[Elecraft] K2 Freq-Calibrate

[Masleid, Michael A.]

I was wondering how accurately I could calibrate the K2 using the
method proposed by Steve Gibbs GU3MBS last December.  I set up
an OCXO controlled PLL to generate 4 MHz, verified that it was
within 0.02 ppm of WWVB, and used that to trigger a scope.  I put
a probe near C22 and turned up the gain enough to see the 4 MHz =
oscillator,
then adjusted C22 so that drift was less than a fraction of a cycle per
second.  It takes patience, but it sets up the 4 MHz oscillator within
0.1 ppm.  I then ran CAL PLL and CAL FIL and checked calibration on
several bands by zero beating with SPOT.

Calibration is off by about 3 ppm, for instance, WWV at 10 MHz comes in
at 9999.97 KHz.  What is happening?

I did this with #3430, with the PLL temperature fix.  At page 45 in the =
manual,
the test of the frequency counter, I got 3999.98 KHz.  This means that =
the counter
is 5 ppm low, give or take 2.5 ppm.  That doesn't change with C22, since =
the
4 MHz oscillator is the reference for the counter.  This counter being =
off will
cause CAL PLL and CAL FIL to set everything at too high a frequency, so
stations will seem to be somewhere between 2.5 and 7.5 ppm low - in my
case, 3 ppm.

If I set C22 so that the counter is on the money, the 4 MHz oscillator =
will be off
a bit.  This will throw the internal "birdies" off frequency a little, =
but that's OK.  Is
this normal?

I'm sure I can set C22 by the book - but using a reference oscillator =
and scope
looked like it would be fun to try.

Michael AB9GV