[Mark] wanted an accurate frequency reference for his electronics lab. He specified some requirements for the project, including portability, ability to work inside a building, and low cost. That ruled out GPS, cesium standard clocks, rubidium standard clocks, and left him looking for a low cost Oven Controlled Crystal Oscillator (OCXO).
The Low Cost 10 MHz Frequency Reference is based around a Morion OCXO. These Russian oscillators are available from eBay second hand at about $40 a pop. With a stability well within the requirements, [Mark] order a few.
The next step was to stick all the components in a box. The two OCXOs in the box need about 3 amps to heat up, which is provided by a 12 V PSU. For portability, a sealed lead acid battery was added. The front panel shows the supply voltages, switches between mains and battery supplies, and provides connectivity to the OCXOs.
Since OCXOs work by heating a crystal to a specific temperature, they can use quite a bit of power in the heating element. To increase battery life, a neoprene foam insulator was wrapped around the OCXOs.
For less than $100, this portable tool will aid in calibrating equipment or creating very accurate clocks.


The basic box is built from a single sheet of 7mm plywood. The front work area is a smaller piece of 12mm plywood. Working with 7mm plywood did prove to be a challenge – [Tez] had to use some very small screws for his hinges. The basic box construction was easy though – [Tez] used a pneumatic nailer and PVA (wood) glue.
A few years ago, [Michele] built a mobile device with a touch screen, a relatively powerful processor, and a whole bunch of sensors. To be honest, the question of why he built this was never asked because it’s an impressive display of electronic design and fabrication.
Alright, 3D Printers exist. They’re machines you can simply buy for a few hundred dollars, set them on your desk, and have them start churning out plastic parts. A little pedestrian, isn’t it? How about something you can take into the field for a client, and print out some new parts right there? How about sending a printer to the latest humanitarian crisis? After all, all those humanitarian uses for 3D printers we’ve been hearing about won’t do any good without a 3D printer.
