[Elecraft] Re: N6KR's 4 MHz oscillator cal method for the K2

[Wayne Burdick]

Hi Steve,

Steven Gibbs wrote:

> ...it is my understanding that adjustment of
> C22 must be refined by an iterative process (chasing
> round a loop) by repeated measurement of PLL and
> measurement of BFO looking for a (say) 10000.00MHz
> difference.

Not if you use my new method, and that's the entire point. No iteration needed.
(Having written the K2 firmware, I'm pretty familiar with the disadvantages of
iterative methods, which is why I posted this new one.)

By definition, if you tune in a station at a known frequency, then adjust the
CAL FCTR-measured values of the BFO and VCO such that their difference is equal
to signal frequency, C22 is then optimally set. This method doesn't depend on
previously measured BFO values since the measurement is being made closed-loop
(i.e. it does not involve the frequencies stored in EEPROM from an earlier
calibration pass). You do have to re-run CAL PLL and tweak the BFOs using CAL
FIL once the change to C22's setting has been made. This is true of any method.

Your objection regarding accuracy of tuning of the reference signal can be
addressed in other ways, as noted by other posters. But from the standpoint of
adjusting C22, this is the only non-iterative adjustment method.

+/- 30 Hz at 10 meters is easily achieveable. Of course having the recent BFO
and PLL reference upgrades installed is recommended. The two together provide
excellent stability. (S/N 3000 and up have the BFO mod, and S/N 3446 and up have
the PLL upgrade.)

73,
Wayne