[Elecraft] XV-222 Oscillation during TX

[Mike & Becca Krzystyniak]

   Last night I was talking with a local on 222 SSB, and I noticed most of
the lights on my XV-222 bar graph were staying on in TX, like it was in a
peak-hold mode.  At the same time I noticed Hi-RFI alarm coming up on the K3
display while transmitting.  A quick check and everything seemed tight, SWR
was good, and no other rigs were on (at least in TX).  I did look at some of
the reported RFI cases here on the reflector, but they seemed to be RFI into
the XV-222 from other rigs.

   So, I popped it on my spectrum analyzer and, while transmitting, there it
was, a strong osciilation at about 300 MHz.  Now, with 222 present it swamps
the oscillation so when you're sending CW, the oscillation is present
between the character spaces, and on the watt meter all you see is around
15-20 watts output. Or like FSK with a 78 MHz shift.

   Next I popped off the XV-22 top cover and of course the problem was gone.
I suspected that there was coupling from the PA output into the top cover
and back into an earlier stage causing this instability.  In fact, I can
hold the cover in my hands, and covering just half of the XVTR PA and it
starts oscillating.  Has anyone seen their XV-222 unit oscillate during TX
(sans an applied 222 signal)?  

   Oh, yea, everything has been sanded and grounded per the instructions and
as suggested by Wayne in the RFI emails.

   Has anyone seen this on their unit?  Is there a tech note or app note out
there on this?     

   Thanks in advance. 

73  Mike K9MK/5   Haslet TX.