About the HP Z3810A

The Hewlett-Packard Z3810A is a GPS-disciplined frequency standard that uses signals from the Global Positioning System satellite constellation to discipline an internal quartz oscillator. By continuously comparing its internal oscillator to the atomic clocks aboard GPS satellites, the Z3810A achieves frequency accuracy that approaches that of a cesium beam standard -- at a fraction of the cost and complexity.

Dual Receiver Installation

This installation features two Z3810A receivers mounted in a standard 19-inch equipment rack. Running dual receivers provides several advantages:

• Redundancy: If one receiver loses satellite lock or experiences a failure, the second continues to provide accurate time and frequency outputs without interruption.
• Cross-checking: The outputs of both receivers can be compared against each other and against the cesium beam frequency standard to detect any anomalies or degradation in performance.
• Multiple outputs: Each receiver provides independent 10 MHz and 1 PPS outputs, allowing multiple instruments or clock systems to be driven simultaneously without splitting signals.

Power Supply

The power for the GPS receivers comes from a repurposed PBX (Private Branch Exchange) telecommunications power supply. PBX power supplies are ideal for precision instrumentation because they are designed to provide extremely clean, well-regulated DC power with minimal ripple and noise -- characteristics that are important when the goal is frequency accuracy at parts-per-billion levels.

Role in the Collection

The Z3810A receivers serve as the GPS time reference for the collection, providing a direct link to the UTC time scale maintained by the GPS satellite system. Their outputs are compared against the HP 5061A cesium beam frequency standard and used to verify the accuracy of all clocks in the collection. The GPS-disciplined signal is also available to drive the computer-based master clock system that synchronizes the Self Winding Clock Company secondary clocks throughout the house.