[Elecraft] K2 Frequency Alignment

[Masleid, Michael A.]

Hello Don,

I think this is a bit more complicated.

>You have hit the nail on the head.
>Attaching anything to the 4 MHz oscillator circuit will pull its
>frequency!!!
>My rule of thumb - never attempt ot measure the frequency of an =
oscillator
>by connecting to the oscillator section - measure after a stage of
>buffering, or use indirect pickup methods.

There is an exception.  When you measure the frequency of the reference
oscillator of a counter with the counter itself, it should show the same
value, regardless of what frequency it is actually running at.  A one =
foot
ruler is exactly one foot long, if you use that same ruler to measure =
itself.

>Sooooo - when one attaches a probe, adjusts it to exactly 4000.00 kHz, =
then
>removes the probe, the oscillating frequency is NOT 4000.00 kHz =
anymore.

Understood.  To compare the 4 MHz oscillator to other signals, I hang a =
wire
clip near the top of the crystal.  To make sure I'm not messing up the
oscillator, I watch the signal get lost in the noise as I pull the clip
away from the control board.

>Bottom line - don't do it that way!!!  Apologies to the experienced =
folks
>who already know that, but I fear there are several looking and =
listening
>who are not aware of the consequences.

This method is per step 3, page 45 of the Owners Manual, revision E.  =
Not
useful for setting C22, but certainly a good way to test the counter.  =
In
my case, in step 3, I get 3999.98 kHz.  It doesn't change when C22 is
adjusted.

>Since CAL FCTR is only accurate if the 4000.00 kHz oscillator is =
correct,

Are you very sure of that?  For some reason, on #3430, CAL FCTR gives =
results
that are 5 parts per million low when the oscillator is set to 4 MHz.  =
Is
it possible that the correct value for the 4000.00 kHz oscillator is =
about
4000.02 kHz in my case?

>using CAL FCTR to measure a known external frequency (such as a stable
>oscillator) and adjusting C22 until the display shows the correct =
frequency
>of that external oscillator is an excellent method.
>Just be certain that you do know the frequency of that external =
oscillator.
>The finished product is only as good as the tools used to produce it.

I agree fully.  Another method involves measuring an unknown oscillator =
that
is at least stable.  Calibrate the K2, and check error against WWV and =
other
known standards.  Use the error to extimate exactly what the unknown =
must have
been, and adjust C22 to display that frequency for the unknown =
oscillator.
Calibrate the K2, and check error against WWV again, repeat as needed.

73, Michael, AB9GV