[Lowfer] 2200m problem found

[Brian, WA1ZMS]

I'm happy to say that my issue was in fact a corona induced failure.  Thanks to all for your comments.

Now the details.....
Punch line: It was a classic 'ZMS design failure in the waiting!! :- )


In order to switch between LF/MF and  HF in the shack with just the one common antenna, I had placed a large industrial contactor in a WX proof box where the open wire feeder comes to the side of the house.  The contactor allowed me to switch the open wire feeder to either an HF balun or to a single binding post for LF/MF use and to the variometer mounted below.  All was fine for years until I went QRO on 2200m.  The insulating frame of the contactor now has blister marks all over it. Rather impressive if I may say so myself.  The insulating frame of the contactor had the full LF RF voltage on it and it must have been glowing purple inside the box.

Now....I have a spare to replace it. I guess going forward I must simply go outside and manually strap the connections if running QRO on 2200m.

My quick circuit simulation today showed about 10kV of RF at that node with only 100w. So I am suprised it even functioned originally  at that power level during the winter. Maybe it was already breaking down and the extra RF finished it off but good.   An interesting problem to solve if I wanted the ideal design.  I'm not so sure a set of vacuum relays would be up to the task, but maybe. I need to go look at some specs.  I'm open to other ideas if anyone has any.

-Brian, WA1ZMS
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