[Hammarlund] Paper caps

[Gottfried Ira]

James A. (Andy) Moorer wrote:
 > Ceramics for the RF deck for bypass.
 > If you have to replace a mica, use a modern dipped mica for stability.
 >
 > You shouldn't use the Orange Drops anywhere the frequency is over 1 MHz
 > or so. They have more inductance than, say, the ceramics. I measured the
 > self-resonance of a .01 uF Orange Drop as 1.5 MHz, which means it is not
 > acting like a capacitor any more at that frequency and above.
 >

For the purpose of bypassing RF to ground, only low impedance is important,
it does not matter if this impedance is capacitive or inductive.
This also applies to coupling capacitors - in most cases (depends on the circuit).
Usual disc ceramics are lossy (OK for bypassing) but show excessive
degradation at elevated temperatures (e.g. -80% of the rated capacitance !)

Ages ago I did some measurements... the results can still be found here:
http://www.oe1ira.at/hc/hammarcapac.html

Gottfried Ira

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