[Elecraft] K2 PLL click educational opportunity

[Don Wilhelm]

LS,

The "PLL click" is usually caused by running CAL PLL with the bottom 
cover off.  Install the bottom cover and do it again.

The setting of C22 at exactly 4.000MHz will not usually result in the 
best dial calibration.  That 4 MHz oscillator is not used dynamically - 
it is only used during the run of CAL PLL and CAL FIL.

The best dial calibration will be obtained by following the instructions 
on my website www.w3fpr.com K2 Dial Calibration article.

In short, the procedure is to tune *exactly* to WWV (15 MHz is 
preferred) - or other AM station with a known frequency in SSB mode and 
using CAL FCTR measure the difference between the VFO (TP1) frequency 
and the BFO (TP3) frequency and setting C22 to produce exactly the 
difference equal to the station's frequency (15000.00kHz in the case of 
15 MHz WWV).
Then run CAL PLL followed by CAL FIL.
Check the results by tuning to WWV again and make slight corrections if 
necessary (do it again).

73,
Don W3FPR

On 4/3/2016 10:56 AM, lstavenhagen wrote:
> Hi all,
> Sorry if these are dumb circuit-detail questions, but my K2s (the one in use
> as well as the one on the bench being built) are sort of my self-education
> laboratories. Yesterday while out /p in the mountains, I discovered the 5khz
> PLL "click" in my #1 K2, which led to researching it in the reflector
> archives, which led to learning how PLL synthesizers work which led to the
> K2 schematic......
>
> Which led to...whew...lol... my current question about the 4.000mhz
> reference oscillator on the control board. My question is, it looks like the
> 4.000mhz osc. is the clock osc. for the main K2 CPU (U6), is that right?
>
> And, I would assume that adjusting it to exactly 4.000mhz is what yields the
> correct dial reading because that adjusts the main CPU's clock frequency?
>
> Just curious and apologies if my questions are a little dense...
>
> Tnx es 73,
> LS
> W5QD
>
>
>
> --
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