[Elecraft] KPA500 RFI problem

[David Gilbert]

He said that his SWR on 12m was already low, so I don't see how that 
helps a lot.

Dave   AB7E


On 1/8/2013 6:40 PM, Rick Bates wrote:
> Try altering your feedline length (which means resetting the KAT500 memories
> too).  I had a similar issue on 80M.
>
> However in my case, it made no difference when I added 30' more window line
> but changing the coax length (+~30') allowed it to load.  The doublet length
> is 170' per side (all HOA stealthy too).
>
> I use a 10 KW rated DX Engineering 1:1 common mode choke to convert window
> line to coax AND keep RF outside the shack.  Their website has a 'white
> paper' comparing 1:1 and 4:1 which is worth reading too.
>
> 73,
>
> Rick wa6nhc
>
> -----Original Message-----
> From: Ron W3ZV
>
> 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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