Paul,
Your original post had the BFO at 4913.19 kHz and the VFO at 14913.05
when receiving 10 MHz WWV. Clearly the difference is not 10 MHz, and
that indicates that C22 was not properly adjusted.
Briefly, the procedure is:
NOTE: The K2 must be in LSB or USB mode - not CW.
1) Tune WWV precisely (ignoring the dial reading)
2) Adjust C22 until the BFO and VFO are different by the frequency of
WWV (10 MHz for 10 MHz WWV - the low order digits should match exactly.
3) Switch to 40 meters and run CAL PLL
4) CHANGE each BFO setting to force the K2 to record new DAC values in
EEPROM.
5) Check the results by tuning WWV again - the dial reading should be
correct.
You said you were following that procedure, but somewhere along the line
something has apparently gone wrong - the order of things is important
for this procedure to work properly. It works every time for me, and I
use it frequently.
Have you interchanged TP1 and TP3? - they were incorrectly labeled in
your original post. The frequency difference is observed between TP1
and TP2 - TP1 is located near T5 and TP2 is located below the KSB2 board
location (through access hole when the KSB2 is installed). TP3 is near
the front and is not used in this procedure - it is the PLL frequency
and will always be in the range of 12 MHz.
I suggest you simply try again.
73,
Don W3FPR
paul wrote:
Hi Don,
I have read your website (and 50+ posts) and done this procedure about 5
times over the last 3 days - each time with the same result (no change).
Followed a procedure that made the two frequencies (TP3 and TP2)
exactly 10MHz apart by varying C22. Ran CAL PLL (7.1 Mhz) and then ran
CAL FIL. Made small changes to each BFO frequency on all modes
(USB,LSB,CW,/CW) and Xtal selections. No change at all - WWV is still at
10.012 MHz. WWV voice is perfectly tuned in both USB and LSB.
Right now the radio works great except for this problem. Guess I will try
again when I get the new firmware.
Thanks for your help,
Paul
AD5IW
On Mon, 3 Dec 2007, Don Wilhelm wrote:
Paul,
The exact frequency of the 4 MHz (nominal) reference oscillator may be
slightly different than exactly 4 MHz.
If you have a well calibrated external frequency counter, you can adjust the 4
MHz reference (adjust C22) by measuring the frequency at TP1 with both the
internal counter and the external counter - adjust C22 until the internal
counter reads the same as the external counter.
Another method that provides even greater accuracy is the method outlined on
the Elecraft website on the Builder's Resource page -
http://www.elecraft.com/Apps/K2%20C22%20Adjust%20App%20Note.pdf.
This method requires no extra calibrated equipment, but there is a requirement
that the standard station be tuned with precision. When using WWV, I use
Spectrogram to observe the audio output tones, knowing that WWV transmits
tones of 500 and 600 Hz on alternate minutes (there are silent minutes and one
minute of 440 Hz tone as well). If the tones line up with my Spectrogram
markers at 500 and 600 Hz, I know that WWV is properly tuned within one or two
Hz.
After setting the 4 MHz reference, run CAL PLL and CAL FIL changing each BFO
and the resulting frequency should be within 20 Hz of the correct dial
reading.
For more information, please refer to my website article on K2 Dial
Calibration www.qsl.net/w3fpr
73,
Don W3FPR
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