VCO hacks, tweaks

[Grant Richter]

A couple of odd notes:

1. Main timing cap

During the summer we had a problem with an ultrasonic oscillator for a
customers product.
The units wouldn't calibrate with the fan blowing on it. The original
design used 1% (ouch) polycarbonate
caps for tuning and 1% 50 ppm metal film resistors.

The polycarbonates are listed at +150 ppm +/- 50 ppm per Deg. C

I replaced them with KEMET ceramic COG caps and the problem went away.

COG caps are rated 0 ppm +/- 30 ppm per Deg. C

Something to think about....