Very good !
I use an STM32F CPU with it's main input clock driven from a 10MHz?OCXO 143-141 (plenty of cheap used ones on aliexpress), I feed the filtered long wave RF signal (from a small tuned ferrite antenna) from either the french 162kHz caesium referenced transmitter or the UK BBC 198kHz rubidium referenced transmitter into one of the ADC ports. I then do software PLL I/Q (in firmware) and use the CPU's DAC output to correct the 10MHz OCXO-143 oscillator. It's as stable as the either of the two transmitters (which are regularly checked/calibrated once a week I believe).
The 10MHz OCXO output I also feed into an Si5351 chip (Si5351's also work with 10MHz clock input if you want) to generate any other frequency I want up to 160MHz (SDR reference input's, frequency counters etc).
