Philip BraggPondering what to do with a nice chunky 2.048MHz crystal from a broken HP 3764A, I decided to make it generate 1216kHz for further Inovonics experiments. Their old gear often used this frequency as a master clock. #electronics
I'm using the normal 4000 series CMOS here, instead of the 74HC4000 series that I've been using recently. The 4000 series has some interesting quirks and varies enormously between manufacturers. You can't do the diode programming trick on Harris and TI 4024s at even a sedate 1MHz and the NS part I've used here still needed 56pF loading on the reset pin to work reliably. 74HC parts will do this at >30MHz, a huge difference in performance.
The circuit divides 2.048MHz 4011BE crystal oscillator down to 64kHz in a 4020 and this is sent to a phase-frequency detector in a 4046BE which divides its own VCO by 19 in the 4024 before comparing it with the 64kHz reference. There's a loop filter to stop the whole thing shaking itself off the spectrum and that's about it. Yes, two of the 4011 gates aren't connected to anything yet. Bad me!