New K3 app note issued.

[Bruce Beford-2]

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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[Bruce Beford-2]

That should read "Enhancements" not EnHAMcements", of course. 8-)
Bruce N1RX
K3 #559


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[Phil Hystad-3]

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
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

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[Don Cunningham]

Phil,
The ap note itself says it applies to rigs before approximately 3922 serial
number.  I looked to see if my 4076 was covered, although I have not
experienced the problem yet.
73,
Don, WB5HAK

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[Bill W4ZV]

Phil Hystad-3 wrote

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.

Neither problem.  This mod applies to a chirp in your transmitted signal, usually when operating split.  It does not apply to received signals.  

73,  Bill