[sdiy] Cheap frequency counter for oscillator calibration

[David G. Dixon]

> But in regard of the workflow of setting the octave width a tune fork
> has the same problem as the frequency counter. David Brown described it
> very well as "you're just chasing your tail as both frequencies shift".
> While setting the ocatve spread you have to concentrate on the relative
> tuning in the (multi-)octave jump. This can be controlled very good by a
> trained ear.

There's always one frequency on any oscillator which does not shift
regardless of the settings of the tuning trimmers; namely, the frequency at
CV = 0V, or the reference frequency.  If octave tuning is done off of that
frequency, then tuning is much easier, is it not?