I would think that just putting resistors in series with each side of the crystal would raise the impedance enough to unload the Q. I would start with 1 K ohm on each side (for the series measurement), and see if it narrows the response. Of course this comes at the expense of increasing the attenuation of the DUT.
Stuart K6YAZ
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-----Original Message-----
From: alan victor <avictor73@...>
To: nanovna-users <
[email protected]>
Sent: Wed, Jul 10, 2019 5:02 pm
Subject: Re: [nanovna-users] Narrow band filters and LO phase noise/jitter?
A thought experiment and an issue with comparison of the single crystal with the matched filter counterpart. A single crystal in series mode is embedded in a 50 ohm system, in this measurement. Essentially, operating with a doubly loaded Q. If this de-Q effect is significant, the issue we are trying to address may not show itself. We really would like to transform the VNA source and load in affect to an impedance level that would operate the xtal as close as possible to its unloaded Q value. Of course, NOT a straight forward task.
