GPS Disciplined Frequency Standard

GPSDO photo
GPSDO testing

Modifications and updates for the GPSDO described in Homebrew, Radcom March 2008.

This is the support page for the GPSDO described in the RSGB magazine RadCom for March 2008. As this has become one of those never-ending projects, I have decided to start a web-page dedicated to this project and GPSDOs in general.

This project was inspired by the excellent GPSDO designed and built by James Miller G3RUH and another Rockwell Jupiter based GPSDO project by Andy Talbot G4JNT.

gpsdo digital circuit
Original GPSDO schematic

10MHz oscillator
Simple 10MHz crystal oscillator

Power supply
Power supply

Interface circuit
1pps LED and TXD serial interface

Inside view
Inside the box

The original 10MHz crystal oscillator has been replaced by a NDK NAC3015A OCXO. Most OCXOs have a frequency control input. A DC voltage applied to this input can be used to adjust the output frequency of the OCXO over a small frequency range. The control range is typically just +/- a few Hz, and rarely more than +/- a few tens of Hz.