[Elecraft] K2/100 VFO cal problem - need help

[Ron D'Eau Claire]

Tim, the trick, as Wayne points out, is to set the 4 MHz clock "dead on"
4.0000 MHz. Then run Cal PLL and Cal FIL to make the K2 re-calculate all
the VXO control signals and your K2 will be as close as the firmware
will allow it to be. Be sure to change each BFO frequency as you run
through CAL FIL again to force the K2 to re-calculate the control
voltages needed. 

I find that my K2 is normally with 20 or 30 Hz on the frequencies that
I've checked. Keep in mind, if you are checking with a buddy on the air,
that a lot of $5,000 equipment is further off than that. Also, the K2 is
NOT capable of holding that sort of accuracy in normal operation -
especially if you have the KPA100 amplifier installed. 

The only standard I believe is WWV (or CHU).  The SW Broadcasters are
usually VERY close to their 5 kHz intervals but I still take a frequency
reading off of them with a huge "grain of salt". 

IF you are CERTAIN your 756 is "dead on" you can use it to zero beat
your 4. MHz K2 clock with. If you frequency is off when you are done,
then I would bet that the 756 is not as accurate as you think it is, Hi!


I aligned my K2 very easily listening to WWV on 20 MHz with an auxiliary
receiver. I arranged an extra antenna pickup wire to the auxiliary
receiver that I could place near the xtal in the K2 to make a strong
beat with WWV from the 5th harmonic of the 4 MHz clock signal, then
carefully adjusted the 4 MHz clock frequency for zero beat. Actually, I
could only get within 4 or 5 Hz, but that means that the 4 MHz clock is
less than ONE HERTZ off frequency (since I'm listening to the 5th
harmonic of the 4 MHz clock, the error I hear at 20 MHz is 5 times
greater than the actual error). I guarantee that small changes in room
temperature will move the 4 MHz clock around more than that. 

If you use WWV, be sure that you are zero beating with the carrier and
not the tone signal. It can be hard to tell. If you get the 4 MHz clock
down to a slow beat, wait for the minute break in the tone. If the beat
to your 4 MHz clock disappears when the tone stops, you had it set zero
beat with the tone sideband, not the carrier. If you can still hear the
beat with the tone off, you are lined up with the carrier just right. 

The problem with WWV at 20 MHz is that they run a relatively low power
transmitter on that frequency, so you might have to fiddle around to
find a time of day when the signal is loud and clear at your QTH. I find
afternoons work well here in Oregon.

Ron AC7AC
K2 # 1289