Technical Topics



HP 58540A GPS Time and Frequency Reference Receiver

HP 58540A GPS Receiver

A First Look

This is a tiny receiver! It is not much larger than a standard 3.5 inch floppy disk, and it weighs about one-pound. Threaded mounting holes on the enclosure bottom are provided for receiver mounting. It appears very similar to the Datum Starloc II GPS receiver, since the cabinet has essentially identical dimensions.

58540A Front Panel

Front Panel

-- BNC connectors for 10 MHz out, One PPS out
-- TNC connector for GPS antenna input
-- DB9 for RS-232 serial control
-- Dual color Alarm LED
-- Three pin Amp Mate-N-Loc power connector for 24 Volts, 1 Amp max input. Mating connector is AMP 350766-1 (male shell). Pins are AMP 350690-1.

Electrical Specifications

Frequency: 10 MHz Frequency accuracy: less than 1 x 10-11 for a one day average when locked to GPS.

Time: One PPS Absolute accuracy less than 110 nsec with respect to UTC when locked to GPS.

Serial Port

Serial protocol is SCPI. Factory default 9600 baud, 8 data,1 stop bit, no parity.


Two small circuit boards are inside the receiver enclosure. The bottom one is the DC to DC converter. It changes the plus 24 Volt input into plus 5V and plus 12V.

Inside 58540A

The top board is the GPS receiver itself. A shielded 8 channel GPS receiver, an oven oscillator, and surface mount control circuitry is located on the board. The circuit board has mounting holes and footprint patterns for four different oven oscillators. The oscillator used on this example is the SC cut MTI 230-0801 10 MHz oven oscillator, similar to that used in the HP Z3816A.  

.Inside 58540A


I like this receiver. It appears to be a worthy time and frequency reference. The performance is probably along the lines of the Z3816A or better. The internal firmware is oriented more towards the use of the receiver as a movable device rather than a fixed position 10 MHz frequency reference.

An examination of the manual showed that no commands exist for examining internal parameters like oven EFC, One PPS vs GPS Time Interval, or Predicted Uncertainty. Without these commands in the receiver firmware, plotting and control software such as GPSCon Pro will function well in handling the basic receiver commands, but the graphing and plotting portions of the software will not work. The receiver simply does not supply what is required.

Also, the receiver does not offer a Status Command like the Z3801A and Z3816A receivers use, so the familiar screen status dump is not displayed.

If the 58540A is the ONLY receiver type you will be using, perhaps you are best served by using a simple serial communications program such as HyperTerminal. The free Symmetricom SatStat software will do the same thing for you.

Thanks to Mike Pinault, W7GHZ for loaning his receiver.