[Boatanchors] Disc caps vs paper caps

[WA5CAB at cs.com]

Although probably not of concern with vibrator buffer capacitors (which is 
what this thread was originally about), one common capacitor parameter that 
is usually forgotten when it matters is current rating. 

In a message dated 09/27/2012 00:15:57 AM Central Daylight Time, 
1oldlens1 at ix.netcom.com writes: 
> ----- Original Message ----- 
> From: "J. Forster" <jfor at quikus.com>
> To: "Mark Foltarz" <Foltarz at rocketmail.com>
> Cc: "Boatanchors at mailman.qth.net" 
> <boatanchors at mailman.qth.net>
> Sent: Wednesday, September 26, 2012 7:29 PM
> Subject: Re: [Boatanchors] Disc caps vs paper caps
> 
> 
> Probably true, but many ceramics are piezoelectricand can 
> have a pretty
> large voltage coefficient of capacitance.
> 
> I can't think of any reason they'd not work offhand though.
> 
> -John
> 
>      The class of dielectric makes a difference.  Zero 
> temperature coefficient dielectric, marked NP0 or C0G (the 
> 0's are zeros) AKA Class 1 dielectric, have little 
> piezeoelectric effect and low voltage coefficient of 
> capacitance.  They have the lowest dielectric constant so 
> are large in comparison to other ceramic types.  Hi-K 
> ceramics are popular for surface mounting and other 
> applications where size is important but even low-K ceramics 
> are small in comparison to old style paper caps.  They have 
> the advantage of very long life and very stable operation. 
> There are some very specialized uses where they should not 
> be used but those are very few.  They will work very well 
> for replacing the vibrator caps and will probably last for 
> ever.  They are available in higher voltages than film caps.
> 
> For more see:  http://my.execpc.com/~endlr/ceramic.html
> 

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