[TowerTalk] Common ground, different electrical feeds Frying antennas and finals

[Roger (K8RI) on TT]

I've mentioned this before, but so far No luck.
My shop and house are on adjacent lots. They have separate electrical 
services.  I wanted to back feed the shop from the house, but the 
inspector wouldn't go for it.
So I have two stations set up for SO-2R using the same antenna system.

The coax shields and the antenna grounding system ties the building 
grounds together.  I can see no way of avoiding that without eliminating 
the SO2R setup, but I don't have room, or the budget for two complete 
antenna systems.  Sure, I could eliminate the physical grounds at the 
rigs, but the coax still ties them together.

Now I need to find the grounding problem as the antenna system ground 
ties all the rigs to a common ground, yet they are on different 
electrical feeds.  I've fried Two of the big 144/440 antennas. 1 Diamond 
and one Comet, plus one Comet (IIRC) took a direct lightening hit.  The 
end element looks like it's 1/8th inch brass rod.  After the strike it 
was about 8 or 10 inches shorter, and looked like a half used brazing 
rod.  I've also fried the finals in a pair of 2-meter rigs. I have the 
same rigs and antennas in the house and nary a problem.  I'm fairly sure 
it was not lightening that took out the antennas and finals.  Finals and 
antennas did not fail at the same time.

Lightening, I can't do much about, but the common ground...I'm not sure 
if there is any way to isolate them due to the coax shields and the 
grounding system.

There are 2 towers and 2 masts with verticals on them.  They are all 
tied to over 600 feet of bare #2 and 32, or 33 8' ground rods and a 
common point ground at each building entrance for the antennas.  The 
problem may be one of the big 12 VDC power supplies.  I've not been able 
to find anything amiss.

It all worked great until the bees built a nest in the AV-640 matching 
network. I "cleaned" the bee goo out, replaced the connectors and 
rewound the baluns.  It worked fine for a couple of weeks but then The 
antenna seemed to lose most of the resonant points.  A VNA does not 
appear to see a multi band antenna.  A new antenna has the same 
problem.  IOW, it doesn't make sense.  The antenna worked great!  Then, 
it quit as did other similar antennas, and the matching networks in the 
VHF antennas were fried as were the VHF finals in a pair of dual band rigs.

Near as I can tell, I'm going to have to set up a log, and proceed step 
by step.

This has gotten difficult as I can only work with one hand so it takes 
me a lot longer to work, step by step.  and I've not been able to 
isolate it to one building, just the antennas...I think.  IOW, I'm not 
sure about much of anything at this point.

-- 

73

Roger (K8RI)