[TowerTalk] RF Surge Suppressor at Base of Tower or Shack SPG or Both ?

[Gene Smar]

Shawn:

      My antenna/coax configuration is a bit different in that I have an 
antenna switch at the bottom of the tower.  All of my HF antenna coax 
lines terminate on that switch before an antenna is selected and passed 
on to the shack's coax line.  So all of these lines go through 
Polyphasers before they hit the switch.  In that way even the 
non-selected antennas/coax lines are protected.  I do not have a surge 
arrestor on the coax line from the switch to the shack. My thinking is 
it's entirety is underground for about 50 feet and the likelihood of an 
induced current on the shield is negligible.  (I expect some 
disagreement on this.)

      However, the commercial practice is to place arrestors at the 
building/shack entrance, on a single-point ground panel that is 
connected to the earthing system.  No arrestor is placed where the coax 
leaves the tower; only the shield is grounded at that spot. Therefore, I 
would recommend installing the arrestors at the shack entrance.  If you 
have a legal copy of Motorola's R56, refer to the figures on page 7-42 
for a pictorial.


73 de
Gene Smar  AD3F


On 10/12/2021 6:44 PM, Keith Dutson wrote:
>   Shack entry only.
> 73, Keith NM5G
>      On Tuesday, October 12, 2021, 04:28:48 PM CDT, Jim Brown <jim at audiosystemsgroup.com> wrote:
>   
>   On 10/12/2021 11:14 AM, Shawn Donley wrote:
>> Where should the coax surge suppressors go?  At the base of the tower or at the shack entry box or both?
> Where antennas are bonded to all the bonded grounds, where they enter
> the shack. They protect the rig(s) two ways. First, by bonding the coax
> shield, and second by shorting the center conductor to that ground.
>
> The coax shield should be bonded to the tower at top and bottom, but an
> arrestor at the tower is a waste of money.
>
> Remembering that lightning is an RF event, not a DC event, a 130 ft long
> bonding wire looks like an inductor, and is essentially a waste of
> copper. It's only required if you have mains power at the tower, in
> which case it must be run with the power conductors (as with Romex, or
> in conduit).
>
> The N0AX book is a great reference, to which I contributed.
>
> 73, Jim K9YC
>
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