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

[Don Wilhelm]

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
>
>