[TowerTalk] Fwd: Topband: Ground screen ????

[Patrick Greenlee]

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 at gmail.com>
> To: Douglas Ruz (CO8DM) <co8dm at frcuba.co.cu>
> Cc: towertalk <towertalk at contesting.com>; topband <topband at 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 at 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 listTowerTalk at contesting.comhttp://lists.contesting.com/mailman/listinfo/towertalk
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