Jim, RFI is not the issue here.What is happening is a matter of " Inductance "
By adjusting the length of the Jumper, the Impedance is adjusted accordingly.
((((73)))) Milverton.
From: James kvochick <jameskvoch...@me.com>
To: "N2TK, Tony" <tony....@verizon.net>
Cc: "elecraft@mailman.qth.net" <elecraft@mailman.qth.net>
Sent: Wednesday, November 19, 2014 7:19 AM
Subject: Re: [Elecraft] Strange K3 & KPA500 Issues fixed with a longer coax
cable?
We tried all the normal "common mode" tricks, but the feedline length appeared
to be the most effective.
Jim K8JK
Sent from my iPad
> On Nov 19, 2014, at 7:32 AM, N2TK, Tony <tony....@verizon.net> wrote:
>
> I had a similar problem many years ago with an L-4B amp.
> I wonder if adding ferrite to the coax would solve this problem?
> GL
> N2TK, Tony
>
> -----Original Message-----
> From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Jim
> Kvochick
> Sent: Tuesday, November 18, 2014 9:16 PM
> To: elecraft@mailman.qth.net
> Cc: k...@att.net
> Subject: [Elecraft] Strange K3 & KPA500 Issues fixed with a longer coax
> cable?
>
> I've stumbled into a strange problem.
>
> I have 4 friends with similar K3 stations to my own; K3 >>> KPA500 >>>
> KAT500. The stations are powered with similar power sources.
>
> One station sounds fine, works great. The other 4 had strange issues that
> manifested themselves as audio distortion when running the amplifier. After
> looking all over for RF and grounding issues, we swapped the coax cable from
> the K3 to the amplifier, with a longer cable (about 6 to 7 feet - largely
> because that was the only free cable we had handy).
>
> Making the cable from the K3 to the amplifier longer eliminated the issue.
> putting the cable back brought the problem back. Making a new short cable
> still left us with audio distortion. The only thing that seemed to solve
> the issue in all 4 cases was making the K3 to amplifier cable longer.
>
> This got me to investigate my own station. It turns out that the cable I
> used between the amplifier and the radio was about 6 feet long. Swapping
> this cable for a shorter length brought about audio distortion symptoms.
>
> Does anyone have any thoughts about this?
>
> Cheers
>
> Jim K8JK
>
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