[Elecraft] KPA500 RFI problem

[Jim Miller]

I strongly suspect you have a common mode problem. These can be very
frequency dependent.

Read: http://audiosystemsgroup.com/RFI-Ham.pdf especially the section on
common mode chokes. There is a cookbook near the end for band specific
chokes.

For more details on the math read:
http://fermi.la.asu.edu/w9cf/articles/balun.pdf

I'd also recommend you take out the 4:1 transformer.

Good luck

jim ab3cv

On Tue, Jan 8, 2013 at 8:06 PM, Ron W3ZV <w3zv at verizon.net> wrote:

> At least I'm pretty sure its an RFI problem. I have a K3, KAT500 and the
> KPA500 connected as recommended with Elecraft DB15HD cables. The antenna is
> a 120ft. doublet fed with ladder line to a 4:1 balun and 10ft of coax to
> the KAT500. I have a comment point ground to a ground rod six foot from the
> shack. I have operated the amp at 400+ watts from 80m to 6m. The only band
> that gives me a problem is 12m. When I am operating at 400 watts ssb, the
> amp will fault with a high swr indication within 5 to 20 seconds.
> Immediately prior to the fault the swr on the amp display was 1.2:1.
> Reducing power to below 300 watts seems to avoid the problem.
>
> Assuming the consensus is that this is RFI, what would be the most likely
> suspect? Coax cables in/out? DB15HD cable? Power cable? What's the easiest
> way to diagnose and correct the problem? Thanks
>
> Ron W3ZV
>
>
>
>
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