Kelly, the problem is that the panels are screwed (best) or nailed into boards
or plywood below. With temperature changes the metal sheets or panels change
and the fastener becomes a diode junction if the metals are dissimilar.
Generally it is not the roof panels that cause the problem if they are all the
same, it will be the fasteners and corrosion. Gutters and downspouts with
dissimilar screws are also a problem. Avoid copper and galvanized material
contact as they be a real problem.
73,
Gary ~ AB9M
Sent via the Samsung Galaxy Tab® 3 Lite
-------- Original message --------
From: Kelly Taylor
Date:01/11/2018 1:31 PM (GMT-06:00)
To: GARY HUBER
Subject: Re: [TowerTalk] Metal Roof
If you don’t want to replace the roof, how about a portable spot welder?
73, kelly, ve4xt
> On Jan 11, 2018, at 1:29 PM, GARY HUBER <glhuber@msn.com> wrote:
>
> I agree with Jim as I ran into the same problem at work. Twelve story office
> building with a copper roof. Any two meter transmission at that building roof
> area over two Watts and intermod products would cause problems in other VHF
> repeaters several blocks away. Our solution was split site, with the TX on
> another 12 story plus engineering floor on top.
>
> Bonding the roof can be done... the problem is dissimilar metals in the roof
> panels and fasteners plus lack of a sealant to keep the screw - panel
> junction dry. There is another way to fix the problem... slate or tile roof
> heavy enough to resist the wind problem.
>
> 73,
> Gary ~ AB9M
>
>
>
> Sent via the Samsung Galaxy Tab® 3 Lite
>
>
> -------- Original message --------
> From: Jim Brown
> Date:01/11/2018 1:00 PM (GMT-06:00)
> To: towertalk@contesting.com
> Subject: Re: [TowerTalk] Metal Roof
>
> Hi Skip,
>
> The "interference" is probably passive intermod (rectification at one or
> more joints in that roof) that is generating a spur on the input
> frequency of the repeater. If this is the cause, the joint(s) must be
> bonded at multiple points.
>
> 73, Jim K9YC
>
> On 1/11/2018 10:29 AM, Gilbert Kauffmann wrote:
>> My repeater is desensed.
>
>
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