[Elecraft] Problem with 17m band in K2 + KAT100/KPA100 in EC2

[Don Wilhelm]

Marcin,

I checked the RigExpert specifications, and while they claim isolation on
the soundcard connections, they do not make any such claims for the digital
connections (to the PTT, CW Key, or AUX I/O).

So you still may have a problem with RF getting onto the RigExpert or the
computer chassis ground that is being then transmitted into the K2.

This is not a problem with your connections, but it may be a problem with
the RigExpert on your K2 in combination with your antenna situation.  I am
not yet convinced that it is a KPA100 problem.

If you can test it with the KPA100 working into a dummy load, that would be
of interest, but it may be hard to detect if your receive is desensitized
with the dummy load connected.

If you do not have the K2 mic jack shell grounded, you could try doing that
as a first measure of defense.

The other thing you can try is attaching a counterpoise wire cut for a
quarterwave on 17 meters to the KAT100 ground.  The far end may carry a high
RF voltage, so keep it clear of human and pet contact (the far end connects
to nothing - just an insulator).  If a counterpoise wire corrects the
problem then you can be certain it is caused by stray RF - unfortunately, if
it does not cure it, stray RF could still be the problem, but it is worth a
try - a piece of wire an electrical quarterwavelength on 17 meters is
approximately 3.9 meters long.

73,
Don W3FPR


> -----Original Message-----
>
> Thank you for patience and fast replays.
>
> As my digital interface I'm using RigExpert and cable connection as on
> the www.mixw.net/RigExpert/cable-elecraft-001.gif
> After received your last reply I have been examined cable connections
> and they are as on the diagram.
> I have been checked RigExpert and K2 with my laptop computer also -
> the problem also occurred. It means that my home computer is OK.
> But there is interesting thing - when I setup  10W (KPA100 is still in
> bypass mode) there is no problem, but when I setup 11W or more (KPA100
> is on) problem occur.
> So maybe the problem is somewhere in KPA100?
>
> 73,
>
> Marcin SQ2AF
>
> K2 #5408
>
>
> 2006/9/8, Don Wilhelm <w3fpr at earthlink.net>:
> > Marcin,
> >
> > As a guess, your computer connections or even the computer itself may be
> > picking up RF.
> >
> > Are you listening to the audio on the K2 speaker, or just
> observing it on
> > the computer display (or listening to it on the computer
> speakers?  If you
> > are seeing the drop in audio only on the computer, it may be
> the computer at
> > fault and not the K2.
> >
> > If you do not have ground isolation between your computer and
> the K2, that
> > may be necessary.  That means transformers in the audio lines to the
> > soundcard and an optoisolator in the RTS to PTT line.  Be
> careful about how
> > the optoisolator is powered so you do not negate the careful grounding
> > isolation that you would do otherwise.
> >
> > There is a good schematic for proper isolation of the computer and
> > transceiver grounds in Jan 2006 QST, page 60 (you need only consider the
> > part in the shaded box).  Note carefully the grounding to the
> enclosure does
> > not extend to the computer - if you have jacks for the
> soundcard connections
> > mounted on a metallic box, that would destroy the ground isolation - you
> > must either avoid audio jacks at the enclosure or if jacks are
> used, they
> > must be mounted on an insulator.
> >
> > 73,
> > Don W3FPR
> >
> >
> > > -----Original Message-----
> > >
> > > Don,
> > >
> > > Today I have checked all connections in KPA100 T-R switch -
> they was OK.
> > > After connection checking I assembled KPA100/KAT100 again and started
> > > TX on 17 m again - the problem still occurred.
> > > But .... as you know I'm digi modes fan so, all the TRX keying was
> > > made by computer. Today, when I have been use VOX or foot switch the
> > > problem disappeared!
> > > In this moment I know, the problem occurs only when computer
> > > control K2 keying.
> > > So, it clears why TUNE coming back RX to normal sensitivity.
> > > Do you know what can I do now?
> > >
> > > 73,
> > > Marcin SQ2AF
> > >
> > > K2 #5408
> > >
> > >
> >
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