[time-nuts] frequency reference for portable operation

[gary]

I haven't researched this yet, but the SDR crowd is using GSM and LTE 
for tuning their sample clocks.

> https://github.com/steve-m/kalibrate-rtl
> https://github.com/Evrytania/LTE-Cell-Scanner


I have no idea what kind of accuracy you can get from a tower.