[Elecraft] KPA1500 PA Current

[Andy Durbin]

"Have you considered that there may be something in your antenna system that is heating up or otherwise changing with the 1500 watts power? The first thing I would suspect is a balun that is heating, or a connector that is not quite tight enough."

After years in lab and flight test I came to appreciate the value of good instrumentation.   The data below is a case of SWR run-away believed to be caused by heating of a mix 31 choke when an antenna matched for 160 m was used on 80m.  The rapid but progressive rise in SWR is very different from what would be expected for an arc-over event.  This data log shows parameters reported by my KAT500.  The final two events are the KAT500 faulting and opening the KPA500 key line.

2019-02-21 06:56:02	New VSWR  - VSWR 1.06;
2019-02-21 06:56:02	New VSWR  - VSWR 1.00;
2019-02-21 06:56:02	New VSWR  - VSWR 1.08;
2019-02-21 06:56:02	New VSWR  - VSWR 1.07;
2019-02-21 06:56:03	New VSWR  - VSWR 1.05;
2019-02-21 06:56:03	New VSWR  - VSWR 1.08;
2019-02-21 06:56:03	New VSWR  - VSWR 1.15;
2019-02-21 06:56:05	New VSWR  - VSWR 1.19;
2019-02-21 06:56:05	New VSWR  - VSWR 1.25;
2019-02-21 06:56:05	New VSWR  - VSWR 1.30;
2019-02-21 06:56:05	New VSWR  - VSWR 1.38;
2019-02-21 06:56:05	New VSWR  - VSWR 1.44;
2019-02-21 06:56:05	New VSWR  - VSWR 1.49;
2019-02-21 06:56:06	New VSWR  - VSWR 1.58;
2019-02-21 06:56:06	New VSWR  - VSWR 1.72;
2019-02-21 06:56:06	New VSWR  - VSWR 1.85;
2019-02-21 06:56:06	New VSWR  - VSWR 1.90;
2019-02-21 06:56:07	New VSWR  - VSWR 2.00;
2019-02-21 06:56:07	New FLT  - FLT4;
2019-02-21 06:56:07	New AMPI  - AMPI1;

73,
Andy, k3wyc