[Elecraft] KS PLL Reference Oscillator

[John Heaviside]

K2 PLL Reference Oscillator Range.

Further to my previous posting: the problem was not insensitive counter but was in some way connected with the RIT/XIT control.  The low frequency reading BAND- is now stable but is too low.  BAND+ is 12099 and BAND- 12078 giving a range of over 20kHz which is outside specification.

I have checked the circuit and all seems to be OK.
U5 pin7 (U6 pin3) is 4.06 at BAND+ and 0.01at BAND- which seems OK according to the circuit diagram.
U6 pin1 is 7.48 and 0.00.  This again seems OK as U6A has a gain of about 2 with a small -ve bias resulting from the thermistor mod.
D16 and D17 are unbiased at the low end. (They actually self bias from the RF ro a small +ve voltage at R19/C100).  This seems to be bad practice as the capacity will vary widely from component to component and result in widely varying reference oscillator range. Hence my 20kHz range?

Am I mistaken? Is there a fix for this?

John G3NYX