[Elecraft] K2 Frequency Alignment

[Don Wilhelm]

Michael,

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.

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.

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.

Since CAL FCTR is only accurate if the 4000.00 kHz oscillator is correct,
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.  Every
good engineer and technician knows the limitations of his measuring tools
and tries not to draw conclusions outside those limits.

73,
Don W3FPR

----- Original Message -----
The bottom line, I think, is that if CAL FCTR doesn't show 4000.00 KHz when
you
probe the 4 MHz oscillator that runs the MCU, the setting the 4 MHz
oscillator
exactly to 4 MHz won't work too well.  It is better to attach the probe
to some other oscillator, with a known value, and adjust C22 so that CAL
FCTR
matches the known value.