On Fri, 12 Mar 1999 08:01:33 -0500 (EST) "William L. Fuqua III"
<wlfuqu00@pop.uky.edu> writes:
>
> I did fail to point out that it could be that NPO's are
>more desireable because they are usually physically larger
>than the cheaper caps.
>73
>Bill
>> Why NPO? With Q=2 Bandwidth (-3db) of the tuned circuit
>>is F/Q = .5*F or 50%
>>10% change in capacitance would only produce 5% shift in frequency.
>> One advantage in using higher voltage capacitors is that they are
>>physically larger and can handle more RF current due to the larger
>>surface area.
>>
>>
>>73
>>Bill wa4lav
NPO disc are rarely available above 220pf or so in 500V size. The 1KV
units are most likely to be Y5P or SL
Mica caps, OTOH, have been historically used in tuned circuits where RF
heating is expected. I remember reading somewhere that the TC of micas is
opposite that of the inductors and results in a higher circuit stability.
True or false?
Disc ceramic are cheaper but does anyone know of a commercial amp that
uses them in a tuned input?
73 Carl KM1H
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