[Elecraft] 4Mhz Calibration.

[Ferguson, Kevin]

>If you are using a frequency counter, just because it says you are at
>4.00000000 MHz doesn't mean you are!  When was the last time you calibrated
>its timebase? 

2 things: 

1)Don't measure the 4 Mhz directly, as the counter will load the oscillator,

and the frequency will change when you disconnect it.  The correct methode
is
to match the internal counter reading and an external counter while BOTH are
connected to the VFO. See manual for details.  The correct reading will NOT
be
4 Mhz.

2)I know my counter is calibrated because when I made the adjustment, I 
tuned the K2 to WWV's 10 MHz carrier, and beat the counter's 10 MHz timebase

against that, and tweaked the trimmer in the counter to better than a 1 Hz 
match. 

When you get this close, you can see the beats on 
the S-meter.  I find that propigation modulates WWV at a 1/5 to 1/10 Hz
rate, 
so it is hard to zero beat any better than that...Still, if you get the
beats
down to 1 Hz, then your timebase accuracy is 1/10 ppm! With the narrow CS
filter, 
it is easy to tune the K2 so you only hear carrier....one error I have made
with less
selective rigs is to zero beat to one of the audio tones that are
transmitted
between ticks instead of the carrier.  

Using a counter, the 4 Mhz adjustment can be done while recieving any
frequency, 
so you can listen to your counter time base drift up and down, and nail the 
adjustment just when the timebase drifts into perfect zero beat.

Seemed to me that there was something really elegant and crafty about using 
the radio to calibrate the counter that was being used to calibrate the
radio.