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

[Rick Bates]

What does it do into a known good dummy load?

If the same, your amp needs to visit the shop. 

If it works with the dummy, it's likely RFI.  Adding a common mode choke at the antenna feed along with improved bonding (grounding) would be the first steps towards resolution of your problem. 

Rick wa6nhc

Tiny iPhone 5 keypad, typos are inevitable

> On Oct 24, 2013, at 4:32 PM, Robert Redmon <k5sm.bob at gmail.com> wrote:
> 
> 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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