[Elecraft] KPA500 RFI problem

[Igor Sokolov]

If it is RFI problem (as it was initially suspected) I would first 
disconnect the control cable between K3 and KPA500. I would use only 
separate PTT line to the amd and see if the problem is gone on the affected 
band.

73, Igor UA9CDC

----- Original Message ----- 
From: "Rick Bates" <happymoosephoto at gmail.com>
To: "'David Gilbert'" <xdavid at cis-broadband.com>; <elecraft at mailman.qth.net>
Sent: Thursday, January 10, 2013 1:19 AM
Subject: Re: [Elecraft] KPA500 RFI problem


>I agree that the balun should be checked but that it is likely NOT the 
>issue
> here as it works on the other bands.  If it is replaced, using a 1:1 
> common
> mode choke (not just a voltage balun or series of ferrite cores on the 
> coax)
> would be a good thing to try.  I opted for the 10KW rated version as I 
> never
> want to have an issue and I only run <700 watts.
>
> To make clear an earlier statement of mine, without the added coax, the
> untuned VSWR was 24:1, with the added coax it is under 10:1.  The KAT500
> tuned the wire in both cases here  but in the original configuration tuned
> my EDZ to 1:1 at low power then faulted out at anything above 300 watts.
> Adding more coax solved the issue (I tried a shorter run too, no change) 
> by
> shifting the 80M voltage peak to someplace else on the feed.
>
> Is your wire antenna insulated or bare?  Is there a chance that it is 
> arcing
> (wet tree, mast ???)?  With the voltages produced at QRO, the potential is
> there.  Ditto your window line, insulated or bare?  Is rain or snow
> impacting it?  You'd know because it would need retuning.
>
> Rick wa6nhc
>
> -----Original Message-----
> From: David Gilbert
>
> From a troubleshooting point of view jumping right to the balun
> requires making a lot of assumptions, most of them unwarranted given
> what little we know so far from his post.   More importantly, a balun
> with a ruined core is going to look bad for SWR no matter what power
> level is fed to it, and he says that things look fine at 300 watts but
> go south at 400 watts.  That's an arc over problem somewhere ...
>
> Dave   AB7E
>
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