[TowerTalk] Grounding a metal roof/Direct TV

[Grant Saviers]

Code requires everything in a metal building to be grounded, extra 
ground wires to the structural steel from the service entrance ground, 
all plumbing grounded to same, etc.  There is nothing special for the 
skin or roof, but there are thousands of screws doing the grounding to 
the girts and purlins.  So IMHO there is no safety reason to not ground 
the roof.

I know from cell phone reception experience a metal building is a very 
good approximation of a Faraday cage - 3 bars outside, none inside.  I 
had to add a Wilson amplifier and external antenna.  If your roof edge 
to ground rod wires are frequent enough around the perimeter that may 
help keep strike current away from the house contents.  A foundation 
perimeter ground wire with periodic rods and/or Ufer grounds in footings 
add another layer of protection.

It sounds like your building is fairly recent, so if you have a Ufer 
ground in the footings (should be near the service entrance panel/meter 
and be visible or have a inspection hatch)  that is another good 
grounding point.

Grant KZ1W

On 12/27/2011 3:47 PM, Cqtestk4xs at aol.com wrote:
> I'm still doing the ground work to get my station up and  running.  Right
> now I'm taking care of the grounding situation....pretty  important in the
> lightning capitol of the US.
>
> I'm doing the usual...grounding the bulkhead, everything to a  common
> ground , Polyphasers etc.  One unusual aspect of my station is  I have a metal
> roof, actually two of them.  A cupola, and then down below  that is the main
> metal roof.  It would take some time, but it would not be  a big deal to
> ground the cupola to the main roof and then ground the roof to  main ground
> where the telco/power company ground located and tied to the  bulkhead.
>
> The roof is a standing seam type so oxidation from weathering on  the
> screws won't be an issue.  There are thousands of screws holding the  thing
> together so I can't do any kind of retrofit or anything like that.   Just a
> stainless screw with a stainless washer holding the braid to a panel and  then
> down to the ground.
>
> Anybody out there with some technical info on whether the grounding  is
> necessary to keep the roof at the same potential to everything  else.
>
> Also before I even got any towers up last summer, we got nailed  with a
> lightning hit that came through the Direct TV and took out our 60 inch  screen
> which was two days old.  Any place to get a Polyphaser for this that  won't
> break the bank?  I believe Direct uses around 1.2 gHz.
>
> As always thanks for the help.  I bet I get a usable answer in  an
> hour...always happens!
>
> Bill K4XS
>
>
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