The problem using a metal roof as a ground plane is the possibility of
rectification between the seams. The current will not be even across the seams
and if (possibly more:" When ,,,") there is a bad connection at that point you
might risk a rectification that will generate harmonics with possible RFI
problems.
I would test it but would be very alert regarding harmonics.
Good luck with your installation and best 73 de,
Hans - N2JFS
-----Original Message-----
From: Brad Rehm <bradrehm@gmail.com>
To: Douglas Ruz (CO8DM) <co8dm@frcuba.co.cu>
Cc: towertalk <towertalk@contesting.com>; topband <topband@contesting.com>
Sent: Wed, Mar 2, 2016 9:12 am
Subject: Re: [TowerTalk] Topband: Ground screen ????
Douglas,You certainly can use the galvanized roof as a ground screen. It might
bea good idea to measure resistance between sheets to get an idea of how
wellthey're all tied together electrically. If they're not, you might see
someodd shifts in VSWR when you send RF through it. Another potential
problemis that RF may be coupled into the building wiring when you transmit.
Thisis why you'll want to bring grounds up to the roof in as many places as
youcan.But heck, try it! Hams have made stranger things work as
antennas.73,Brad KV5VOn Tue, Mar 1, 2016 at 9:09 PM, Douglas Ruz (CO8DM)
<co8dm@frcuba.co.cu>wrote:> Hi,>> Need some ideas from your side...>> I am
trying to find a good solution for my 160/80m antenna.>> I am thinking about
some kind of Inv L with an 80m trap as a radiator for> both bands.>> But, what
about the counterpoise...Unfortunately in my small city lot I> can´t install
radials and I can´t get parts for the FCP yet...what about a> Ground screen
???...I have a galvanized roof...it is about 50 ft long and> 16 ft
wide...galvanized sheets are 3 by 8 ft long and all are bolted> together. The
roof is about 15 ft high.>> Can I use this roof as a ground screen for the
160/80m antenna ???>> Thoughts ?,>> 73....Douglas, CO8DM> P.S:1- I finish my 50
ft tower installation.> 2- Thanks for all QSO´s on 160m before ARRL CW
contest with me and> with our contest station T48K.>>
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