Zero TC Caps

[K9ACT]

I am in need of zero tc caps for my VFO project but can't seem to find any info on them.  Who makes them?  What are they called?

Digikey has some with tc's of 200 ppm but that's not zero.

The also have some that are 0 +/- 500 ppm and that makes no sense.

I need two at 1000 pf.

Any light on the subject would be appreciated.

Jack

[KB2WIG]

J,
Is there any reason why you cant use NPO type caps in the circuit? Or set up a test jig and try different values of caps to find ones that don't drift as much. Another approach is to parallel up several caps to lower the amount of current through the frequency determining component - less current, less  d T and therefore less drift.   KLC

[wavebourn]

They are called NP0 (Negative/Positive Zero) Another trick is to combine one with negative tempco with another with positive tempco to get resulting zero.

[Bacon, WA3WDR]

NP0 (N P zero) is also known as C0G (C zero G).