Generally, a crystal is a fundamental frequency below about 15 MHz...

Above that, the quartz crystal starts to be thin enough to make it
fragile and prone to being broken. There are ways to make a fundamental up
to a hundred MHz or so, but these are usually very expensive crystals and
pretty rare.

So, it is most likely that the 27 MHz was the third overtone of the 9 MHz
fundamental frequency.

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A broadband amplifier type of oscillator may have enough gain, and
perhaps a parasitic resonance or so to make it tend to run on an overtone
frequency. Generally, build a good circuit on a solid ground and keep the
feedback loop set up for low gain on the feedback.

Excessive gain in the system will tend to cause 'strange' results and
your experience is not all that surprising.

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Given that Citizens band frequency crystals used to be fairly common, I
would guess this is what you have.



Jim Pennell
N6BIU