Just really lucky maybe but I roof mounted a Hy-Gain Hy-Tower multi-band
vertical on the middle of the roof of an all metal barn which is about
36x72 ft and about 18 1/2 ft tall at the eaves with a low pitch gable
roof 2.5:12 pitch. It has been up for going on 4 years and gets a lot
of complements from the net controls of the nets I frequent. It is
roughly equivalent in performance to my Carolina Windom which is about
90 ft on one side, 180 on the other and is fairly horizontal at about
40 ft.
The barn is about 45-50 years old and I replaced many of the screws
securing the steel roof panels shortly after the turn of the century
(2000 not 1900.) Subsequently I welded on several lengths of 2 3/8 pipe
to make the bld more rigid and had it moved a quarter mile south to a
location more convenient and then put up the vertical. The building has
10 each steel tube columns, five to a side which connect to steel
reinforced concrete piers (think Ufer ground.)
So far I have observed no problems and really like the multi-band
performance. I'm anxious to see how much better the SteppIR DB42 up
about 75 feet turns out to be. This vertical will remain as a good
backup antenna.
I had initial concerns and was warned by a few folks about all the
terrible things that would happen. So far as I can check, none of these
things have happened. I did do a 4-way Phillystran guy instead of
having to super reinforce the roof to take the forces that would be
present at the base of the free standing tower as designed to be mounted
to a cubic yard of concrete in the ground.
Patrick NJ5G
On 3/2/2016 7:29 AM, Hans Hammarquist via TowerTalk wrote:
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.>> _________________> Topband Reflector Archives -
http://www.contesting.com/_topband>______________________________________________________________________________________________TowerTalk mailing
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