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Re: 12MHz xtals and QER Filter

Rahul Srivastava
 

Very true Allison,

Xtal prams will differ from manufacturer to manufacturer hence it is of out most importance that we characterise the xtals that we are going to use.

Here in India I assume that the xtals available in mkt are same with Farhan as well as with me. 12 MHz HC-49S xtals that I measured came around 17.xx Lm. I guess Farhan also had the values in similar range. Surprisingly 11.0592 MHz xtals were way too high with Lm of around 25 hence not an easy drop in for uBitx, I tested these as wanted to move away from nice looking round numbers? every where ie mainly IF and? products from 16MHz in Nano board. Wes Hayward in one of his papers gives a detailed description of difference between HC49U and HC49S xtals in terms of motional inductance. People doing scratch build should be careful about choice of xtals.

ATC caps may not be easy to come by hence parallel caps warraants further investigation. Effect of Q was more pronounced on U type xtals.

Interesting to note your? observations on BLN cores, another point to look into.

Fun we had in school during Physics lab sessions is back...!!?

73

Rahul VU3WJM
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