I still have one of the Mutek HF Transverters- use it with an IC202.
One day, I must measure its performance- by ear it’s rather impressive.
Totally agree that a good VHF xtal oscillator is the best, low cost, non-surface wave device way to a clean microwave signal. Frequencies around 100 MHz (5th overtone) seem best.
The PLL to lock the frequency to 10MHz reference has to be fairly narrow bandwidth so as not to spoil the phase noise performance.
The block diagram of a good signal generator shows the approach, though some synthesis schemes are of head-aching complexity to obtain continuous low-spur coverage.
The other neat technique I’ve seen is the use of high overtone xtal or acoustic wave filters to clean the noise sidebands off multiplied sources- was standard practice in microwave point to point links.
Alwyn Seeds, Director
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