[Milsurplus] replacement question -

[Bob Camp]

Hi

Performance is mainly dependent on the dielectric, so unless mica has changed over the years, it should be about the same as today. Nominally they have a positive tempco in the 50 to 100 ppm / C range. Reasonably high Q and good stability with voltage are the norm for mica. A modern NPO ceramic formulation should do as well / better than a similar value mica. Back in WWII ceramics were not as well developed as they are today. The equivalent part (value wise) was a big bigger and thus had a lower SRF / worse Q. The early(er) ceramics also had some issues with moisture that mica in general does not have. 

Bob

On Aug 10, 2013, at 1:11 PM, John Hutchins <jphutch60bj at gmail.com> wrote:

> Question - Silver Mica capacitor replacement .
> 
> "Normally" the Silver Micas never need replacement but if they have to be replaced is could that be effectively replaced with a modern ceramic with the appropriate
> tolerance and temperature characteristics.  which leads me to this question:  In WW2 what were the typical characteristics of a Silver Mica capacitor?
> 
> Just shoot me for asking.
> Hutch
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