Trimble Palisade GPS 1PPS time source

Trimble Palisade GPS 1 PPS time source

Much less expensive than a rack mount GPS receiver and much easier to use than an OEM GPS receiver board, the Trimble Palisade is a self-contained antenna and receiver built into one weather-proof plastic housing.

On board power regulation.

Interface signals are RS-422 not RF not coax not RS-232

Trimble Palisade antenna/receiver module shown with SIM board

Palisade size comparison with HP 58532A and HP 58504 antennas

SIM interface board: serial port B, serial port A, 1 PPS BNC

1 PPS Output waveforms

The Trimble Palisade is a self-contained GPS antenna and receiver which generates a UTC synchronized 1 PPS output, automatically performing cold-start and auto-survey as necessary. Two RS-422 serial interfaces and one RS-422 1 PPS interface are provided. An optional SIM (Synchronization Interface Module) is available which converts the RS-422 serial lines to DB9 RS-232 and the RS-422 1 PPS to a TTL pulse on a BNC connector.

fast rise time, 3 V, rising edge 1 PPS output

The Palisade antenna/receiver module produces a RS-422 differential 1 PPS output on Palisade connector pins 11 and 12 which become DB25 pins 9 and 21.

RS-422 DB25 pin 9 (1 PPS transmit minus)

RS-422 DB25 pin 21 (1 PPS transmit plus)

Pins 9 and 21

By contrast here's a view of serial IO pins

How to use the Palisade

MMP refers to the concentric connector on the bottom of the Palisade.

Apply 24 VDC (actually 9 to 32 is fine) to MMP pin 1 (red)
Ground is MMP pin 9 (black)
Ignore RS-422 Port A lines (violet, orange, brown, yellow)
Ignore RS-422 Port B lines (white, gray, green, blue)
1 PPS output plus is pin 11 (orange/white)
1 PPS output minus is pin 12 (black/white)

Startup procedure

Apply power
Wait about an hour for unit to acquire satellites and perform site survey
1 PPS will start working at this point

Do not ground either 1 PPS output. It is safe to use one side of the 1 PPS (e.g., pin 11) as your 1 PPS signal using ground as a reference. You will then get a 1 VDC to 5 VDC rising edge lasting 1 us each second.

You can use the PC program PalisadeMonitor.exe to monitor the GPS receiver. For this you need to convert the port B signals to RS-232. This can be done with commodity converters or the special Trimble SIM box.

The antenna should be mounted on a roof with a decent view of the sky. But for quick testing placing the antenna near the ceiling of my upstairs lab works pretty well.

indoor ceiling antenna location

Some views of RS-422 1 PPS output

Black/white to outer shell of BNC (ground). Orange/white to inner pin (signal)

RS-422 1 PPS raw output (approx 12 Vpp)

RS-422 1 PPS w/ 50R term (approx 5 Vpp)

RS-422 1 PPS to 50R to DC-block (0-5V)

RS-422 1 PPS to DC-block to 50R (messy)

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