[Elecraft] K3 powers off when after several minutes of 12W carrier

[john at kk9a.com]

Instead of pushing the 12 watt PA this hard it would sure be nice (and
cleaner) to have the option of using the KPA3A for 10-12 watts output.

John KK9A


K7TV wrote:

I have been testing sustained power capabilities of wideband HF transformers
for feeding EFHW antennas. This involves running high power through HF
transformers back to back into a dummy load. When running 200W out of the
KPA500, the K3 was indicating 12W, and I think that means the 100W PA was
not operating. After a few minutes the K3 totally shut down. This had
nothing to do with the transformers under test; I get the same result when
running the KPA500 at 200W directly into the dummy load. After restart the
K3 shows no sign of problem unless the 200W endurance test is run again.
Then I increased power just a little bit so that the 100W stage kicked in. I
got 300W out of the KPA500, and now the K3 keeps going without shutting
down. I can see how 12W may be a bit much for the driver stage, but if so,
shouldn't the 100W stage kick in sooner? Also, I expected the K3/KPA500
combo to be able to produce any power level I wanted within its range. What
I see is that when the 100W stage kicks in, the output (as seen on an analog
meter) makes a big jump so that certain power levels cannot be achieved.

Thanks,
Erik K7TV