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Re: [TowerTalk] Metal roofs and EMI/RFI

To: Jim Hoge <>, towertalk <>
Subject: Re: [TowerTalk] Metal roofs and EMI/RFI
From: Grant Saviers <>
Date: Sat, 06 Aug 2011 09:02:23 -0700
List-post: <">>
I've had two verticals on metal roofs, old galvanized barn and shed 
roofs at that.  A 80m hat loaded 40' vertical was terrific for DX, 
particularly when using a Beveridge or dipole for lower noise receive.  
An elevated vertical with a large metal ground plane is an excellent DX 
antenna IMHO.

The antenna support structure, connectors, and coax PIM (passive 
intermodulation) issues are an issue on cell towers with lots of full 
duplex radios, but I think unlikely in common amateur service.  Anyway,  
you likely have many thousands of metal to metal joints in RG8 shields, 
metal fences, tower parts, house wiring, audio systems, etc. etc.    
There is an interesting application note from Andrews that compares 
braid coax PIM with hardline, as an example.


On 8/5/2011 10:57 AM, Jim Hoge wrote:
> Are there any RF noise issues to consider when contemplating a residential
> reroof from composition to metal shingles? The last thing I want to do is
> increase my background noise level here in suburbia.
> Tnx, Jim W5QM
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