[Elecraft] K2 dial alignment SOLVED!!

[Don Wilhelm]

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:
>   
>