[Elecraft] K2: Problems With PSK

[Don Wilhelm]

  Jon,

Yes, I sleep - you will only rarely see a post from me between midnight 
and 8AM local time.  I do check my email periodically throughout the day 
when I am home, and that is most of the time.

Back to your LSB/USB problem.  There should be little difference between 
LSB and USB provided the OP1 filter is somewhat symmetrical and is 
relatively flat within the passband.  You should be able to see that 
with Spectrogram.  Did the LSB and USB passband shape look about the 
same?  If not, then the filter is to blame.  Check the capacitors to be 
certain all are the correct value (CA thru CP).  If the capacitors are 
OK, then first check the soldering in the filter area (re-flow it with a 
hot iron, adding a tiny bit of new solder and flux).  If the passband 
for LSB and USB are still not close to the same shape, you will have to 
change to a new matched crystal set (7 crystals).

Check the carrier balance in both LSB and USB.  If you have a 'scope, 
you can connect it across the dummy load, and using a sensitive 
amplitude setting on the 'scope, plug paddles into the key jack (do not 
connect a mic), close the dot paddle and adjust the carrier balance pot 
for minimum RF - check both LSB and USB to be certain they are both the 
same.
You can use the S-meter of another receiver to make the same check, but 
the 'scope is easiest.

If the passband shape for USB and LSB are the same, you should have good 
output no matter which sideband is in use.

One temporary "solution" - BPSK does not care which sideband you use 
(while others do care), so you can use the one that works well.  That 
does not fix it, but allows you a bit more operating time.

73,
Don W3FPR

On 10/10/2010 10:22 PM, Jon Perelstein wrote:
> Don,
>
> Do you ever sleep?  It seems as if every time I post something, no matter what
> day, no matter what hour, there's a response from you within a few minutes. hihi
>
> Seriously, thanks for your reply.
>
> You had me set the RTTY FL1 BFO about a week ago using Spectrogram.
>
> At any rate, the problem I'm having happens when doing PSK with mode USB as well
> with mode RTTY (reverse).
>
> Jon
> KB1QBZ
>