[time-nuts] Trimble/Nortel GPSTM (NTGS50AA) - working with Lady Heather.

Sam lists at digitalelectric.com.au
Mon Apr 16 00:23:14 UTC 2012


There was some discussion in Dec 2011 regarding the Trimble/Nortel GPSTM (NTGS50AA) which fizzed out after it was mentioned that Lady Heather would not work with these units. I was undeterred and purchased some anyway.

I have started playing around with these and have discovered that by asking it Sat status (0x10, 0x3C, 0x10, 0x03) at ~300ms intervals the unit will start streaming data after a few seconds. Once the Trimble is in this state Lady Heather detects the GPSDO and seems to work normally... Except the TC and DAMP fields which are reported as 0.0 and GAIN which is reported as -3.500 Hz/V (Tboltmon reports the correct values) I have read that this also happens with older Thunderbolts?

I have written a small Windows app (available on request, off list) that sends the required packets to the GPSTM and by wrapping it in a batch file I have it opening Lady Heather once the unit is in the required state. (Only required once, or after running Tboltmon)


Details of my 3, Trimble NTGS50AA's are:

Firmware:
App: 2.68  - 16 Dec 2004
GPS: 10.4 - 15 Dec 2004

GPS receiver has 8 Channels.

Default disciplining parameters as reported by Tboltmon:
Time Constant (sec): 100.0
Damping: 1.2
Ko (Hz/V) 1.20
Min Voltage: 0.0
Max Voltage: 6.0
Initial DAC Voltage: 3.000000
Jam Sync Thresh (ns): 0.0
Max Freq Offset (ppb): 45.0

These GPSDO's uses the Trimble 34310 DOCXO which I think is the Vectron OC-050?

There are 4 SMB RF connectors on the main board:
1. GPS Antenna Input
2. 10.000 MHz Output
3. 9.834 MHz Output
4. 0.5 Hz (Even Sec)  PP2S Output. Unfortunately requesting the unit to output 1PPS does nothing. (yet)

The 9.8304MHz output may be handy.. divided by 300 it's 32.768 KHz ;)

Power Supply:
The NTGS50AA requires 36-75 VDC (48V nominal) and has a on-board Lucent DC-DC converter to supply the required +/-12 and +5 volts.

Serial Interfaces:
Port A is RS-422 @19200 SCPI (available on the 110 pin connector on the main board)
Port B is RS-232 @9600 TSIP (DB9 connector on Breakout board)

LED indicators:
There are 5 LED's on the breakout board that contains the DB9 connector.
1. Power
2. Not used, but switch-able via software
3. Not used, but switch-able via software
4. Lock
5. Holdover

Temperature Sensor:
DS1620 Rev D

Jumpers:
There is a 8 pin header (JP1) on the main board that would accept 4 jumpers.. I haven't tried them but it is tempting to see what happens when I enable them.


//Sam



More information about the time-nuts mailing list