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Does water on roof affect attic antenna reception?

1060 Views 2 Replies 3 Participants Last post by Dibenzylacetone, May 13, 2006

Teeh

Discussion Starter · May 13, 2006

My rooftop UHF yagi antenna and a few others I am aware of provide better TV signal strength across all freqs in foggy, cloudy or rainy weather. This behavior is often claimed to result from the effect of tunneling due to temperature inversion (warmer up, cooler down) and concentration of wave energy by moist air.

Contrarily, I am told of an attic antenna installation where signals are weaker and more dropouts occur during rainy weather.

So I'm asking whether anyone else has experienced this and confirmed the exact cause? I'm thinking that maybe the wet roof shingles in some way reflect radio energy in ways that dry shingles don't reflect them, causing either less energy to be present at the antenna or causing multipath that affects the tuner's ability to lock on.

Anyone?

TH

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JohnS-MI

· #2 · May 13, 2006

Directionally, I think it has to increase reflection at the shingle surface, and increase absorbtion through the shingle, both lowering transmission through the shingle.

But I don't know how to calculate whether either would be very significant at uhf frequencies.

At somewhat higher GPS frequencies (and more marginal signal strength) my roof always wipes out reception (sometimes right by a window it can see enough satellites.)

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Dibenzylacetone

· #3 · May 13, 2006

Water does a pretty good job of absorbing UHF and microwave electromagnetic waves. As such, Have you ever noticed that satellite antenna installers always avoid having trees in between the dish and the satellite? Well, there's a lot of water in those layers of leaves - and of course, in the trunk and branches - and it plays havoc with reception. So, wet roofing tiles decrease the signal more than dry roofing tiles. Also, since there's a lot of moisture in an attic, the joists and sheathing tend to absorb more UHF than they would if this wood were in a dryer environment. Kind of sucks doesn't it? But that's why roof mounting works a lot better - not to mention the benefits of the additional antenna height

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