[sdiy] New VCO tuner utility circuit

[Scott Bernardi]

I got the idea for this utility circuit from somebody on the list -
whoever you are, thanks!
Basically the circuit produces a precise 1.000v step that is clocked by
an LFO. You feed the step into your VCO's CV input.  You feed the VCO
output into the tuner. You plug the tuner output into an amplifier so
you can hear it.
The VCO signal is switched alternatively between the "straight" signal
and a divide by two signal at the same time the 1v step is fed to the
CV. So whereas the 1v step would double the frequency of the VCO, the
octave divider divides it back down to the original frequency. Any
deviation is a 1 v/octave scale error, so you trim your VCO until it is
the same pitch. The ear is very sensitive to pitch differences, so this
works really good.
A CV ADJ pot lets you adjust the octave scaling at different points in
the range - good for HF Tracking adjustments.

http://home.attbi.com/~sbernardi/elec/og2/vco_tuner.html