Carl wrote:
>
>Silver micas are still readily available in the US.
>Mouser carries a reasonable collection of 500V and ARCO still produces
>them.
>
>Amp Supply used a Teflon insulated disc cap but I never did find out the
>source; they ran up to about 12KV or so.
>Ameritron uses a pair of 1000pf 7.5KV discs in parallel and they seem to
>work just fine at 1KW out of an AL-80B, no overheating noted.
>
It seems to be a case of choosing a high DC voltage rating, and hoping
that the RF voltage and current ratings (two different things) will both
be OK. Just wear earplugs for the first six months?
>Apparently there are sources but the manufacturers seem to protect them
>from the mere mortals that would dare to build instead of buy.
>
More likely they protect their cost-cutting sources from one another.
So... let's try to gather some data points of our own. For example, at
what power levels do SEMCO silver micas start to go bang in lowpass
filters for various bands? And was it voltage or current that caused it?
73 from Ian G3SEK Editor, 'The VHF/UHF DX Book'
'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.demon.co.uk/g3sek
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