[Elecraft] XV-222 Oscillation during TX

[Myron Cherry]

Mike, I've had the very same problems with both my 222 and 432 transverters just as you.  With the top of the enclosure in place, it goes into oscillation.  With the top removed, problem solved.  I don't have the problem with my 144 transverter.  Also, I have found that I can't stack anything metallic on top of either the 222 or 432 transverters with the top of the enclosure removed or oscillation becomes a problem again.  I have replaced both top covers with plexiglass purchased from Lowes.  Easy to cut on the bandsaw.  All problems are now solved and it also looks cool. :-) 73....Myron....K4YA 
 > From: k9mk at flash.net
> To: elecraft at mailman.qth.net
> Date: Sat, 20 Aug 2011 13:29:16 -0500
> Subject: [Elecraft] XV-222 Oscillation during TX
> 
>    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.
> 
> 
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