Crystal 3rd Overtone - which frequency?

[dohzer]

If a crystal datasheet lists that a family of crystals can work in either fundamental or 3rd overtone modes, and then lists different frequencies for both, which frequency limits do I use.
Basically I want a 50MHz crystal that I can use to generate a 150MHz output in 3rd overtone mode.

So, for instance, looking at the Abracon ABM3 family of crystals (link to .pdf datasheet) it lists the following frequency range:

[B]Fundamental Frequency Range:[/B]
[B]Min:[/B] 8.000 MHz
[B]Max[/B]: 54.000 MHz
[B]3rd Overtone Frequency Range:[/B]
[B]Min:[/B] 54.100 MHz
[B]Max:[/B] 80.000 MHz

Does this mean that:
a) The largest frequency I can generate using a 3rd overtone frequency is 80MHz? i.e to do this I would select a crystal with a fundamental frequency of 80/3 = 26.66667MHz.
b) The largest frequency I can generate is 240MHz? i.e. to do this I would select the 80MHz oscillator and in its operating mode it would generate 80*3 = 240MHz.

I would have assumed I could use any of the fundamental frequency crystals to generate a 3rd overtone, but the fact that 8*3 = 24MHz falls outside the minimum third overtone frequency makes me think this is not possibly, and also leads me to assume that I can't generate a 50*3 = 150MHz frequency output.

 

[erikl]

a) The largest frequency I can generate using a 3rd overtone frequency is 80MHz? i.e to do this I would select a crystal with a fundamental frequency of 80/3 = 26.66667MHz.

Right!

I would have assumed I could use any of the fundamental frequency crystals to generate a 3rd overtone, but the fact that 8*3 = 24MHz falls outside the minimum third overtone frequency makes me think this is not possibly, and also leads me to assume that I can't generate a 50*3 = 150MHz frequency output.

Right, too!