titaniummines
Newbie level 3
I need some help with a crystal oscillator which is being very stubbornand not oscillating. It is part of a PLL and has a crystal with 63.9151MHz written on it. The manual says the crystal is a 3rd overtone which is not surprising at this frequency. The circuit seems to be a Colpitts oscillator with a few capacitors switched in and out in order to pull the frequency slightly. The transistor tests ok in a transistor tester so I removed the crystal itself and built an oscillator on breadboard. This works fine with the 63MHz crystal but oscillates around 21.8MHz which is probably the fundamental. However back in the transceiver it's back to being dead again, I'm guessing the circuit is dampening oscillation at the fundamental hence why it's not working.
My question is can a crystal be faulty in such a way that it stops oscillating on the overtone yet will still work at the fundamental? It seems unlikely a passive component in the circuit is at fault.
My question is can a crystal be faulty in such a way that it stops oscillating on the overtone yet will still work at the fundamental? It seems unlikely a passive component in the circuit is at fault.