[Elecraft] Strange K3 & KPA500 Issues fixed with a longer coax cable?

[Jim Miller]

Your problem isn't the length of the coax between the units. It is RF
getting into the shack in the first place via your feedline. What antennas
and feedlines do you have connected? What sort of common mode chokes have
you applied to the antennas which are connected.

73

jim ab3cv

On Wed, Nov 19, 2014 at 8:19 AM, James kvochick <jameskvochick at me.com>
wrote:

> 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.kaz at 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-bounces at mailman.qth.net] On Behalf Of
> Jim
> > Kvochick
> > Sent: Tuesday, November 18, 2014 9:16 PM
> > To: elecraft at mailman.qth.net
> > Cc: kvo at 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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