Loss of channels

[nomanselizabeth]

I installed a Winegard HD7084P last August on the recommendation of helpful individuals on this site. The antenna is mounted at a height of ~20ft, pointed at ~168 degrees in an open space although the majority of my lot in the direction the antenna points is wooded. There is no amplifier attached, nor a splitter as the antenna serves only one TV, which is about 25 ft total from the mast.

When I installed the antenna, I got very good reception on all the local channels, although sometimes NBC/Channel 11 had to be selected for a couple of minutes before the picture would show up. But that was the only hiccup.

About two months ago, I started having problems with Channel 8 becoming pixelated. I wasn't to concerned as that channel I knew to be in a different direction to most of the others, and I don't watch it that often. But now, I cannot get any picture with either channel 11 (NBC) or 46 (Fox). There is nothing, just static, and an error message saying weak signal. I have run the Program Channel- Air channels routine again, but no avail.

Here is my TVFool signal analysis
http://www.tvfool.com/?option=com_wr...05599dcdd8dfc5

Could anyone suggest what I might try to reaquire these channels?

[rabbit73]

You either have equipment failure or overload from very strong TV and FM signals. I don't know why teleview suggested a very large all channel antenna like that. You don't need VHF-Low, unless you want analog 4.
http://en.wikipedia.org/wiki/WUVM-LP

Previous thread:

Recommendations please
http://forum.tvfool.com/showthread.php?t=13414

It would have been easier for us to help you if you had posted this question on your previous thread.

.....although the majority of my lot in the direction the antenna points is wooded......But now, I cannot get any picture with either channel 11 (NBC) or 46 (Fox).

I wonder if some trees have now grown into the signal path?
http://www.hdtvprimer.com/antennas/siting.html
scroll down to Trees and UHF

WATC has a Noise Margin of 74.8 dB, even before adding the antenna gain.



Interpreting Noise Margin in the TV Fool Report

http://www.aa6g.org/DTV/Reception/tvfool_nm.html

WRDA FM 105.7 has a signal strength of -15.5 dBm. You should insert an FM trap, or two in series, between the antenna and the TV. See attachment 1.
http://www.mcmelectronics.com/produc...-FM-88-/33-341
https://www.antennasdirect.com/store...on_filter.html

It might even be necessary to insert an attenuator before the TV.
https://www.antennasdirect.com/store...ttenuator.html

[mikelessard]

Can you borrow a friend's little TV and test it?

[rabbit73]

Originally Posted by mikelessard

Can you borrow a friend's little TV and test it?

Good idea.

Originally Posted by nomanselizabeth

sometimes NBC/Channel 11 had to be selected for a couple of minutes before the picture would show up..... I started having problems with Channel 8 becoming pixelated.....But now, I cannot get any picture with either channel 11 (NBC) or 46 (Fox). There is nothing, just static, and an error message saying weak signal.

The noise level from electrical interference is higher on VHF-High, real channels 7-13, than on UHF. It is possible that it has increased lately. Is the coax shield grounded?

The coax shield should be grounded with a grounding block that is connected to the house electrical system ground with 10 gauge copper wire for electrical safety and to reject interference. 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.

[nomanselizabeth]

Thank you for your answers.

Regarding the trees in the immediate area - they are all older growth (25years+) so there has been no real change in the past year.

Grounding: both the coax and the antenna are grounded with copper as described, the coax to a grounding block, and the antenna directly to a copper rod in the ground.

I ran the channel setup (on Antenna- Air setting) again, and now have Channel 8 in nice and clear. So it is only Channels 11 and 46 (WXIA/NBC and WGCL/CBS) that are an issue. Forgive me please for being relatively antenna-unsavvy, but do you mean that the Channel 57/IND is so strong that it is blocking 11 & 46? Why would it not block the others? Would I possibly still see that 'Signal is too weak' error message, just because the TV doesn't have any other message to give?

[mikelessard]

This outfit - http://www.filtro.net/content/bandpass_filters.html - might be able to make a custom filter to weed out channel 57. It will need to be cut for real channel 41. If there's FM stations on Sweat Mountain you may need an FM trap too. I had issues with channel 11 in Cumming and it turned out that 97.1 The River was 5 miles away from me on the other side of the lake. A $2 Radio Shack FM trap did the trick for me.

Using Satellite grade cabling from the antenna to where it comes in the house may help too. It was $14 something for 50' at Frys.

[mikelessard]

Update - you will need a FM trap. There's a lot of stuff going on up there. Plus, the VHF-Lo componant of your antenna isn't helping. Try the FM trap first. It's cheap and easy.

http://en.wikipedia.org/wiki/Sweat_Mountain#Radio_2

[nomanselizabeth]

Thank you. I will go by Radio Shack tomorrow and pick one up. I will try this first, and then try contacting the Filter group regarding the custom filter.

Should I install the FM trap it before or after the ground box, or does it matter?

[mikelessard]

Before. I'd get it as close to the antenna as possible. If you're up for getting on the roof (and it's safe) I would buy the shortest pre-made RG6 cable I could get, attach one end to the antenna, the other to the "In" of the filter, then the existing cable to the filter "Out". Don't take any unreasonable risks though, it's not worth it. As long as it's inline between the antenna and the TV it will help.

I don't have your plot so I don't know how close to the mountain you are. I wouldn't be shocked if you needed 2 filters to get it all. In my situation with The River (97.1) my preamp has a built in FM trap, but it wasn't enough. I still had to add the 2nd trap. It is exactly 5.0 miles from our site.

[rabbit73]

Since you are not using a preamp, the FM filter, or two in series, can be inside. If you were using a preamp, it would go between the antenna and the input of the preamp.

If you order a custom filter to make real channel 41 (virtual channel 57.1) weaker, you must order a single channel bandstop filter for its real RF channel 41.

http://www.tinlee.com/MATV-Bandstops.php?active=3

[mikelessard]

Good deal. Thanks Rabbit! Let us know the results of the FM trap!

[nomanselizabeth]

Gentlemen, I went by Frys' to get the FM traps but, by virtue of the fact that there were none on the racks, ended up talking to a salesman. He said that both local stations 11 & 46 changed towers a couple of months ago; he works part time at one of the other broadcast stations in-town and says this was mentioned in meetings at the time. He remarked that a number of people have been in with the same question and since the tower change is the issue (in his opinion), neither an FM trap nor a channel blocker will help. His solution is to re-aim the antenna.

I am skeptical of the 'tower change' as the Signal Analysis database that this site draws from shows it to have been updated only a few days ago. I do not see any change or even a variance in the direction of WXIA/WGCL from most of the other local channels.

But before I go buying things I don't need, or messing with cabling, I thought I would ask you if this makes any kind of sense to you.

[mikelessard]

Haven't heard that. My antenna's pointed the same direction's it's been pointed since I put it up. What hasn't changed is all the FM stations on top of Sweat Mountain and your antenna with the VHF-Lo component. My FM trap was $2 and some change.

[nomanselizabeth]

Yeah, I know, I should have just gone ahead but I got intimidated by a determined sales guy who really had no intention of either pointing me toward the FM trap or finding out whether he actually had any in stock or not.

I caved, I admit........

[mikelessard]

You probably still have plenty of time to get to Radio Shack. Don't forget to get a short piece of RG6 cable to go from the trap to the TV. If they have any real short ones like 8" or 12" I'd get one of those.

If you haven't left yet get 2 traps and a barrel connector just in case. Try one first. You can always take the second one back if you don't end up needing it.

[mikelessard]

Never mind on the barrel connector - wrong gender. A second short cable piece.

[ADTech]

The sales guy was blowing smoke. There have been no technical changes at either station requiring a license amendment for almost a decade. A tower change would require one.

[nomanselizabeth]

Sorry for the delay in responding - work this week turned into a bigger hurry than usual!

I have added two FM traps in serial inside the house, just before the TV Antenna IN, seperated by a 1ft length of RG6. This has had the effect of returning the reception to the state it was when the antenna was installed i.e. I have Channel 46 back in lovely high def, Channel 11 is back, pixelated when first tuned in but clearing after a couple of minutes, and Channel 8 is viewable although tending to pixelate every so often.

In other words, the FM traps seem to have worked at restoring the set up to original condition, with a minimum of fuss and expense. Thank you so much for your advice, gentlemen! I really appreciate it!

[rabbit73]

Thank you for the report with good news.

There a few more things you can try to get 8 a little better. Try aiming your antenna a little more toward 8, like about 155 degrees magnetic.

Another thing to try is to add some attenuation; there might still be some overload problems from signals that are too strong. You can add a splitter or two (a 2-way splitter gives 3.5 dB attenuation) in the coax or you can buy a variable attenuator:
https://www.antennasdirect.com/store...ttenuator.html

Forum member tekeeladude had very good results using an attenuator:

Originally Posted by tekeeladude

I am using the Antennas Direct ATT-1 Variable Attenuator.

thread:
Too close to towers - Omaha
http://forum.tvfool.com/showthread.php?t=15574

[mikelessard]

That's great news Elizabeth! Had a pretty good feeling that would help. Is it possible that Sweat Mountain might just be blocking channel 8? Most of the towers are in the Briarcliff/Emory area. Channel 8 is a bit further east on Stone Mountain.

8's actually my best station, 57's the worst. I get a trace of once in a blue moon, never watchable.