[Elecraft] K3/KPA500/KAT500 SWR problem

[Robert Redmon]

FWIW, Although I don't have the KAT500, I have found my KPA500 to be 
very, very sensitive to rf on the feedline, especially on 80 and 40 
meters. I have checked, rechecked everything (connectors, feedline, 
switches, etc.) and tried adding various common mode filters, changing 
feedline length, etc. over a period of 2 years now and still have not 
resolved the issue. I disassembled my KPA500 and checked all the chassis 
grounds, making sure all was tight and no paint was interfering with the 
rf integrity of the case. That did produce some improvement, but the 
problem persists. In my case, the random swr spike and (occasional) 
resulting fault always occur during the first microseconds of a 
transmission.  Though Elecraft support has worked with me to try to 
resolve this issue, so far it has no yielded to our efforts. This does 
not occur when I transmit into a dummy load, either in the shack or at 
the tower.  Though my experience isn't the same as is being discussed 
here, I suspect the root cause may be similar.

Bob K5SM