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Best Antenna for VHF 12 (KNTV) with bad LOS

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Old 06-25-2010, 05:46 PM   #1
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Default Best Antenna for VHF 12 (KNTV) with bad LOS

Hi.

I tried to past my tvfool url, but the app won't let me. I'm at 1207 Scott St, SF, 94115

Using an indoor UHF/VHF antenna I get every station just fine (most broadcasting from 2 miles and 205 degrees). But I don't get NBC KNTV, which is VHF 12, broadcasting from 179 degrees, and is only 6.5 miles away. Since I don't get any other stations broadcasting from that tower, and from what I've read, it appears to be a line of sight issue.

What would be the best (cost-effective) solution to add this channel? Would ANY antenna really be able to pick this up? And do I have to get a whole second antenna and connector?

Jeez, what it takes to get stupid NBC, I am starting to wonder if it is worth it!

Thanks in advance

JSM
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Old 06-25-2010, 07:53 PM   #2
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Quote:
Originally Posted by jsmneedshelp View Post
Hi.

I tried to past my tvfool url, but the app won't let me.
http://www.tvfool.com/?option=com_wr...9fbec9150bc60e

You are LOS to NBC.
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Old 06-25-2010, 08:13 PM   #3
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Quote:
Originally Posted by jsmneedshelp View Post
Hi.

I tried to past my tvfool url, but the app won't let me. I'm at 1207 Scott St, SF, 94115

Using an indoor UHF/VHF antenna I get every station just fine (most broadcasting from 2 miles and 205 degrees). But I don't get NBC KNTV, which is VHF 12, broadcasting from 179 degrees, and is only 6.5 miles away. Since I don't get any other stations broadcasting from that tower, and from what I've read, it appears to be a line of sight issue.

What would be the best (cost-effective) solution to add this channel? Would ANY antenna really be able to pick this up? And do I have to get a whole second antenna and connector?

Jeez, what it takes to get stupid NBC, I am starting to wonder if it is worth it!

Thanks in advance

JSM

Quote:
You are LOS to NBC.
Depending on his AGL , he's borderline 2-edge from Bruno (play with his heigh in the MAPS tool) with LOS to several very hot FM stations coming from Sutro. At least two of them have 2nd harmonics that fall into channel 12 and are are each forecast to be at -15 dBm at his address. Those are each 25 dB hotter than the forecast for channel 12.


jsmneedshelp.
You NEED an FM filter (maybe two in series)...and no amplifier if you're using one. An HLSJ would also work.

Last edited by projectsho89; 06-25-2010 at 08:30 PM.
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Old 06-25-2010, 08:58 PM   #4
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LOS to several very hot FM stations coming from Sutro. At least two of them have 2nd harmonics that fall into channel 12 and are are each forecast to be at -15 dBm at his address.
I agree. Nice catch.
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Old 06-26-2010, 12:08 PM   #5
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hey guys, thanks for your replies on this.

does the tvfool app REALLY understand LOS and topography? Twin Peaks at 945 ft. is sort of in between myself and Mt. San Bruno at 1300 ft. It is probably about 10 degrees off of the direct LOS, but I can't seem to see the peak even on the clearest days due to the hill.

Since the tv tuner reports a barely perceptible signal, I was thinking it was an LOS issue rather than an interference issue. Given this info, do you still think it's just an fm interference issue?

Sorry for my incomplete knowledge on this and thanks for your help.
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Old 06-26-2010, 06:10 PM   #6
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TVfool understands your terrain and LOS very well as do both TG and I.

It is interference problem, not a signal power issue.

Your tuner isn't displaying the power of your signal, it's reporting a composite value that is heavily weighted with the error rate of the decoding of the signal. A high error rate will show the same as a very low power signal.

It is always possible that you have multi-path problems. However, with those FM signals blasting directly at you and the known effects on VHF that they cause, it would make no sense to ignore the obvious issue first.

Last edited by projectsho89; 06-26-2010 at 06:15 PM.
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Old 06-27-2010, 09:36 AM   #7
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Well, I will pursue the interference issue then.

The other factor I forgot to mention is that I have no signal strength with the other stations broadcasting from the same tower as KNTV (28 and 65). A post by a KNTV technician on another forum had indicated that no signal strength from these other stations indicated blockage.

I'll try the interference angle based on your advice.

Thanks,
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Old 07-01-2010, 01:04 PM   #8
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Hey guys.

Well, I've been to Radio Shack, and a couple of specialty TV stores. I'm striking out on the FM filter. Part of this is due to my ignorance regarding exactly what I am looking for.


Do I need a tunable trap?

Looking around I've found something like this:

a: Winegard FT7600 Two Stage Variable FM Trap
b: Radio Shack 75-Ohm Coax FM Trap 15-577C
c: Radio Shack 75 Ohm TV/VCR/FM Interference Filter 15-579A

What's the best choice? What will work? Suggestions?

Thanks!
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Old 07-01-2010, 04:45 PM   #9
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The WG trap would take special equipment to tune properly.

Th RS 15-577x would work. The 15-579 is a CB filter and will not work..

Additional choices are FMFLT from Antennas Direct or the HLSJ from either Holland Electronics or Pico Macom (available from Solidsignal.com). If you go with the HLSJ, install a 75 ohm terminator resistor on the "L" port.

Whatever you get, get two of them. You might need to double them up in series. The devices are cheap, you'll pay more in shipping than for two or three of them.

Last edited by projectsho89; 07-01-2010 at 07:13 PM.
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Old 07-01-2010, 05:30 PM   #10
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Quote:
Originally Posted by jsmneedshelp View Post
Do I need a tunable trap?

What's the best choice? What will work? Suggestions?
I wouldn't recommend a tunable trap. They are intended for one strong signal at a time. You have multiple FM stations to null out.

I vote for the HLSJ. (or two of them)
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Old 07-02-2010, 12:14 PM   #11
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Having trouble finding the Holland HLSJ. How about a Pico Macom HLSJ VHF Band High-Low Antenna Separator-Combiner (HLSJ)? I found it on Solid Signal () Part number

And can't find the fmflt at antennasdirect (they have no search function on their site!) but I did find a FM Band Rejection Filter???

I'd post the links, but highdefforum will not let me post anything with a url address ;(


Thanks!
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Old 07-02-2010, 12:43 PM   #12
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The Pico Macom is just as good if not better than the Holland. 2 HLSJ's should knock down the entire FM band around 40 db, but I would try just 1 first & see if it does the trick. (But order 2 just in case)
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Old 07-02-2010, 01:58 PM   #13
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The FMFLT is the FM band rejection filter. The item number pops up when you look in your cart.

Either the Holland or Pico HLSJ is fine. Do NOT forget the 75 ohm terminators.
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Old 07-13-2010, 12:39 PM   #14
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Hey guys,

If you are still monitoring this thread, I lined up 2 of the Pico's with the terminators. The good news is that the station is barely viewable now. The bad news is that the signal strength still says low, and the image breaks up even when I am optimizing the antenna position.

I'm trialing a radio shack indoor antenna: http://www.radioshack.com/product/in...ductId=3912573

Do you think that I need a different (outdoor) antenna in addition to the HLSJ's?

Thanks,

Jeff
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Old 08-10-2010, 08:49 AM   #15
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Hi. If any of you experts are still seeing this thread, I have NOT been able to get a decent signal on the station in question even with the filters and trying out a few antennas. I have not yet invested in an expensive big antenna yet, as I'm somewhat skeptical that it will provide a solution given that TVFool and y'all state that signal strength should not be an issue.

Is there some frequency specific antenna I need? Or what would your recommendations be?

I have a question about the TV Fool output as well. Is it truly address specific? Or is it zip code specific? Here in San Francisco, one part of a zipcode may have radically different LOS issues than another part of a zip code due to the large hills. I am wondering if that could possibly account for the signal strength discrepancy???

Thanks
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