RE: [TCML] Ceramic MMC?

["Lau, Gary" <Gary.Lau@xxxxxx>]

Ceramic disk capacitors are a very poor choice for use in a tank capacitor.  In addition to being very lossy at high frequencies, they usually have a very poor temperature coefficient.  This means that as they warm up due to losses, their capacitance will change significantly, and your primary resonant frequency will change.

If you have a capacitance meter, try measuring it as you pass a match below the cap to warm it up.

But the good news is that your caps are well suited to building a Terry filter, and maybe even a Marx generator!

Regards, Gary Lau
MA, USA

-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf Of Phillip Slawinski
Sent: Friday, June 06, 2008 3:53 PM
To: Tesla Coil Mailing List
Subject: [TCML] Ceramic MMC?

A local Electronics shop near me went out of buisness recently.  They
were selling their entire stock at half off or better.  I managed to
pick up 222 10000V 1000pf Ceramic capacitors for about $50.  They're
red discs about 3/4" in diameter and 1/4" thick.  I've made a small
mmc ~ .01 uf and it seems to perform with the exception of some arcing
between the buss wires.

My question is if these ceramic capacitors are going to perform poorly
with RF.  I've established that they are pretty durable, and seem to
put up with TC abuse.  Should I build the rest of my MMC with these
caps, or am I wasting my time?

I don't know the manufacturer of these caps, but I'm fairly certain
they're ceramic.  They're quite dense for their size and it looks like
they have some sort of glaze on them.
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