Hi Bottom line - if you are designing a filter, you need the real values for the Cm, Lm and C0. Guessing at them is likely to lead to trouble if it is a reasonably complex filter.
Rm generally goes as the overtone. It can deviate quite a bit from that (as can the other parameters) depending on how the blank is shaped and plated. ( If I want a good 3rd overtone, it will be designed to work well there. It may be pretty bad on the fundamental ….). Bob > On Sep 18, 2019, at 2:35 PM, Glen English VK1XX > <glenl...@pacificmedia.com.au> wrote: > > I wonder if anyone can shed any light on this question, since this forum is > loaded with those who REALLY understand crystals. > > I am modeling crystal filters (VHF) in SPICE. There are some specific > acoustic mode models for SPICE in some Post Doctorial papers, very > interesting, they would be the best but rather painful to use. > > However I using simplified Rm, Lm, Cm, Cs, Cp, Ccase etc > > My question is, how does Rm vary with overtone number ? > > My assumptions are Lm stays the same, Cm reduces proportionally to the square > of the overtone number. Those assumptions are close enough and canon. > > I of course need the Rm number to acurately model loss. > > 73 > > glen english > > VK1XX > > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
