The Z3801A GPS-Disciplined Oscillator

I am using a couple of HP Z3801A GPS-disciplined oscillators as my primary frequency standards. These devices use a Motorola Oncore GPS to discipline an HP10811D oven-controlled crystal oscillator. Although they were designed for use in digital cellular base stations, and are officially specified only to meet the required performance for that service, they are essentially identical to the HP 58503 "SmartClock" and perform very well indeed. They can keep the 10MHz oscillator on frequency within a few parts in 1012. The SmartClock system learns the aging rate of the oscillator and can keep the frequency close to the mark even if the GPS signal goes away for up to a couple of days.

Check out for some great info on the Z3801A.

There's a really nice software package called GPSCon that hooks to the Z3801A's serial port and provides all sorts of performance data with a nice graphical output that can automatically be turned into a web page. Unfortunately for me, it's a Windows program and I've now converted all my hamshack and workbench computers to run Linux.

To solve that problem, I've written some Linux tools for logging Z3801A data; check the link below for details.

More Z3801A Stuff