3th overtone for crystal (21MHz-->64MHz)

[itayd100]

Hello,

I want to work with my crystal in 3rd overtone (64MHz).

I made the attached circuit and I can get just 21Mhz.
How can I get it working?


Thanks,
Itay


https://www.farnell.com/datasheets/1364712.pdf

 

[andre_luis]

Strictly speaking, there is no circuit shown at that datasheet.

 

[itayd100]

I did this:

 

[KlausST]

Hi,

(I´m referring to the datasheet)

in my eyes if you want a 64MHz Frequency you need to buy a 64MHz Xtal.

What I see in the datasheet is, that the XTALs up to 30MHz work on fundamental frequency (if you could use them as 3rd overtone ones, it makes no sense that you can buy 64MHz XTALs)
and XTALs above 30MHz are designed to work on 3rd overtone.

Klaus

 

[andre_luis]

It is not clear from where you took there parameters for crystal, neither which BJT transistor were selected for Q1.

 

[itayd100]

I selected 2n3904 as Q1.
For the crystal parameters, I used this tool: **broken link removed**

 

[FvM]

Apart from reasonability of this application, you need a resonant oscillator circuit to suppress possible fundamental wave oscillations.

 

[itayd100]

Hey FvM,
I read about that. Where should I place the parts (inductor and capacitor)? What should be the size of them?

 

[BradtheRad]

This link is from a series of Navy electronics manuals. It has a few ideas about combining crystals and LC tank circuits.



Here is a simulation based on one of the schematics:

Notice the first pulse is sufficient to start resonating action in the 63MHz LC tank.

 

[Warpspeed]

Apart from reasonability of this application, you need a resonant oscillator circuit to suppress possible fundamental wave oscillations.

That is the important clue.
Overtone crystal oscillators always have a tuned circuit to peak the gain at the third harmonic, (or sometimes the fifth harmonic).
This is a pretty typical type of circuit:



Personally I would not bother, as you can buy 64Mhz oscillator module for less than a couple of dollars and be done.

**broken link removed**

 

[goldsmith]

I want to work with my crystal in 3rd overtone (64MHz).

I made the attached circuit and I can get just 21Mhz.
How can I get it working?


Thanks,
Itay

Hi Itay
have a look here , perhaps it helps you somehow :

https://www.edaboard.com/blog/1856/
And here of course :
https://www.edaboard.com/blog/1788/


Best Wishes
Goldsmith