Technical Topics



Trimble GPS Frequency/Time Receiver

Trimble made a GPS receiver that at first glance appears almost identical to the HP Z3801A. The front panel LED indicators are labeled the same and are in the same physical order as the HP receiver. The front locking knobs and handle appear identical to the HP Z3801A. This receiver may have been a second source to the Z3801A because it appears to be a physically identical outside form fit. The internal circuitry is different however.

The Trimble GPS receiver rear panel shows a DC power connector similar to the HP. The input power requirement according to the rear panel is "plus 27 VDC or minus 54 VDC". A DB25 I/O connector, a GPS antenna connector, and a 10 MHz BNC frequency output connector are visible.

The Trimble receiver appears to be a highly integrated design with plenty of room left over in the Z3801A size enclosure. There are no stacking circuit boards or interconnecting cable clutter. The DC to DC converter has a single main module and discrete capacitors located near the front panel. The integrated control logic and Trimble GPS receiver occupy the main circuit board. The 10 MHz oven oscillator is a dual design made by CQE (OCXO DOC 1272).

The receiver uses the Trimble Standard Interface Protocol (TSIP). HP command and control software will NOT work with this unit.

This receiver is probably a predecessor to Trimble's Thunderbolt GPS Receiver. If you cut the PC board into functional sections, it appears almost like Trimble's current Thunderbolt product offering.

Printed specifications from the manual:

8 Channel - Independent tracking - L1 C/A code
Acquisition threshold - 10db to 60 db at input type "N".
Tracking threshold - 5db to 60db
Jam immunity - -110Db at L1 at input type "N".
Baseband threshold - 2 bits (I and Q)
Update rate - 1Hz nominal output (5hz internal)
Frequency accuracy - <2E-12 one day average
<2E-10 any interval
Uses a 20 Bit D to A converter. - RS-422
States - 24-60 Vdc - 27Vdc recommended. Has the 5Vdc for the antenna

Thanks to Dave Jones, K4DLJ for the specification info.

Copyright © 2001-2016 Bill Jones, K8CU