[Elecraft] OT - anyone have experience with effects of metal roofs on antenna performace?

[WILLIS COOKE]

Paul, I doubt that anyone can predict the effect exactly without some very sophisticated modeling software and exact dimensions.  I will give a stab at it, but because you are talking about a very wide frequency band and some unknowns about bonding and the conductivity of the roof you will have as an alternate I will have to speak in generalities.

Since you are talking 30 feet from the antenna which is about 1/2 wavelength on 20 meters, presumed to be the lowest frequency, the effect should not be too great.

The alternate roofing material will also affect radiation somewhat, so I would doubt that the solid metel effect would be much greater than composition shingles.  I don't know much about ceramic roofs, but I would guess they would have a little greater effect than composition but less than metal.  

I would expect more effect on pattern than SWR or other loading indications.  The effect, if noticed at all would be a slight signal improvement in the directions away from the room and a slight deterioration in the direction of the roof.

I would expect that your situation will be very interesting for observation and discussion during rag chews and increase your enjoyment of your QTH and amateur radio.  We hams like to observe and discuss such things at length.  I would predict that you are much more likely to make interesting contacts while sitting in a dry hamshack talking on the radio than while replacing shingles standing on the roof.  My advice as an Electrical Engineer and after 57 years as a ham radio operator is to buy the roof you want, enjoy the lack of leaks and continue to enjoy radio.  I doubt that you will notice much difference in antenna performance, but you will spend many enjoyable hours trying and discussing the difference on the radio and in eyeball QSOs.
 
Willis 'Cookie' Cooke 
K5EWJ & Trustee N5BPS, USS Cavalla, USS Stewart


________________________________
 From: Paul Taenzer <ptaenzer at gmail.com>
To: elecraft at mailman.qth.net 
Sent: Thursday, July 4, 2013 11:19 AM
Subject: [Elecraft] OT - anyone have experience with effects of metal roofs on antenna performace?
 

Hello,

We live on a very windy Island (with an industrial wind farm) and have been
loosing shingles off the roof due to severe wind storms.

We've been considering having a metal roof, but I'm wondering about the
possible impact of the metal roof on the radiation pattern and efficacy of
nearby antennas.

There's a SteppIR on a tower about 20 feet from a corner of the roof. The
antenna is about 30 feet higher than the highest point of the roof.

I'd appreciate learning from anyone with relevant experience or technical
expertise related to this.

Many thanks.

73s,

Paul
VA3LX
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