Paul,
The A to B instructions do state that the PLL reference high frequency
is 'typically 12097 to 12100 kHz'.
Yours was clearly not in the typical range, and indicated that something
was awry.
You are correct that there should be a statement that the upper
frequency must be above 12096 kHz.
Incidently, a 12 uHy choke should provide a greater range than a 10
uHy. I am wondering if the 12 uHy choke you received was really a 12
uHy. I am certain it was marked as a 12 uHy - any chance that you can
measure it to see if my speculation is correct?
73,
Don W3FPR
paul wrote:
Last year, I upgraded my K2 from rev A to Rev B. Afterwards the dial was
off by 12 KHz at 10MHz, even after setting the 4Mhz crystal, doing CAL
PLL, CAL FIL more than 30 times. Yes, I followed every procedure posted
and verified the 4 MHz clock accurately. Prior to the upgrade, the dial
was right on.
It turns out that the VCO max frequency must be at least 12096 khz or the
dial calibration will be off. This should be in the FAQ, along with how
to fix it in the upgrade instructions.
After making the rev A to B mod, the VCO range was 12084.87 to 19094.44
creating the 12Khz dial error - no matter how many alignments attempted.
Finally I just tried experimenting with the VCO. I put in another
crystal in parallel with X1 (that came with the BFO upgrade) in X2.
The VCO range was 12081.52 to 12098.17 which fixed the dial error, but
the VCO was too wide at 17.19 Khz.
I swapped out the 12uH inductor (L31) with the old 10uH inductor and got a
VCO range of 12084.87 to 12094.44 - dial calibration was way off (Yes, CAL
PLL and CAL FIL were run after each of these changes).
Then I removed the second crystal at X2 that I had temporarly installed
two steps above. VCO range now 12090.70 to 12097.63 - BINGO - the
dial is dead on!!! The VCO is a little narrow at 6.93 Khz, but I have no
plans to use 160 meters - so this should be ok.
So the solution was to go back to the 10uH inductor.
I have spent several weekends and nights trying to figure out this
problem. While I have learned a lot doing this, please put this in a FAQ
somewhere and save someone else the trouble.
Paul
AD5IW
On Sun, 2 Dec 2007, paul wrote:
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