[R-390] Paper Capacitor Replacement II

[Barry]

> For a capacitance bridge, you would really like a polystyrene 
> cap.  Polypropylene may be the next-best of the common dielectrics, 
> but still not as good.  It would be unwise to add silver micas to 
> make up the value, due to their inferior dissipation factor and 
> dielectric absorption -- better to leave the cap below value and 
> apply a correction factor to your measurements.  You will want to 
> know the value of the capacitor you install to better than 1%, so you 
> will need to measure it with a calibrated meter or bridge before you 
> install it in any event.
> 
> Best regards,
> 
> Charles

So, an all-polystyrene "array" would be best?  I found some 0.047uF @ 1000V.  Ten of those in parallel and then some smaller value polystyrenes to get it to 0.5uF within as close as I want to get it.

The idea of applying a constant correction factor isn't very appealing and getting this new capacitor to under 0.05% or better should not be too hard to do (as long as the met lab doesn't turn me away).

Any problem/caveats with this approach?

Thanks again,
Barry - N4BUQ