On 20 mayo, 01:44, Jack Schmidling wrote:
I am in need of zero tc caps for my VFO project
I need two at 1000 pf.
Polystirene (styroflex) capacitors are a good choice. They have a
desirable slightly negative temperature coefficient, and excellent Q.
1000pF is within the spectrum of usual values.
Or you may choose a bunch of NP0 ceramics in parallel, plus ~1/20th of
the total value made up of a N750 (-750ppm/centigrade) capacitor. Many
paralleled caps are better than a single multilayer unit because heat
(yes, real life caps do heat somewhat in oscillators) is better
dissipated away, thus reducing one of the drift causes.
73s and DXs
Daniel Perez LW1ECP