input and output impedance of a crystal notch filter

[i2ndt]

looking for a crystal notch filter, I came across this "old" topic:
https://www.edaboard.com/threads/198692/



It looks quite interesting to me and I would like to know how I can calculate or measure its input and output impedance.

TNX!

i2NDT Claudio

 

[chuckey]

The crystal is a series tuned circuit, so to maintain its Q, it should not be damped(too much!) by operating into a low impedance circuit, conversely if the impedance is too high then the notch becomes too narrow. So in the above circuit the damping R is 330 ohms.
Frank

 

[i2ndt]

tnx Frank!
so, if I want to test the circuit with my mini-VNA (whose in/out impedance is 52 Ohm) I need two 6:1 transformers to match the impedances...

Claudio