[TowerTalk] Grounding of cables to tower?

[Wes Stewart]

On 10/18/2017 3:34 PM, Jim Brown wrote:
> On 10/18/2017 1:47 PM, Wes Stewart wrote:
>> A couple of questions:
>>
>> 1) on page 15 of your referenced document you say a distant tower should not 
>> be bonded to house (shack) ground and go on to connect the coax shield.  How 
>> is that not a connection between the two?
>
> It is a connection at DC. But at RF, the inductance of that connection 
> dominates, so it's not a bond --  a bond must be a low impedance connection.   :)

The NEC says of bonding in Article 100: "The permanent joining of metal parts 
together to form an electrically conductive path that has the capacity to 
conduct safely any fault current likely to be imposed on it."  By this 
definition, the coax shield is a bonding conductor.  You're making stuff up.
>
>> 2) Where does 200' come from?
>
> A poorly chosen, too conservative number. In editorial discussions with Ward 
> in the process of reviewing his book, we sort of agreed that 60-100 ft was 
> better.

That's almost 3 dB different.  I agree that there has to be some number, 
otherwise, your tower would have to be bonded to my building ground, but I'm not 
sure an "editorial discussion" is convincing without supporting evidence.
>
> Another point that I should have made is that if mains power is fed to the 
> tower, the green wire must, by code, be run with the phase and neutral 
> conductors, and it should be bonded to ground at the tower. The reason is what 
> Jim Lux articulated earlier in this thread (or maybe another thread) -- the 
> bond must be there so that a fuse or breaker blows in the case of a fault from 
> phase to ground.
>
> Thanks for catching the conflict -- I'll have to change that when I have time.
>
> 73, Jim K9YC
Wes  N7WS