GPS-Disciplined 10 MHz Frequency Standard / GPS-Based Universal Time Clock

Posted on Feb 7, 2014

As shown in the block diagram above, the 10 MHz signal is produced by an oven-stabilized 10 MHz crystal oscillator that is locked by a phase-locked-loop circuit (PLL) against the precision 10 kHz signal generated by the GPS receiver module. In addition to the 10 MHz signal, precision 10 kHz and 1 Hz signals are also output by the system. The 1 Hz signal is especially useful as a precise 1 pulse-per-second

GPS-Disciplined 10 MHz Frequency Standard / GPS-Based Universal Time Clock
Click here to download the full size of the above Circuit.

reference for clocks that can accept such input. The raw NMEAdata generated by the GPS receiver is sent to a RS-232 level converter and to a PIC microcontroller. The PIC decodes the data and displays exact location and universal time information. The RS232data are sent to instruments around my shack that can use it, for example for precision satellite tracking with my space-communications antenna array. The GPS receiver that I used is a surplusOEM unit made by Rockwell (information available here: Rockwell_Jupiter_GPS ). However, any other GPS module that outputs a GPS-derived 10 kHz signal may be used. The PLLcircuit (click on the figure to enlarge)was designed by Joe Ruggieri(AKA eBay Pyrojoseph) and constructed on a circuit board that he sells. The circuit connects directly to the 10 MHz OCXO and to the 10 kHz output from the GPS module. The circuit requires 12 VDC, which I feed from an external power supply. As shown in the following figure, the GPS-disciplined oscillator performs superbly as evidenced by comparing its output to that of my rubidium atomic clock reference :

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