Nick Sayer created this GPS disciplined high precision oscillator to generate a very accurate 10 MHz square wave:
GPS Disciplined xCXO
The basic design of the project centers around either a VCTCXO – a Voltage Controlled Temperature Compensated Crystal Oscillator or a VCOCXO – a Voltage Controlled Oven Controlled Crystal Oscillator.
FE-5680A GPS Discipline Module v1.6.3
Geppetto Electronics sells the module on Tindie:
GPS Disciplined xCXO
A GPS disciplined 10 MHz frequency standard – ±1 ppb or ±0.1 ppb
OSH Park 