Tom,
If your running your 590 through a final amplifier, you might check the
antenna relay in the amp. I had trouble with my old als600 amp right after
I got it and I had to adjust the antenna relay contacts and clean them so
that my receive would always come back. Just recently I started getting
strange swr readings when transmitting with high power with my ALS1300 amp.
I found that the output coax connector had gotten slightly loose on the
chassis and after tightening the nut holding the connector to the chassis,
problem solved.
Bob, K8LR, [log in to unmask]