[Elecraft] KAP1500 High SWR wen unkeying with FT8

[Andy Durbin]

I had a problem with high SWR when unkeying a TS-590S used with KAT500 and KPA500.  It was a challenging investigation.

I found that, due to the failure of an electrolytic capacitor,  my TS-590 was emitting a short burst of RF on a completely spurious frequency when it was unkeyed.  The failed capacitor changed the rise time of a TX/RX switching signal and resulted in an unintended oscillatory loop.

The spurious frequency was way off the frequency to which my antenna was tuned so I received a high SWR indication.

I'd suggest you use appropriate tools to examine the frequency of the amplifier RF drive signal for the TX/RX transition.

73,
Andy, k3wyc