[Elecraft] 4 MHz alignment

[k6se@juno.com]

kevinrock@earthlink.net wrote:

"Since I do not have a frequency counter I am attempting to adjust C22
using my Icom 706 and zero beating.  The zero beat area is quite broad so
I am wondering if this method is as accurate as the third technique of
using Spectrum whilw receiving WWV.  I have a test lead from the SO 239
on the Icom laid  across the XTL on the control board.  I am adjusting
C22 with a metal screw driver and achieving a zero beat as if I was
tuning a guitar.  The frequency probe is plugged into P6 and TP3.  The
CAL FCTR menu choice is set.  But it appears much less sensitive than
while tuning against WWV using the technique in the assembly manual or
the technique of using Spectrum.  Is there something wrong with my
technique or should I just find a frequency counter somewhere and use it
to allay my doubts?"
==========
If your Icom 706 is accurate on 5 MHz WWV (or 10 MHz WWV), then using
your 706 receiver on 4000.00 kHz will be more accurate for setting the 4
MHz oscillator than by using Spectrogram and WWV.

To check your 706's accuracy, tune WWV in while the 706 is in the SSB
mode.  During the first 30 seconds after most time announcements, WWV
transmits a constant audio tone.  During this tone, switch the 706
between USB and LSB and tune the signal so that you hear no pitch change
in the tone on either sideband.  Doing that, you have exactly zero-beat
WWV, and you can look at the frequency readout on your 706 to see how
close it is.  If the dial is not precisely accurate, there might be an
adjustment in your 706 to set its oscillator more accurately.  This info
might be in the 706 manual.

Anyway, if your 706's frequency readout is accurate on WWV, you can use
the 706 as you have been doing to listen to the K2's 4 MHz oscillator. 
It's not necessary to have the K2's freq probe in TP3 (in fact, it's
advisable not to because the probe in TP3 pulls the PLL reference
oscillator slightly) nor is it necessary to have the K2 in the CAL FCTR
mode.

Set your 706 to 4000.00 kHz in either USB or LSB mode and adjust C22 on
the K2's control board so that the K2's 4 MHz oscillator is zero beat in
your 706 as closely as you can determine.  Switching between USB and LSB
on the 706 might help determining zero beat, but there's no audio tone on
the K2's 4 MHz oscillator, so zero-beat cannot be determined as
accurately as it can be with WWV.

Now, after you have the K2's 4 MHZ oscillator zeroed on 4000.00 kHz as
closely as your ear can determine, switch your 706 to the CW mode. 
Adjust the VFO on the 706 so than the K2's 4 MHZ oscillator is heard at
the same pitch that you have your 706 set up for on CW.  The frequency
readout on your 706 shoulld read exactly 4000.00 kHz if you have the K2's
4 MHz oscillator set correctly, even though the signal is not "zero-beat"
in your 706 on the CW mode, i.e., you'll hear a 600 Hz or 800 Hz tone,
i.e., equal to the offset frequency your 706 CW pitch is set to.  You
also should be able to switch between CW-USB and CW-LSB on your 706 and
the pitch of the received signal (the 4 MHz oscillator) should not
change, nor should the 706's frequency readout change (assuming the 706
is like most modern receivers).

Be sure to do a CAL PLL after adjusting C22.

Compared to using an external frequency counter, the foregoing method can
easily be more accurate if the frequency counter has not been recently
calibrated.  This all may sound complicated, but the procedure is quite
easy to do and is quite accurate.

73, de Earl, K6SE