Help with hill-shielded antenna

[RichardSwe]

I live in the shadow of hills that block line of sight to San Francisco broadcast towers. From what I've seen it looks very unlikely I can pickup a signal. But I'm hoping anyway.

Here is my signal analysis link:
http://www.tvfool.com/?option=com_wr...f1f0b1f83ca6b4

I am interested primarily in picking up ABC, NBC, CBS and PBS stations. Broadcast 7, 12, 29 and 30. There are a couple alternatives for PBS. I just chose the one I'm most familiar with and off the same broadcast tower as 7 and 29.

My first choice would be to find a contractor with experience near where I live in the hill shadows. I have been trying but no luck so far in finding someone.

My second choice is to try it myself -- trial and error by an amateur. I probably could do this, but I'm less sure. I am quite handy -- e.g. I've pulled cable throughout house from a central hub setup I installed. Running antenna coax to that hub will be easy.

Thanks for any advice and ideas.

[rabbit73]

Welcome, Richard:

Yeah, those hills are a problem. If you are willing to experiment with a temporary test setup, I suggest a Winegard HD7698P aimed at 255 degrees magnetic, and an Antennas Direct Juice preamp.
https://forum.tvfool.com/showpost.ph...93&postcount=3



This is what the KNTV terrain profile looks like. Notice that the ERP is only 28 kW out of 103 in your direction:



And this is for KQED:



The signals from VHF real channels 7 and 12 have a better chance of diffracting over the peaks of the hills than the UHF channels. It might help if you tilted the front of the antenna up a little. The 7698 doesn't have a tilt adjustment, like the UHF only 91XG, so it would be a custom modification.

I tried different heights using an estimate of your location. It helped a little, but not a lot. Your 2Edge signals aren't likely to be 100% reliable, but I think your chances are good if you don't have trees or buildings in the path between your antenna and the hill peaks.
25 ft
http://www.tvfool.com/?option=com_wr...f1f01671c787ce
50 ft
http://www.tvfool.com/?option=com_wr...f1f0478fef5d1f
100 ft
http://www.tvfool.com/?option=com_wr...f1f0a8cfc42863

It might be possible to get a little more gain from two separate antennas, one for UHF like the 91XG or DB8e, and an Antenna Craft Y10-7-13 for VHF. But try the 7698 first.

You don't seem to have any strong FM signals that might interfere with 7 an 12; the Juice doesn't have an FM trap. The Channel Master 7777 or 7778 do. See attachment 3.

The coax should be grounded with a grounding block that is connected to the house electrical system ground with 10 gauge copper wire for electrical safety. For further compliance with the electrical code (NEC), the mast should also be grounded in a similar manner to drain any buildup of static charge, but the system will not survive a direct strike.

[RichardSwe]

Rabbit73 --

Thanks. You've given me some hope and a lot to consider. I'll follow your suggestions, first trying for signals with the Winegard HD7698P. If that shows success with VHF channels 7 & 12, I will dive in more.

A question on the practicalities of aiming the antenna:
As a first pass trial of reception, I would plan to aim the antenna from my roof (single story house). How specific is my goal in the degree aiming... +/- 5-10 degrees?

From my roof top, I may have a "line of sight" to the 255 degree hill top, but trees may interfere. A taller mast could probably overcome the trees but that would come with a more committed approach if I can get some positive results off the roof top.

I can ground the coax easily in the hub for my house AV / ethernet wiring. Currently my cable coax is grounded coming in and all TV coax shares that ground. The wiring hub has a ground also that I can use for the antenna coax. If I end up with a mast, I can ground that also.

If this sparks some more ideas, thanks ---

Richard

[rabbit73]

A question on the practicalities of aiming the antenna:
As a first pass trial of reception, I would plan to aim the antenna from my roof (single story house). How specific is my goal in the degree aiming... +/- 5-10 degrees?

Interesting question. There is the straight forward practical part, that concerns signal strength. How critical the aim depends upon the horizontal beamwidth of the antenna that is given in terms of the halfpower (3 dB down, or 0.707 voltage) points (HPBW). Generally, the higher the gain, the narrower the beamwidth, which is an inherent trade-off, because energy cannot be created or destroyed, only converted. Or, as ADTech likes to say TINSTAAFL

http://www.antenna-theory.com/basics/radPatDefs.php
http://www.cisco.com/c/en/us/support...vs-direct.html

Looking at the beamwidth charts for the 7698, I see different answers, but think the chart at solid signal is wrong:
http://www.solidsignal.com/pview.asp?p=hd7698p
Click on specifications, and scroll down to the chart below Step 3

And also wrong here:
http://www.winegarddirect.com/viewit...HD7698P)&post=

The correct Winegard chart is here:
http://www.winegard.com/kbase/uploads/HD7698P.pdf

The more esoteric part concerns signal quality. I have found that if I make the initial aim based on signal strength, and then monitor signal quality based on SNR and errors, I am able to optimize aim. The greatest signal strength and the best signal quality aren't always at the same azimuth. Go for signal quality. My Sony TV has a diagnostics screen that gives signal strength, SNR, and errors.

You can use the green signal lines from the tvfool interactive map feature to help you aim. You can move the teardrop cursor to the exact antenna location. Then pick a landmark.

Please tell us how it works out. We need the feedback to know if our advice was accurate.

[RichardSwe]

OK - thanks for your patience. I'm clearly a neophyte here.

I went on my roof to scout out broadcast azimuths. My first estimate of channels to try for is likely wrong.

Here are two views of broadcasts of ABC, NBC, CBS channels. In each photo the degree azimuth is about the center of the photo and is the magnetic bearing.


View towards 244 degrees (channels 7, 12, 29, etc.) - appears to be completely blocked by large trees. I am assuming this won't work.


View towards 24 degrees (channels 10, 25, 35) -- The hill involved is visible in the center.

So, it appears to me that I may have more success with the 24 degree azimuth.

Any opinion about the trees causing problems for the 244 and 24 degree azimuths? Unless success seems highly unlikely, I'll go ahead with the Winegard HD7698P and try to catch some channels.

[rabbit73]

OK - thanks for your patience. I'm clearly a neophyte here.

I'm still learning, too.

Thanks for the photos.

Oh, my. First it was the hills, and now it's the trees.
http://www.hdtvprimer.com/antennas/siting.html
scroll down to Trees and UHF

http://www.wrightsaerials.co.uk/refe...-reception.pdf

Your first photo reminds me of this:



In the photo above Kevin is using a WG 7697P. If you want to read more about his tree problem:

http://www.avsforum.com/forum/25-hdt...l#post17280909
http://www.avsforum.com/forum/25-hdt...l#post17283385
http://www.avsforum.com/forum/25-hdt...l#post17297708

ADTech's post about trees:
http://forum.tvfool.com/showpost.php...90&postcount=3

View towards 24 degrees (channels 10, 25, 35) -- The hill involved is visible in the center.

Umm, I don't see the hill, but the trees don't look as bad.
However, the signals from 24 degrees are a little weaker.

Is there any location on your lot that doesn't have trees in the path from 244?

How difficult would it be to go higher?

Here is a list of networks in your zip code from rabbitears.info. Click on a call sign and it will expand to show subchannels.
http://www.rabbitears.info/search.ph...pe=dBm&height=

The tvfool report is only a computer simulation; sometimes it's a little off (either way) especially with 2Edge signals. There is a little less hope now, but you might want to take a gamble with a test to satisfy your own curiosity, before getting any deeper into this.

[RichardSwe]

Originally Posted by rabbit73

First it was the hills, and now it's the trees.

Well, the good new is that there are no sunspots to deal with so far.




Thanks for the wealth of information. I'm enjoying the reading, even if feeling discouraged. Don't know yet where I'll land. I'd still like to at least try...

Will report back hopefully.

Richard