JH's VCO

[Martin Czech]

:::I have been just playing with the thyristor-based VCO Juergen posted
:::some time ago (well, just the core Q1-Q8, J1,J2 and U3, I don't need

The SCR trigger point should be quite stable over temperature (matching),
however the leakage currents are not. But this would of course
mostly influence the low end.

I should add that if you use a triangle vco as hf vco in this way the
waveform doesn't matter. It's simply a clock.  Then you can improove
hf tracking by simply changing the integration cap into a RC series
circuit. The R should be a trim pot, of course.  This gives sharper
frequency at the high end, of course with nonideal tri waveform.

All osc circuits that need good linearity use a triangle osc, if it has to
be saw they use up to four parallel osc in order to hide the discharge
time of the individual.

m.c.