The "Brain" is a Bluepill ....
STM32Based $60 (w. coupons) - 10MHz "good enough" GPSDO
https://www.aliexpress.com/item/1005008144934326.html?
OCXO - Isotemp 143-141 - Sine out
EEvblog thread - Now about the alternate fw
https://www.eevblog.com/forum/testgear/ ... by-bh3sap/
Alternate fw - Github - Original author (sleeping ?)
https://github.com/dankar/gpsdo-fw
Alternate fw - Github - Forked , and active/current.
https://github.com/fredzo/gpsdo-fw
Does work quite ok - But it's not a Tbolt or HP
But 0.1..0.2 ppb seems acheivable.
Output is an OpAmp buffered Sine - 50R.
Runs off 8..12v (Or whatever you feed the 7805CV and can "Cool" ... lower is better, as the rest is burned up in heat in the 7805)
Could be usable for portable .... And might even run off the car battery, check case bottom for excess heat from the regulator.
Edit attached fredo_ firmware v0.1.13 binary, for someone not fluent in git/cmake
.