[sdiy] Help with Timing Capacitor types.

[Paul Schreiber]

a) Errr....a 2206 "badness" will 'swamp' pretty much all of any cap 'badness'.

b) The tempco of the cap is not the 'reason' it is picked in VCOs. It's the 
dielectric absorbtion factor. Sure, a 100ppm tempco helps and in the MOTM-300 
VCO, there is a specific tempco loop for the cap. A mylar cap is the *worse 
possible* choice. You are better of with a polyproplyene cap (Digikey sell the 
Panasonic ECQ series) rather than Mylar any day. Remember, cap technology has 
also advanced in the last 25 years. There is *no reason whatsoever* in using a 
Mylar cap (even if they are free).

Use Digikey part # P3921 at a staggering 60 cents :)

Paul S.
BTW: for the Tandy 300 baud modem filters I designed in 1980, we used about 1.7 
*million* ECQ-P caps 1% at 4700pf. Worked great!