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Old 10-Jan-2016, 3:30 AM   #1
ctm
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Join Date: Jan 2016
Posts: 2
Help with weak stations

Hi and Happy New Year!

Where I live, there's two stations that are extremely strong, and the rest are extremely weak.
The "least weak" stations are in roughly the same direction as the strong stations (towards the south-south-east), and towards the west & north, there are weaker, more distant stations.

Here's the TVFool report:
http://www.tvfool.com/?option=com_wr...b97dfc51c02d8d

The receivers are a SiliconDust HomeRun Extend (for time shifting programming), and a samsung tv.

Ive been experimenting with a DB-8e antenna with a Wineguard preamp.
Pointing it towards the weaker stations about 50 miles away (at 136 degrees), I get a signal from the weaker stations, but not enough to get a picture.
The two strong stations come in really, really well.
While at 136 degrees, I can also receive two stations from over 75 miles away, with a good signal.
These two stations are in a different direction (about 190 degrees), and dont show up in the report.

When pointing west or north, there's some signal but no picture from any of the stations.

The antenna site (a re-purposed power pole) now has trees grown up around it, and Im sure that's not helping, either.

Is it possible to receive the weaker stations? And, if so, what would it take to receive them?

Any thoughts are appreciated!
Thanks,
-Cliff
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Old 10-Jan-2016, 5:30 AM   #2
StephanieS
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Join Date: Aug 2012
Posts: 442
Greetings CTM,

You are correct, the very strong and very weak signal situation is a difficult one. This type of situation is one of experimentation. Luckily, all your signals with the exceptions of WCYB and WBRA are all UHF.

First the preamp. With 73 db signals nearby and being 20 degrees off, I wouldn't run one. Remove it and see how your antenna does strictly using its own gain.

There are methods to null, or modify an antennas ability to receive so that the very strong signals are attenuated or lessened in a particular direction. Here is some information on this technique. It requires two antennas and spacing them:

http://www.hdtvprimer.com/ANTENNAS/ganging.html#TAT

There are some other options such as filters that block or greatly reduce signals on one specific channel. Those aren't cheap. Rabbit73 can provide more information on this.

Further complicating your situation is that your weak signals are very weak. Generally around 7db signal strength is when atmospheric conditions can start to affect the signal so that it comes and goes. Could you run a TV fool map at 50', 75' and 100'? If you can get the very weak UHF signals to around 10db signal strength, your chances will improve greatly.

Your situation isn't going to be one of "plop a 40 dollar antenna in the air." It's going to require some testing, engineering and creativity. It's doable, but may be a bit more intensive than you are looking for. And yes, trees are a signal killer. It's strongly advised you get above them or trim them so the antenna has a clear view of the horizon in the case of the very weak signals.

Cheers.
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Old 10-Jan-2016, 11:22 AM   #3
Tower Guy
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Location: Delmar, NY
Posts: 1,192
Reception of the weaker group of stations will require nulling of the two close-in stations and an overload resistant preamp. The DB-8e is the best antenna for you. The side by side panels have a natural null at about 21 degrees off axis on channels 31 and 32. Your strongest stations are 24 degrees off axis. The trick will be to aim the antenna so that 31 & 32 are as weak as possible. You'll have a 3 degree aiming error on your desired stations, but that won't matter.
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Old 10-Jan-2016, 3:41 PM   #4
rabbit73
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Location: S.E. VA
Posts: 2,570
Good idea by Tower Guy; that will help a lot.

Credit also to StephanieS for suggesting the Two-Antenna Trick, Outdoor which is the general method used to produce the null.
Attached Images
File Type: jpg DB8e pattern2.jpg (208.7 KB, 338 views)
__________________
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Last edited by rabbit73; 10-Jan-2016 at 3:58 PM.
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Old 10-Jan-2016, 8:58 PM   #5
ctm
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Join Date: Jan 2016
Posts: 2
Wow, thanks for the advice!

Ganging two DB-8e antennas may be the way to go, or at least worth testing.

StephanieS, here are the reports
at 50'
http://www.tvfool.com/?option=com_wr...5134f391ff6ac3
at 75'
http://www.tvfool.com/?option=com_wr...513463f81f46f8
and at 100'
http://www.tvfool.com/?option=com_wr...513442cc7e53b9


The two strong stations are at 111-112 degrees, and the weaker one's are at 136 degrees.
Is that utilizing the null in the lobes 20-22 degrees off center?
When the antenna first went up, I had mistakenly pointed it at 150 degrees, but that was before the preamp, and it did show a significant drop in signal for the two strong stations, but no useful signal for the other stations.
I'll be rotating the antenna and taking more measurements - after the winter weather clears a bit.

Below are some of the measurements I made while testing the DB-8e antenna.
Im going by the signal strength indicator in the HDHomeRun's software, hdhomerun_config_gui.app.
The signal percentages have been consistent over the past few days.

At 136 degrees, I recorded these signal strengths.
M1 = no preamp; M2 = with preamp; * = picture

Channel M1 M2
17 - 50%
19 - 49%
22 - 34%
23 - 37%
27 54% 66%*
31 63%* 90%*
32 75%* 100%*
33 - 43%
34 39% 65%*
36 - 29%
44 29% 51%*
50 - 26%
51 - 36%

(apologies, looks like the forum's html doesnt like multiple spaces, Ive attached the chart as a jpg)

Looks like the 'digital cliff' needs more than a 50% signal in the hdhomerun to get a picture.
The preamp in the circuit gets a picture for three more stations, unfortunately, not the one's Im going for - but still a good surprise.
It looks promising that (maybe) ganging two DB-8e antennas would improve the signal over 50% on several channels enough to get a picture.

I first started my testing with a 91x antenna, which only got a picture on the two strong stations. The DB-8e seems to work much better in my situation.

I know the biggest issue Ive got is the trees. Currently, the antenna is facing right into them. Im estimating I'd need a tower 60' or better to clear them.

Cutting trees may be an option, but I'd estimate it would be taking down around 20-30 trees for a narrow 'window'.
Another option is to move the antenna site about 300'-400' from the current location into a field at the top of a hill behind the house, where there are minimal trees in the way.
None of these options are out of the range of possibilities, but it does get into "effort vs. diminishing returns".
hmmm... maybe it's time to play the powerball lottery! ;-)

Sidenote...
I have a Panamax surge surpressor for the equipment, and it has surge protection in/out connections for coax.
When it was in-line, the signal drops by at least 10-15%!
It's out of the circuit in the above measurements - and will remain out!

Again, THANKS for the help!
Attached Images
File Type: jpg antenna.jpg (13.7 KB, 295 views)

Last edited by ctm; 10-Jan-2016 at 9:04 PM.
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Old 11-Jan-2016, 1:02 AM   #6
StephanieS
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Join Date: Aug 2012
Posts: 442
Thanks for the added height plots.

Indeed with elevation signal access does begin to improve at @ 75' At 100', it's even better. The upshot as you've already noted is how much effort are you willing to invest in this.

The hill behind your home sounds interesting however pushing 400+ ft. of cable will require considerations to signal loss. I might before I committed heavily, at that hill with minimal trees put your antenna of choice a few feet above ground and aim it at the weaker signals. See what the reception is with a shorter run of coax and a generator powering a TV.

Can you also adjust your plot slightly to reflect the hill location at 25, 50, 75 and 100'?

Cheers.

Last edited by StephanieS; 11-Jan-2016 at 1:05 AM.
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Old 11-Jan-2016, 2:04 AM   #7
rabbit73
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Location: S.E. VA
Posts: 2,570
Quote:
Ganging two DB-8e antennas may be the way to go, or at least worth testing.
No, you don't want 2 DB8e antennas. Your single DB8e contains 2 4-bay antennas that give you the null to make the strong signals weaker. Two DB8e antennas would make the beamwidth too narrow.



Quote:
Ive been experimenting with a DB-8e antenna with a Wineguard preamp.
Which preamp? You need a preamp that is highly resistant to overload.
Attached Images
File Type: jpg DB8e pattern2.jpg (184.4 KB, 772 views)
__________________
If you can not measure it, you can not improve it.
Lord Kelvin, 1883
http://www.megalithia.com/elect/aeri...ttpoorman.html

Last edited by rabbit73; 11-Jan-2016 at 3:19 AM.
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