[Elecraft] Fwd: Re: KPA 500 rfi problem and other curious behavior

[Ron D'Eau Claire]

The first step, if you haven't done it already, is to connect the KPA500 to
a good dummy load and test it on 80 meters. That eliminates a problem in the
80 meter bandpass filter in the KPA500. 

You can run the KPA300 without the AUX cable (See Fig 3 in the KPA500
Owner's Manual) to test your theory about that being where the RF is getting
in.

73, Ron AC7AC 



-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Robert Redmon
Sent: Thursday, October 24, 2013 4:32 PM
To: elecraft at mailman.qth.net
Subject: [Elecraft] Fwd: Re: KPA 500 rfi problem and other curious behavior

In addition to the display problem on 30 meters described in a previous
post, I have never been able to use the KPA 500 on 80 meters. If I run the
K3 at 100 watts, the swr shows very low (below 1.3:1) and is consistent. If
I put the KPA500 in line, it faults with "high swr" as low as 75 watts
displayed on the KPA's display. Also,the swr changes as I transmit, randomly
spiking up to full scale and shutting the amp down. 
It does this with even more frequency at higher power. I have eliminated as
many other variables as possible and have come to the conclusion that on 80
meters (only....apparently) enough rf makes its way into the
KPA500 to cause this behavior (even at very low power). The antenna is a
shunt fed tower, fed with buried hard line about 100 feet from the shack. I
feed the same tower (same feedline) on 160 without issue.

My instincts tell me the ingress point is the AUX cable (the one thing I
haven't tested), but I am otherwise at wit's end. Anyone have any
suggestions?

Bob

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