[Elecraft] Power oscillation problem (KPA500+KAT500)

[Andy Durbin]

I followed up on the RFI theory and quickly found a solution to the problem.

My TS-590S has a homebrew breakout box on the REMOTE connector.  This breakout box provides key line level shift and key line interrupt for my SteppIR.  The TS-590S ALC control line is on this cable but is not terminated in the breakout box.

I disconnected the REMOTE connector from the TS-590S and arranged for direct local keying of the KPA500.  This eliminated a possible path for RF entry to TS-590S (and also KAT500 and KPA500).

In this configuration I was able to output over 400 W on 7.01 MHz with no oscillation present.  With the breakout box connected oscillation was present with power greater that 108 W.

I should be able to fix the problem with better decoupling and/or choking of the breakout box connections.

Thanks to everyone for the suggestions and comments.

73,
Andy, k3wyc