[TowerTalk] Grounding mast?

Roger (K8RI) K8RI-on-TowerTalk at tm.net
Wed Jul 30 16:08:45 EDT 2008

hdmc38 at bellsouth.net wrote:
> Jim 
>  NEC Chapter 8 requires a separate ground from the mast, down the tower to the ground rod. Since the mast is above the rotor that's where it is connected. I'm not saying it works better or worse.Sure can't hurt. I've had my SPG set up this way for 5 years never a problem.YET! Hope this helps.
It certainly would not be a bad idea but that would be an interesting 
proposition as a good electrical ground would be heavy enough to create 
problems when turning the mast. Nor would you be able to use rotator 
loops in the normal sense without defeating the purpose of the ground. A 
two or three turn loop at the top of the tower or around the rotator 
would create enough inductance to act as a choke, effectively creating a 
high enough impedance and reverse EMF to cause the lightning to jump 
around it to the tower, or what ever was near.  I'd certainly not want 
the loop around the rotator due to the magnetic field.

My question then is how do you attach a bare #2 or 4 copper wire to the 
mast above the top of the tower and allow for 540 degrees of turning. In 
my case all antennas are grounded, the pigtails are grounded at the top 
of the tower and the coax is grounded at the base, BUT each coax has a 3 
turn loop at the top of the tower (laying on the top plate). OTOH the 
braid would not be considered heavy enough for a ground any way, nor 
would a braid "up there". Even if I used some of the woven copper cable 
used for lightning rods there is still all that extra length to allow 
for the rotation.

Practical experience has shown me that will all the lightning strikes my 
system has taken that this shouldn't be necessary, but I readily admit  
even all those strikes are not enough to come any where near being a 
valid statistical analysis.

Roger (K8RI - ARRL Life Member)
N833R (World's oldest Debonair)

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