Poor reception on high VHF

[Rmlev]

I have a Radio Shack "swept wing" type VHF/UHF/FM roof antenna, about 20 feet from ground. In recent months, high VHF stations (7, 9, 11, 13) have become very erratic, with 7 and 9 sometimes dropping out entirely. As far as I am able, I have aimed the antenna at the recommended azimuth (43-44 degrees). I've tried rotating the antenna on either side of this - makes no difference. Day or night doesn't seem related.

Here is the link for the signal at my location:

http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3dd243b930ff8b56

I'm pretty naive - do antennas "wear out?" It's about 14 years old. Any other explanations/suggestions much appreciated.

Thanks very much.

[Jake V]

First, I'd inspect the antenna. Manually check each connection. One could be loose. After 14 years the antenna could be fine but the coax could be failing.

If there is a splitter, it could be failing.

If the antenna is physically fine I'd run a single length of new coax direct from the antenna to one television to see if it fixes the problem.

If you need to replace it I'd go with something like an Antennacraft HBU11 or an RCA ANT751.

[Rmlev]

Thanks for the suggestion, Jake, I'll try to do that. But I'm not clear why a bad connection or degraded coax would cause only those particular channels to drop out - the other VHF and the UHF channels are fine.

[Stereocraig]

Thanks for the suggestion, Jake, I'll try to do that. But I'm not clear why a bad connection or degraded coax would cause only those particular channels to drop out - the other VHF and the UHF channels are fine.

It sounds to be a matter of only the strongest channels overcoming whatever problem is sapping your signal and more channels will join the list, as the problem worsens.

Antennas really don't wear out, unless the rivets are extremely rusty, or loose.Replacing any coax, baluns, or splitters, is good advice.

You may want to use penetrating oil and a wire brush on the wing nut terminals.
If they are rusty, be careful not to snap them off.

[No static at all]

Any amplifier or splitters?

Also you have a few FM stations in town that may be having an effect as well. Run an FM Fool report & see if any stations are less than 3-5 miles away.

[tomfoolery]

And don't forget the balun. Don't assume it's still good after all those years in the weather. A little water can get into it or the coax connections, too, plus not all baluns are built with the same quality to start with

[Stereocraig]

And don't forget the balun. Don't assume it's still good after all those years in the weather. A little water can get into it or the coax connections, too, plus not all baluns are built with the same quality to start with

FWIW, I prefer solid wire leads on baluns, as opposed to spade terminals.

[Tower Guy]

I vote for a broken wire on one side of the balun.

[Rmlev]

I'll go up top tomorrow and start checking - hopefully the simplest explanation will be the truth. Thanks for all the help so far. :)

[Rmlev]

I replaced the balun and cleaned the visible corrosion from the coax central conductor, and now have strong signal from all channels. I'm still curious why the problem was only with those VHF channels, but all is good at this point.
Much appreciate the help.

[ADTech]

Because the corrosion acted like a capacitor which was the wrong value to pass VHF signals.