[TowerTalk] Fwd: Fwd: Antenna to Shack Ground Connection

[Hans Hammarquist via TowerTalk]

I hope we don't get a flame from this.


By connecting the shack and all equipment to the tower you want to, as much as possible, putting your shack on the same voltage potential as the tower. Ideally at a direct strike, the shack and the tower will have no (or almost no) voltage between them. With no voltage difference you will have no current.


Needless to say, in order to accomplish this the connection between your tower and shack has to be of enough size not to fuse at a strike. A couple of 3/4" Cu pipes will sustain most strikes. I don't know if a #4 wire will do. (I am using a 6" wide piece of sheet aluminum.)


At the shack, the Al strip is connected to a steel plate where all cables, telephone, control, coax etc are going through, entering the shack. This plate is connect to a shield/screen that surround the shack. (I installed a shield consisting or #20 wires and aluminum foils around the shack when I built it.)


I would think that if you place a metal sheet just under the table-top where your equipment is located, your equipment should be relatively well protected if the plate is connected to the tower.


There are many ways to protect your shack but trying to isolate it by not connecting it to the tower will result in the current from a strike will follow whatever cable/wire you have between the tower and your shack resulting in ..., no I don't have to elaborate on that. A grounding rod have, at best, a few ohms resistance to ground. A direct hit generate currents in the order of 1000 amps or more. Say, you have 2 ohms resistance in your ground systems you will get about 4 kV difference (2+2)*1000, enough to do a lot of damage.




 

-----Original Message-----
From: Bill Turner <dezrat at outlook.com>
To: Towertalk <towertalk at contesting.com>
Sent: Fri, Jan 30, 2015 9:22 am
Subject: Re: [TowerTalk] Fwd:  Antenna to Shack Ground Connection


At the risk of starting a flame war (wouldn't be the first time), I
have to question the purpose of running a ground wire from the tower
to the shack.

What is it you are trying to accomplish?  Or putting it another way,
what current are you expecting to flow between your tower and your
shack?

If your tower takes a direct lightning strike, won't a small
percentage of the strike find its way into this ground wire, and since
the wire to earth connection is not zero ohms, some of the strike will
find its way into your shack?  

Even if you disconnect your coax and rotator cables during a storm,
this ground wire leaves your shack vulnerable, doesn't it?

Does not sound good to me but if there is a good reason, I want to
hear it.

Bill W6WRT
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