I have oscillator (216 MHz, PECL) connected to differential mux (PECL) on a digital board and fails. I get only noise. Same oscillator works on another analog board. Set up is so simple. What could be wrong with it? Any debugging suggestions?
Check if the power supply is properly decoupled, and make sure that all the connecting tracks have 50 ohm impedance, and terminated with 50 ohm resistors to Vtt (Vcc-2V).