[Elecraft] New K3 app note issued.

[Phil Hystad]

OK, how do I find out if I need this mod?   I have witnessed two different frequency shift problems, one of them I have posted here and there has been some discussion about it.

Problem #1 (posted before) -- when listening to CW, when the signal is reasonably strong such as S9 or better, if there is a slight pause in the sending there is sometimes a frequency shift on the order of 10 Hz to 40 Hz.  I am guessing at the actual shift amount as it is a slight but very apparent shift in tone.


Problem #2:  on a couple of occasions while operating PSK, there has been a slight shift in frequency, enough that my software is no longer tracking the signal (I use CocoaModem).  I am not sure how much a shift would need to be for CocoaModem to lose sync but it does lose sync.  This has happened a few times.  At first, I thought it was the other guy hitting his VFO or maybe some old tube rig that is has an unstable VFO but the last two times it happened I am pretty sure that it was me (and, my hands are no where near the VFO knob).


By the way, as far as I know, in neither case above, does the VFO frequency readout change value.  For PSK, I keep my VFO pegged on 14070.150 Hz and I think I would notice if this changed.


73, phil, K7PEH


On May 27, 2010, at 3:54 PM, Bruce Beford wrote:

> The app note for modifying the K3SYN board has been posted to the K3
> Enhamcements and Application Notes page at:
> 
> http://www.elecraft.com/K3/k3_app_notes.htm
> 
> It is a simple one-resistor mod. Next time I have the rig open, I'll
> probably do both of mine.
> 
> Description:
> "In rare cases, at certain frequencies the DDS driving signal to the Phase
> Locked Loop (PLL) may be marginal, resulting in a sudden shift in frequency
> (commonly called "chirp"). This modification adds a resistor to the KSYN3
> board that increases the DDS drive level prevent this condition. "
> 
> "This is an optional modification and is not required unless you are
> experiencing this condition."
> 
> 73,
> Bruce N1RX
> 
> 
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