VHF high signal "disappeared" from GH10n3 - Page 2 - Canadian TV, Computing and Home Theatre Forums

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post #16 of 24 (permalink) Old 2019-07-07, 03:10 PM
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Quote:
Originally Posted by lenlab View Post
I had 2 CM7777 preamps sitting on a shelf collecting dust so I thought I would give them a try at resolving my issues with 7.1 and 11.1. I tried both of them and they did not resolve the issue. I know the FM filter works because if I turn it off I lose 13.1. What I don't know is if the FM filter in the preamp is actually effective for the 11.1 and 7.1 signals.

If the cm7777 has a good FM signal trap then my issue is not FM signal related but something else is going on impacting signal quality.
The FM filters in preamps are not as effective as a separate FM filter/trap.

The best device for a test would be a HLSJ inserted between the VHF antenna and the preamp; use the High and Line ports. It has a low insertion loss and will block everything below CH 7, including FM.



I'm still guessing because I haven't seen your exact address FM signal report. You can do one here:
http://www.fmfool.com/index.php?opti...pper&Itemid=29

If you can not measure it, you can not improve it.
Lord Kelvin, 1883

Last edited by rabbit73; 2019-07-07 at 04:41 PM.
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post #17 of 24 (permalink) Old 2019-07-08, 09:11 AM
 
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Location: Randolph NJ 30 miles west of ESB/1WTC
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rabbit73,

My VHF antenna feeds a Blonder Tongue ZHLSJ and then that VHF output feeds a CM distro Amp. So the ZHLSJ is either not working for 7.1 and 11.1 or the problem is not FM noise.

I did not know about this FMFOOL site. I will message you with my exact address so you can see the results. It would appear there is a lot of potential FM interference. However the CM7777 and the ZHLSJ don't seem to point to that as being my issue.

Last edited by lenlab; 2019-07-08 at 09:47 AM.
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post #18 of 24 (permalink) Old 2019-07-08, 09:46 AM
 
Join Date: Apr 2017
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One thing I learned and found surprising when I hooked up the dust covered CM7777 preamp to test the fm trap. I did one experiment where I fed my VHF antenna into the CM7777 and set the switch to combined input and fm trap on and not only did I get VHF 13.1 but all of my UHF stations with strong signals! So even if you have a VHF only antenna if you are combining it with a UHF antenna it is probably a good idea to split out the UHF signal it might be grabbing before you combine them and vice versa with the UHF antenna.
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post #19 of 24 (permalink) Old 2019-07-08, 07:35 PM
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Quote:
Originally Posted by lenlab View Post
My VHF antenna feeds a Blonder Tongue ZHLSJ and then that VHF output feeds a CM distro Amp. So the ZHLSJ is either not working for 7.1 and 11.1 or the problem is not FM noise.

I did not know about this FMFOOL site. I will message you with my exact address so you can see the results. It would appear there is a lot of potential FM interference. However the CM7777 and the ZHLSJ don't seem to point to that as being my issue.
Thank you for the additional information by PM. It allowed me to make a more thorough analysis.

I answered your PM; hope you got it.

Thank you for making the FM tests. I did an FM Fool report for your location that shows the risk of FM interference is small. The strongest FM transmitter is 2.4 mi away but is only running 1 kW with a signal power of -32.1 dBm on 105.5 MHz. Its second harmonic would interfere with CH 13, but you get that OK.

I can post your TVFool TV and FM reports, and a rabbitears.info report image, but only with your permission.

I also have some satellite images that show a lot of trees in the signal paths. The NY signals not only have to go over rough 2Edge terrain, but through the trees to get to your antenna. I think that 13.1 does better, even though it is listed as weaker, because it is coming in on a different azimuth (111 deg) than 7.1 and 11.1 (105 deg).

I can also post the sat images with your permission.

I see solar panels on your roof. Are they solar electric or solar thermal? If they are solar electric, I would suspect inverter interference.

In the Google street view (2013), I see an antenna and I also see that the ground rises as you go up the hill to the SE.

If you can not measure it, you can not improve it.
Lord Kelvin, 1883

Last edited by rabbit73; 2019-07-08 at 10:32 PM.
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post #20 of 24 (permalink) Old 2019-07-09, 09:21 AM
 
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Rabbit73,

Yes I got your PMS and the info so thanks a bunch. I will PM you back.

There was a suggestion that I continue this discussion on my specific reception issues on the forum thread where I discuss possibly modifying a UHF antenna to make it VHF.

However that being said. This morning I found that I was getting 7.1 with 100% signal strength and 30% quality. Good enough to be locked in w/o breakups. It might be due to troposhpere issues as we had rainy weather. Although the sun is shining this AM.

Now here is the really strange part and I swear this is the truth. I disconnected the feed to my distro amp so I could change and experiment with the connections to the ZHLSJ and UVSJ combiners etc and even though there were NO physical connections to the distro amp 7.1 was still on the TV coming in fine. How could that be? I can't explain it. MAybe the experts on this forum could. The end of the VHF coax had to be about a foot from the distro amp so maybe it was just close enough for the signal to be picked up.

All the changes I tried did not improve the signal on 7.1.
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post #21 of 24 (permalink) Old 2019-07-09, 01:42 PM
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That must be some extreme tropo. Troppo or not, the signal must be leaking in from somewhere. Bad cable or connection? That could be the cause of the issues. A preamp plus distro amp can sometimes cause issues. What happens of the distro amp is taken out?
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post #22 of 24 (permalink) Old 2019-07-09, 03:36 PM
 
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ExDilbert,

I guess I caused some confusion with some of my posts. While I did dust off the 2 CM 7777 preamps I had. I only hooked them up temporarily to experiment with their FM filters. They are back on the shelf collecting dust.

My current setup is from the antenna to a powered CM distro amp which then distributes the feed to 4 devices. I do use a combiner to bring my UHF and VHF antennas together before the distro amp.

I have tried to feed directly to the TV and or DVR+ w/o a distro amp and still no 7.1 or 11.1.
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post #23 of 24 (permalink) Old 2019-07-09, 03:39 PM
 
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Still can't explain how the TV can get 7.1 when there is NO antenna cable connected to the distro amp! It was a foot away!

I should have tuned to 13.1 to see if this was a constant.

I may repeat the experiment again just to prove it was no fluke unless one of the engineers on this forum comes up with a valid explanation that proves I'm not crazy!
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post #24 of 24 (permalink) Old 2019-07-09, 03:42 PM
 
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Matt Atchley,

I want to apologize for taking over your thread! Any further discussions about my circumstances with VHF reception will be continued on my thread about UHF antenna conversion to VHF.

Len
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