[ARC5] Zero Beat Question

[Robert Eleazer]

Well, thanks for the explanation.  It makes sense in that context.  Now let me explain what I was really asking.

I repaired the 1 MHZ oscillator of my URM-103/SG-297 by replacing it with a 7805 regulator feeding a 1 MHZ TTL oscillator, all built into a crystal oven case (originally the SG-297 used a crystal oscillator that employed a 1 MHZ crystal and a couple of 2N706).  That oscillator in turn feeds a harmonic generator to create calibration signals every 1 MHZ over the total range of the signal generator, 26 MHZ to 80 MHZ.  This unit is pre-digital and there is no PLL or anything to keep it locked to the reference oscillator; that is all manual in nature.

You flip the function switch to "Calibrate" and then tune the oscillator to the nearest 1 MHZ point.  You get the usual tone over the speaker when the oscillator and the marker signal beat and then use a separate control that enables you to move the red frequency stripe so that it matches what the marker says.  The manual says to Zero Beat the oscillator with the marker and line up the frequency calibration that way.  So it may at first show the marker signal is on 45.050 MHZ and you just move the calibration red stripe to match the marker, put it right on 45.00 MHZ.

But if you are Zero Beating the oscillator with the marker, then there should be no tone, right?  So how can you use the tone to set the calibration to set the oscillator calibration?  When the tone disappears you'll be on one side of it, right?

Thanks,

Wayne
WB5WSV                 
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