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Electronics => Beginners => Topic started by: Dave Turner on December 27, 2013, 11:21:08 pm

Title: Testing crystals
Post by: Dave Turner on December 27, 2013, 11:21:08 pm
A simple question for many I've no doubt.

How do you determine whether an unknown crystal say supposedly 8MHz is viable or not when you don't have an existing proven oscillator to test it as a replacement?

Is the test rig of, say a Pierce oscillator, not working because of the crystal or poor layout or any other reason?

More importantly, using a basic signal generator and oscilloscope one can easily obtain, at least, a rough estimate of capacitance & inductance. Is the same possible for a crystal?

Compliments of the season to all.
Title: Re: Testing crystals
Post by: Rory on December 28, 2013, 12:54:39 am
When it comes to crystals, there is really no such thing as a simple answer.  If you're looking for a go/no-go tester whcih spits out the frequency, do web search for "crystal tester". Lots of schematics out there. If you want to find out the particular crystal's device parameters, you need to find out how it's done. One name comes immediately to mind: Wes Hayward, W7ZOI. Look up his stuff. Much of what is published today is derived from his work.

Let me point you to a link to get you started... though it is focused on using discrete crystals in bandpass filters, the fundamentals are there.

http://pages.suddenlink.net/wa5bdu/crystal_slide_show.pdf (http://pages.suddenlink.net/wa5bdu/crystal_slide_show.pdf)
Title: Re: Testing crystals
Post by: vk3yedotcom on December 28, 2013, 04:17:36 am
Wes Hayward's stuff is good.

Or knock up an oscillator like this which works with almost all HF crystals.

Building electronics from schematic diagrams (https://www.youtube.com/watch?v=yEnqAQbQTcE#)

An RF probe or receiver can be used to verify output.
Title: Re: Testing crystals
Post by: Dave Turner on December 28, 2013, 10:16:02 am
Exactly what I'd been looking for.
Thank You