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3733 frequency adj.



I got a lot of replies on setting the frequency of the 3733 . here is a
procedure you can use that requires
no special equipment.

This adjustment applies to unmodified 3733's if you changed the crystal
you have to use 8.8125 instead of 8.898438

here is what you will need to do the adjustment.

a receiver capable of receiving WWVB (10mhz) and the 8.898438 oscillator
with 1 hz resolution, 10 is ok.
6 ft of coax with a connector on one end and the other end with the
shield stripped back 4 inches to act
as a pickup (probe). leave the center conductor insulated.
a computer (which you have if your reading this)
spectrogram or other DSP software capable of reading 1hz resolution.

FOLLOW THESE STEPS CAREFULLY

1. get your 3733 on the bench and turn it on. turn on your rig to and
let them both warm up for 30 minutes.
2. open the 3733 so you can adjust the xtal trim cap.
3. Tune the rig to WWVB at 10 mhz. observe the carrier on your dsp
display, tune wwvb till the carrier tone
    on the dsp display is 1000 hz.  when it is right on,  record the
display frequency on your rig..
    (ie.  10.000135) . write this down. the error is 10.000.000  +/-
your readout.  in the example its +135hz.
4  remove your antenna coax from the rig and replace it with the cable
with the stripped end.
5. place the stripped end of the cable near the xtal and tune the rig
for 8.898438 +/- the error . in this
    example the error was +135 so we would tune the rig for 8.898573.
when you are close you can watch
   the DSP display (spectrogram) and adjust the xtal till the carrier is
at 1000 hz again.
6. Place the cover on the 3733 and note the change in frequency.
readjust the xtal trimmer till when you
    place the cover on and put in a few screws that it sits at 1000 hz
again.
7. when its right at 1000hz with a few screws in  replace all the screws
and check it again.
    if its ok you are done.



using this technique I can find the beacon of ao40 and be within 300 hz.

good luck.  see you on ao40.

keith




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