The issue is the dielectric on low frequency, a doorknob capacitor can stand
3 amps on 3.5MHz. but only 1 amp or less on 1.8 MHz. Because of the high
loss on 1.8 MHz the capacitor get hot, than if it is not NPO, it changes
capacitance, as a result the tuning drift away. There is no NPO doorknob or
ceramic capacitor above 170pF. The only solution is to parallel small NPO
capacitors around 60 pF, more capacitor means more current and less heat.
Regards
JCarlos
N4IS
-----Original Message-----
From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of Chris Wilson
Sent: Wednesday, December 04, 2013 4:24 AM
To: amps@contesting.com
Subject: [Amps] Why do commercial makers parallel up small value caps in pi
circuits?
04/12/2013 09:21
In many commercial high power tube amps the ceramic caps in the tune and
load circuits are small value, paralleled up to create a bigger value. Is
this because smaller values drift less? Thanks.
--
Best Regards,
Chris Wilson.
mailto: chris@chriswilson.tv
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