[ICOM] IC-751 MO Calibration

[Adam Farson]

Hi Mike,

There is a 2-step calibration process for the master oscillator; firstly,
you can zero-beat the calibration marker with WWV (offset 1 kHz in USB or
LSB mode to produce a 1 kHz tone). If the CAL pot under the door on top of
the radio is out of range, there is a calibration procedure in the service
manual. The idea is to set the CAL pot for 3V at the test point, as I
recall, then adjust the master-oscillator coil using either the counter or
WWV as a reference.

The carrier-insertion oscillator (BFO) may also be off. You can check that
by tuning in an AM signal and switching to USB, then LSB. The audio pitch
for both USB and LSB should be the same as on AM. There is a BFO alignment
procedure in the service manual; you will need to use your counter.

I have an IC-751A service manual, and have done the MO calibration on a 751A
I once owned.

Cheers for now, 73,
Adam VA7OJ/AB4OJ


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