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Re: [Amps] Mica cap substitute \ alternative

To: Ian White GM3SEK <gm3sek@ifwtech.co.uk>, amps@contesting.com
Subject: Re: [Amps] Mica cap substitute \ alternative
From: Peter Chadwick <g3rzp@g3rzp.wanadoo.co.uk>
Reply-to: g3rzp@g3rzp.wanadoo.co.uk
Date: Fri, 14 Jul 2006 11:03:04 +0200 (CEST)
List-post: <mailto:amps@contesting.com>
Ian said:
> the derating above 5MHz may not be due to the 
mica at all. It could well be due to heating in the very thin 
metallization, which would  increase with frequency due to the skin 
effect.<
Wouldn't one get the same effect with ceramic caps, where the electrodes are 
similarly formed?
The old WW2 micas that Rich talks about were. I believe, mainly the 'stacked 
foil and mica' type, where the electrodes were relatively thick and so had  
relatively high thermal capacity and heatsinking ability. So we can accept that 
they did get derated at frequency, but we don't have an answer as to why.
73
Peter G3RZP
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