -Paradigm CC-470) (Surrounds & Back Surrounds - Paradigm SA-15R in walls) (Subwoofer 1 - Sunfire HRS-12) (Subwoofer 2 - Paradigm PW-2100)
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post #4821 of 4829 Old 08-12-2014, 09:06 PM
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It's amazing stuff, and much of it is over my head. Yes, you'll see simulations/comparisons of existing antenna's, and also much improved upon designs, plus a lot of new custom creations.

Filters? Are you referring to lc filters? For the designs I've been looking at on Holl's site, I don't recall seeing any filters, but I have used them long ago to tune in my antenna's (mostly to compensate for my errors). Pc's and antenna software weren't around then, and it was all trial and error if you tried to modify existing designs w/out all the fancy analyzers.
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post #4822 of 4829 Old 08-12-2014, 10:08 PM
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Quote:
Originally Posted by Don_H View Post
Can a notch filter do anything for the below readings (20 foot antenna height)?

KSMI ch 30.1 nm: 45.8 sig power: -45.1
KDCU ch 31.1 nm: 64.0 sig power: -26.9

If the signal strength of the two stations are anywhere near what TV Fool predicts you should have no trouble decoding KSMI. It is only 18 dB weaker.

I've attached a couple of spectrum analyzer images of station situations I have here. The first images shows KTLN on 47 sandwiched in between KQCA on 46 and KSPX on 48. KTLN is about 20 db weaker than KQCA and 30 dB weaker than KSPX. I never have any trouble decoding KTLN as longer as it doesn't drop below the minimum strength that can be decoded.

The second image shows KUVS on 18 next to KOFY on 19. KOFY is hard to decode because of adjacent channel interference from KUVS which is 40 dB stronger. You might think that a very sharp notch filter on KUVS would eliminate the problem. It wouldn't. Notice that on the low side of KUVS you see the signal trail off into the top end of 17 starting at 40 dB down. That same amount of signal is present on the high side trailing off into 19. That destroys the SNR at the low end of KOFY making it impossible to decode. Even if you had a perfect channel 18 notch filter it wouldn't get rid of the signal that bleeds into the adjacent channels.
Attached Images
File Type: gif KTLN.gif (23.5 KB, 7 views)
File Type: gif KUVS_KOFY_annotated.gif (23.3 KB, 5 views)
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post #4823 of 4829 Old 08-12-2014, 11:06 PM
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Hi Cal,

Nice! I could spend days testing, playing, and learning with that frequency analyzer!

Thanks for the info, unfortunately for me, my signal levels are low. I'm 70 miles away in Salina, so I wouldn't have a chance of receiving ksmi, although I have no problem receiving kdcu at 100%, and kmtw at ~80% from atop Indian Rock Park. I didn't even see a hint of ksmi though. Adjacent 31 must be killin' it.

Looks like DavidEC may stand a chance of getting what he wants. Dave, let us know if those filters work for you.
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post #4824 of 4829 Old 08-13-2014, 11:55 PM
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Good evening everyone. After several years of inactivity I find reason to reactivate and cruise back through here. Long story short, my girlfriend is having major difficulties getting any sort of UHF reception in her current apartment. With football season upon us, this is cause for major concern. As an upcoming weekend project we decided it would be fun to try building an UHF antenna rather than buying yet another off the shelf model and almost invariably returning it for ineffectiveness. I'm looking for suggestions of which kind to try building; having read through a half dozen plans and designs a little expert guidance in the right direction wouldn't hurt.

Presently we both live in the flat part of California and are only about a mile and half apart. While my place is surrounded by groves of large trees, there are no buildings over one story between myself and most of the transmission towers about 20 miles away to the NW. In my case, a directional antenna pointed WSW picks those up just fine along with VHF & UHF channels broadcast from even further away to the west. Her place, however, is on the first floor of a two-story building, and her line of sight to the important towers 20 miles to the NW is blocked by several two+ story commercial buildings just across the street. We've tried several omnidirectional antennas from various stores without much success. They find VHF channels, but no UHF. Signal amps/boosters help some with VHF strength but aren't helping with UHF. I've taken my antenna over and spent a few hours searching the sky only to find it performs even worse than the omnidirectional antennas in her location.

All this has led me to believe she needs something fairly sizable and omnidirectional. What type I'm not quite sure. It does need to be indoor, however, for practical reasons. We can set it up to face most of the towers to the NW through a sliding glass door to help minimize interference. Here's the TVFool report for good measure. KCRA, KOVR, and KTXL are the key channels. With that, any suggestions?
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post #4825 of 4829 Old 08-14-2014, 03:50 AM
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Quote:
Originally Posted by ;
Her place, however, is on the first floor of a two-story building, and her line of sight to the important towers 20 miles to the NW is blocked by several two+ story commercial buildings just across the street.
You're probably tilting at a windmill The UHF signals are likely getting blocked by the buildings and simply aren't making it to or into her apartment. Watch the games at your place.

Omni antennas are the poorest possible choice. A very directional antenna would offer the best hope for such an impaired location.
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post #4826 of 4829 Old 08-14-2014, 02:15 PM
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A few suggestions to consider, listed in increasing SIZE and complexity. You might want to start with a NO Reflector version...you might get lucky...and if not add one of the various Reflector Options:

UHF Hourglass, which only requires stringing some Wire (size not very important) on a DIY Frame or Metal/Aluminized Tape on Cardboard:
http://imageevent.com/holl_ands/loops/uhfhourglassloop

UHF Quad-Trapezoid enhancement to Hourglass:
http://imageevent.com/holl_ands/loop...dtrapezoidloop

UHF FF4 or M4 4-Bay Bowtie, may use AWG12, AWG10 or Metal/Aluminized Tape on Cardboard:
http://imageevent.com/holl_ands/multibay/4bay
http://imageevent.com/holl_ands/multibay/4bayrefl
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post #4827 of 4829 Old 08-14-2014, 02:47 PM
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Watching the games with her is the fallback option in case nothing seems to work. It will be plenty of fun until we want to watch different games on one TV. Until then it's simply a fun challenge to see if we can make something work. I know there are some UHF signals bouncing around in there, as we've picked up some before by aiming indoor antennas in odd locations (e.g. right angle to the distant towers, off at the ground, etc.). Only a few minutes ago it dawned on me her exterior is stucco, and usually that means metal grids. That should mean a fair shot at improvement just by positioning the antenna by her sliding glass door, which also happens to face NW towards the desired towers.

In regards to specific antennas:
  • I have some old, spare antennas leftover from previous wireless base stations (the joys of working IT), these are worth a shot, I'm assuming?
  • On the UHF hourglass loop, the center strands are just leads to the coax connector, correct?
  • On the UHF quad-trapezoid loop, are the top and bottom connected or is there supposed to be a gap there? The diagrams show a small gap and it's not clear if that's intentional.
  • Would reception on a bowtie be degraded significantly by enclosing it in canvas, fabric, or something else? When discussing this last weekend the estrogen took over and she started thinking about how to conceal antennas with fabric enclosures, or maybe even a canvas painting over a wood frame that would enclose the antenna. Overall she was most impressed with a bowtie design, even though it rankles her aesthetic sense.
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post #4828 of 4829 Old 08-14-2014, 03:42 PM
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Stucco is a killer due to the chicken-wire behind it.

Low-E glass is a killer, clear glass isn't, so check the slider.

WiFi equipment and stuff is useless, wrong frequency.

Fabric and the like is transparent to RF energy, so she can decorate away to her heart's content.
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post #4829 of 4829 Old 08-14-2014, 06:31 PM
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Small GAP at the top and bottom of the Quad-Trapezoid Antenna provides significantly MORE Gain than if they were connected together....and since the Gain drops as the GAP is increased, I assumed it would be only about 1/4-in wide, the smallest that I think can be fabricated without inadvertently touching. If desired a NON-Conductive material can be used to interconnect and hence maintain the Gap.

The Center Wire (marked with a Red Circle) represents where the two wires of a (300-to-75-ohm) Balun Transformer need to be connected and is the SAME for all three Antenna types. The output of the Balun is a 75-ohm Coax Connector that goes to the HDTV's input.

Fol. diagram explicitly shows the Balun connections:
http://rickviola.com/images/McLappConnectRJV021012.jpg
You can find other build examples in the fol. thread:
http://www.digitalhome.ca/forum/showthread.php?t=100137

Although the author probably intended to depict the M4 (9.5x9.0) size, he inadvertently ended up with a (10.5x9.0) instead, due to the extra 1-in connecting the Feedline to the Whiskers. In the (Whisker Length x Bowtie Separation) nomenclature, the Whisker Length is measured from the where the Feedline crosses the Whisker to the end of the Whisker. And I would recommend the M4 (10x9.5) size instead of M4 (9.5x9.0) if additional Gain is needed on the lower channels at the expense of the higher channels. All dimensions are described in the above posted 4nec2 Files.

And here is an example Grey-Hoverman explicity showing the Balun connection.....using Copper-Foil Tape on Cardboard:
http://macgyverisms.wonderhowto.com/...annels-0146459

Last edited by holl_ands; 08-14-2014 at 07:13 PM.
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