[Elecraft] Strange KPA500 problem on 6M

[Carl Yaffey]

Bottom line: I can’t get more than 200 watts out of my new KPA500 on 6M. It faults (HI SWR FAULT) when I try to increase the drive in order to get more output.
But I get full power on 6 with a dummy load.

Bad antenna? Don’t think so. Here’s my setup:
3 element M2 6M beam fed with high cost, low loss coax. Very low SWR and works great until I try to get more than 200 watts out of the amp.
I also have an R8 vertical and an HF dipole, both of which tune up on 6 with my new KAT500.
When running the amp at 200 watts, the swr indicator shows low swr with the KAT500 and any of the 3 antennas. As soon as I increase the drive with any of the 3 antennas, I get the fault.
When running the amp without the KAT and the beam hooked directly in, same fault when increasing drive.

The beam looks good in an MFJ antenna analyzer as does the R8.

So, I think the amp must be extremely sensitive to anything other than a pure 1:1 load as provided by the dummy load.
Your thoughts?
Carl, K8NU



Carl Yaffey K8NU

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