EMRFD Message Archive 1141

Message Date From Subject
1141 2007-11-04 07:54:12 ka3j12 Effect of Crystal Load Capacitance

When building a simple Cohn type narrow CW crystal filter, does
the load capacitance specification (series or specified) really
matter? I would think it wouldn't except for shifting the center
frequency of the filter a bit. But could there be other significant
effects? In general, is it better to just go with the series type?
Thanks for your help!

73,

Ron (KA3J)

1142 2007-11-05 10:05:22 Nick Kennedy Re: Effect of Crystal Load Capacitance

It seems to me that either way, your crystal will have Lm, Cm and Rs series
parameters and Co holder capacitance and that's what you have to work with.
The manufacturer's specificaton of how much additional series or parallel C
is needed to put the crystal right on its stamped frequency wouldn't have
much relevance in your filter design.

72-Nick, WA5BDU

[Non-text portions of this message have been removed]

1141	2007-11-04 07:54:12	ka3j12	Effect of Crystal Load Capacitance
Message	Date	From	Subject
When building a simple Cohn type narrow CW crystal filter, does the load capacitance specification (series or specified) really matter? I would think it wouldn't except for shifting the center frequency of the filter a bit. But could there be other significant effects? In general, is it better to just go with the series type? Thanks for your help! 73, Ron (KA3J)
1142	2007-11-05 10:05:22	Nick Kennedy	Re: Effect of Crystal Load Capacitance
It seems to me that either way, your crystal will have Lm, Cm and Rs series parameters and Co holder capacitance and that's what you have to work with. The manufacturer's specificaton of how much additional series or parallel C is needed to put the crystal right on its stamped frequency wouldn't have much relevance in your filter design. 72-Nick, WA5BDU [Non-text portions of this message have been removed]