[Elecraft] K2 SSB audio problem(an update)

[George Winship, NC5G]

After some extensive on the air testing with my Son, this is what we have
found.
One by one I eliminated pieces of equipment starting with the KPA500, then
the KAT100, followed
by removing the KPA100 from the K2, then changing power supplies, hooking
the basic K2 to the 2.5A ps 
that I power the KX3 with. This ps is about 3ft. from the K2 on the floor,
under the desk. In this configuration, the audio was clean. Even though not
connected, I turned the KPA500 on(which is about 4 inches from the right
side of the K2) and this introduced some small artifacts which would suggest
that the VCO mod would be worthwhile.

Following this, I reinstalled the KPA100. With the small PS still
connected(the K2 does not recognize the KPA100), the bad audio problems
returned. Disconnecting the small PS from the K2, and connecting the Astron
35m(which is about 2ft. from the left side of the K2) to the KPA100, but
keeping power below 10 watts to keep the KPA100 off the results were no
different. Turning the power up to turn the KPA100 on, the results were no
different. Power output through an external watt meter closely follows the
power selected.

What now?

73, George, NC5G 




George,

Ask yourself what has changed between good operation and now.
Have you re-arranged your shack?  The K2 is sensitive to devices with 
transformers positioned within 2 feet of the left side panel - the 
transformer's magnetic field modulates the K2 VFO.

As a test, move your K2 away from everything else on the desk and run a 
test.

If this proves to be your problem, you can install the optional mod kit, 
VCOSHLDKT.

73,
Don W3FPR


On 10/21/2012 10:48 PM, George Winship, NC5G wrote:
> After 11 years of operating and many unsolicited reports of great audio, I
> am
> suddenly getting not so good reports from my K2/100. Present setup is
> K2/100, KAT100, KPA500, and resonant antennas on 75 and 40 meters. Very
> rarely do SSB on any other bands. Stations seem to have trouble describing
> the problem. Reports vary from fuzziness, distortion, to clipping. I
> bypassed the tuner and amp, hooking feed line directly to K2/100 and also
> turned the power down to ten watts to shut off the KPA100 and problem
> persists. No difference between MH2 and CM500 mics. These test were done
> with stations who know my rig and my voice. This is an early K2/100. All
> mods were done years ago to K2, SSB, and KPA100. Receive audio is
> unchanged.
> Visual inspection of boards look OK.
>
> As a further check, I connected my KX3 to amp and antennas with great
> results.





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