[sdiy] VCO tracking w/o counter

[Ian Fritz]

>On 2006-05-26 20:47 -0500, Paul Schreiber wrote:
>
> > You *cannot* tune a 1V/Oct input (VCO, etc) with a scope. You
> > need a frequency counter.

I've done it without a counter, as follows:

1.  Mix a 440Hz pulse (from a xtal-oscillator timebase) with the VCO signal 
and feed it to a scope.

2.  By looking for stable beating patterns, set the VCO to various 
octaves:  110Hz, 220Hz, 440Hz, 880Hz, etc.

3. Measure the control voltage required to get the VCO to each of these 
frequencies.

4. Adjust tracking controls as usual to get 1 V/Oct.

:-)

   Ian