Rick Karlquist wrote:
> Mark Robinson wrote:
>> So maybe a polyester film capacitor? I imagine that the current is major
>> issue in the selection of the capacitor here
>> Mark N1UK
> The only low loss RF plastic dielectrics are teflon, polyethylene,
> and polystrene. Capacitors made from polyester/mylar, polypropylene,
> or polycarbonate with have something like 2% dissipation factor. IOW,
> the Q will be only about 50. Also, they may have substantial inductance,
> being rolled up. Not recommended.
I agree with polycarbonate and polyester being high dissipation factor,
but PP is quite low (typically <0.05%), hence the use in switching power
supplies, etc. In that application, they couldn't tolerate a 2%
dissipation factor. The problem will likely be getting low enough
capacitance in a PP cap though..
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