[Amps] silver mica source

[Manfred Mornhinweg]

Alex,

I suspect that silver mica caps might not be the best option you have.

Silver mica caps consist of mica sheets with an ultra thin layer of silver 
deposited on each side. This silver layer isn't able to conduct a large current, 
so that silver mica caps are not a very good choice in transmitters. Their main 
advantage is high stability, which is important in oscillators and some other 
circuits, but not really in low pass filters. In my younger years I didn't know 
this, and had some practical experiences with them, including pretty fireworks.

You should instead be looking for mica capacitors that are NOT silvered. For 
example transmission type "metal clad mica" capacitors. These are slightly less 
stable, which is not a problem in this application, but they can handle far 
higher current.

Such capacitors are easy to make at home, if you can secure sources of mica and 
copper sheet.

At the 100 watt level, you might still get away with silver mica caps, but not 
with just any! You need to choose them for their current handling spec. There 
are ceramic capacitors that can handle the task at least as well, and probably 
these are less costly.

When you get to the legal limit level, capacitor procurement becomes a real 
problem. At that level, homemade copper/mica capacitors, or maybe copper/teflon, 
might be the best choice. Unless one is willing to pay ten, twenty, or even more 
dollars per capacitor, of course! When you need 30 capacitors for a low pass 
filter bank, it's not a trivial matter.

Manfred

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