In article , PaoloC
writes
Hi.
I have spent part of the weekend trying to resonate al old CB XTAL at
its fundamental frequency.

The XTAL is labelled 27.125 MHz, with a fundamental of about 9.041 MHz,
which falls into 18m HAM band when multiplied by two. I assume 27MHz
XTALs are 3rd overtone.

Since the circuitry is/will be digital, the oscillator is one gate of a
74HC14. 470ohm resistor from gate output to the parallel of 1Mohm//XTAL.
10pF and 33pF (from the junkbox) capacitors to ground on each side of
the XTAL.

No oscillation (I have no oscilloscope, I use my HF receiver to
troubleshoot oscillators at known frequencies).

If I replace the XTAL with a 10.000 MHz rock the oscillation is loud and
clear.

I have never built something with an overtone XTAL. I know that I need
an output resonating circuit if I want to extract the 3rd harmonic. Do I
need the same if I want the fundamental?

Are overtone XTALs "harder" to resonate?

Are those old CB XTALs 3rd overtone?

I assume my 27MHz XTAL works. :-) Thanks in advance for all suggestions,
Paolo IK1ZYW
Could be a 27 MHz fundamental or 10.7 above or below 27MHz.
--
ddwyer