Overtone crystals?

[walker1]

I will be needing a 1st LO at around 48 MHz. That seems to be in the 3rd overtone area.

But a strange question just popped up.

Does every crystal have useful overtones or do they have to be specifically cut to have that?

I mean, could I take any, say, 16 MHz crystal, use in a 3rd overtone oscillator and get something out in that band?
(not necessary the same frequency, I guess, but ... )

Unfortunately, I am somewhat out of my league here. 10 MHz analog is usually my upper limit

 

[zappedagain]

Overtone crystals sometimes have different stuctures. Randall Rhea has some good books on crystals and oscilators.

John D

 

[benta]

You might consider using a PLL controlled oscillator, they are often better in terms of phase noise.

Benta.

 

[walker1]

Yes, I have started looking into PLL oscillators. Even before posting the above.

They are all SMD, however :-( And they consume loads of power. (30 to 75 mA @ 3.3V) The later could be a problem, as the unit is battery powered.

On the other hand I can get the frequency, I really need. in the 144 - 150 MHz band, that is!

 

[zappedagain]

As power is a concern overtone crystals are the way to go; battery powered radios have been using them forever. Again, I suggest Rhea's book if you want to get into this. Crystal designs do have some gotchas that you have to know about to work around.

John D