I did it for $25...  $7 for the GPS+antenna module,  $3 for an  Arduino chip on a PCB with proto area from China (should have bought a lot more when they were available),    $10 for a small ovenized 5V TTL output OCXO (also should have bought a lot more),  and $5 for misc parts (OK, beer money not included in the BOM).  Batteries not needed, powered off USB.  It worked better than I expected... not Tbolt quality, but not too shabby for a thee-day weekend hack.    $50 (and a lot of work)  is certainly doable for a decent home-brew GPSDO.

On Mon, Mar 20, 2017 at 4:14 PM, Mark Sims holrum@hotmail.com wrote:

Hi Mark,

Did you use the Arduino's PWM output plus a LPF for the DAC, or a separate
DAC? If PWM, did you have problems with noise or sensitivity to the
USB-provided supply voltage?

Also I have found that not all computer USB ports can supply enough warm-up
current for a 5V OCXO. Or did you use a hefty USB charger and miss out on
the ability to get logging info back over the USB port?

--

--Jim Harman