[ICOM] 756Pro Alinement

[Larry Benko]

The 756Prro alignment is actually very easy to do.  The service manual 
explains it all but basically the entire frequency chain is controlled 
by the 64.000MHz oscillator (X52, CR-338).  Coarse adjustment is done by 
adjusting L52 (must open radio up) and the fine adjustment is done by 
R32 (accessable via the right side of the radio).  The DSP controls the 
USB/LSB offsets etc. and once the master oscillator is set there is 
nothing more to do.  I am assuming you only need to do a fine adjustment 
(R32).

Before doing any adjustment make sure the RIT is OFF and the PBT is set 
to default.  In my opinion the easiest and possibly the best way to do 
the alignment is to tune the radio to the highest WWV frequency 
broadcast you can hear well (5, 10, 15,20,25MHz).  Now download Digipan 
ver 1.7 (I think that is current) and load it on you PC. Make sure the 
option to show frequencies is on.  Take the audio output of the radio 
and put it into your soundcard.  Adjust the volumes so the Digipan 
"waterfall" display is not too dark and not washed out.  Set the 756Pro 
to exactly the frequency you are expecting WWv to be even if  1KHz 
higher sounds bettter.  Now switch the 756Pro back and forth from USB to 
LSB.  WWV transmits a 500 Hz tone or 600 Hz tone during most of the 
time.  These tones appear as continuous lines in the Digipan display.  
Click you mouse on the line and Digipan measures the frequency to 
0.1Hz.  What you are trying to do is to get the tones to be exactly the 
same frequency for both USB and LSB reception.

While this may sound hard, if you do any PSK31 operation it is only a 
few minute test.  I have been able to set my 756PRO and 746PRO (with the 
CR-338 osc.) to within 1Hz of perfect easily.  By the way make sure the 
rig has been on for a while before tweaking R32.

73,
Larry, W0QE