K3/KPA500 occasional high power input

Posted by gi4doh on Nov 03, 2015; 12:08pm
URL: http://elecraft.85.s1.nabble.com/K3-KPA500-occasional-high-power-input-tp7609888.html

With my K3/KPA500/KAT500 combo I occasionally get a soft or hard alarm on the KPA500 due to the K3 briefly giving a high power burst.
I now have a digital peak power meter between the K3 and KPA500 and I can see the surges.
The power output from the K3 is steady apart from these brief bursts. The power will change from typically 25 to 30 watts to anything up to the full 100 watts. The KPA500 gives a soft or hard alarm depending on how high the burst is.
I have tried running into a dummy load and the same thing happens.
These surges are random but they appear to be more frequent on the lower bands - with different antennas and dummy load.
The surges appear to be more likely to occur within a minute or so of changing the power output from the K3 - either up or down.
I run the KPA500 between 400 and 500 watts to achieve 400 watts at the antenna feed point as per UK limits. This means that I also see surges that do not cause an alarm but briefly light the red power LEDs.
I was up to date with all firmware when I last checked about 3 weeks ago.
I have done the Tx power calibration.
Any ideas?
Rich GI4DOH