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[TenTec] Intermittent Freq Shift

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Subject: [TenTec] Intermittent Freq Shift
From: wdcook@ibm.net (wdcook@ibm.net)
Date: Tue, 22 Sep 1998 17:22:48 -0400
I have an Omni VI upgrade 3.  I have had this RX/TX chirp that has
been described here recently.
    I called TT svc and they told me how to align U13 (PLL IC)
on the logic bd with the xtal osc bd.  I used a Tek 455 50mc
scope as follows:  Chan A  2v/div
                   Trig on Chan A
                   Horiz .05 usec/div
                   use the + - slope button to position the
                   negative going pulse in from the left side
                   of the screen.
    The Chan A probe(X10) is on pin 11 of IC U13.  Adj trig for
visual stability.
    Now adjust L12 thru L21 (each on its selected band) for the
narrowest pulse on the scope.  Realize that if you use a metal
tuning tool to tweak; when you remove it the pulse width will 
change slightly. (A real pain for perfectionists).

    You must first set the ref xtal osc(20mc) on the logic bd
to 20,000,000.0 cycles after the unit has been on for a long
time to reach thermal stability.  I have access to equipment
that allows me to adjust to a tenth of a cycle.  In reality
ten cycles is probably good enough.
    Phew! enuff said for now.

Bill   N4WC

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