antenna choice for 63105 St. Louis

[Bob]

I have a large, directional Radio Shack antenna installed in the attic of my 2 story house connected by coax to my Samsung LCD TV. No amplifier. There are several high rise buildings due west from me, some as close as 3 blocks. All the stations of interest are in a 60 deg arc centered at about 200 deg. I'm getting good digital reception from all stations EXCEPT Ch 9, and I don't know why. Ch 9-1,-2,-3,-4 all suffer from an interrupted signal from time to time. Somedays they all come in fine. Other days I can't get a signal at all. Other days the picture "stutters" and becomes very pixellated, making it frustrating to watch. It does seem the reception is worse on windy days, but my antenna is in the attic. Also, antennaweb shows Ch 9 to be in the same direction as Ch 2, and I get Ch 2 with no problems whatsoever. BTW, the analog Ch 9 has always given me a poor picture. I was thinking a new multi-directional antenna would solve my problem, but after browsing the forum and other info I'm beginning to doubt it. Perhaps I need to add a second antenna for complete coverage...but I know nothing about the practicality of combining the signals. Please advise. Thanks!

[tigerbangs]

You are experiencing a multipath condition that is exacerbated by your antenna's attic location: relocating the antenna outdoors with proper aiming will solve your problem.

[Bob]

Thanks for your suggestion.

I have seen on the wepsite that there is a lot of resistance to attic installations. Why? The attic antenna is away from the many sources of interference and blockage typical for the living area, just not outside blowing in the breeze. Do the roofing nails create a source of interference? Outside gutters?

The house is located at the top of a small hill and the antenna is about 25 feet above the ground. If I move the antenna from that attic to outside, it will only move about 10 feet higher up but be a lot of trouble with a two story house with steeply pitched roof.

Also, why would Ch 9 be more susceptible to multi-path than Ch 2, since they are on the same azmuth from my house, just different distances?

Regardless, after reading your post I finally thought to use the signal strength meter on my TV. For whatever reason, Ch 9 is only 2 bars, while every other station is 4+ bars. Maybe PBS is trying to save electricity!

Again, thanks for your reply.

[tigerbangs]

Roofs are not transparent to TV signals: they vary in their resistance to TV signals depending on their construction, age and insulation. There isn't any way to predict how your roof will block TV signals without actually trying it. My rule of thumb is to assume that you essentially cut the available TV signal at the antenna in half when you mount an antenna in an attic. Roofs with foil-backed insulation, HVAC ducting, stucco walls, concrete tiles and steel roofs block almost all available TV signal to an attic-mounted antenna. From this distance, I can only have confidence in an outdoor antenna when predicting performance in any given location.

[Bob]

I can certainly appreciate your reluctance about antennas in attics, now that you point out the potential problems!

As it turns out, these are features of newer construction. In my attic, all the insulation is between the floor rafters, no foil anything, no metal ductwork or electrical wiring above the floor rafters, and the roof is asphalt shingle on wood sheathing. The only metal, per se, in the line of sight of the antenna is what is in the roofing nails.

I'm going to try tweaking the direction of the antenna while referring to the signal strength meter, and see if a few degrees can't buy me a few more bars without degrading much the strength of the other signals. If that doesn't work, I might add an amplifier upstream of the splitter. Do you think that is a viable option?

Thanks,

Bob

[tigerbangs]

An amplifier will only help you overcome line losses AFTER you calculate in the noise factor of the amplifier. Contrary to what you may think, an amplifier does not make a weak have better signal-to-noise ratio. It doesn't make a signal out of no signal...LOL If the signal is weak at the antenna, then the preamplifier can't actually help you. If your low signal condition is a result of line losses after the antenna, the a preamplifier can help you. A preamp isn't able to fix a multipath issue, however...

[tvreception]

I have installed quite a few attic antennas, and I have found that separate UHF and VHF antennas seem to work better. One of the reasons that they work better is that signal strengths vary considerably in different areas of the attic. Having separate antennas allows you to move the antennas to where they work best. I have found that moving the attic antenna by a couple of feet (all directions) can make a huge change. Installing an attic antenna takes time and patience to get it all to work right, and many times it does!


Steve
http://tvreception.net

[Bob]

Thanks for the benefit of your experience. I will add that to my list of possible actions to take to battle any reception problems. The LAST thing I will do is move the antenna to the roof proper. Just too much of a headache...and I'd have to pay someone to do it.

However, in my particular situation, the bad station is just one of several VHF stations. It just happens to be a little farther than the others, but still within 15 miles of my house.

I am going to wait until everything is digital and ALL the stations finally go to full strength before I do anything. I don't see the point in this less than full strength business and that some stations seem to be waiting until the very last minute to broadcast a digital signal, requiring a "rescan Monday".