Trimble ThunderBolt Timing GPS Receiver GPSDO
© Brooke Clarke 2008
Background
Description
Antenna
Power Supply
Start Up
ThunderBolt Monitor Program
IC Table
External Oscillator Option
Disiplined vs. Unlocked
Maintenance
Drawing
References
Links
Background
Trimble has been making GPS
receivers since the system has been in existence. They made
the Trimpack which was one of the first
GPS units used in Desert Storm. The U.S. then used the PLGR GPS receiver and now (2008) the DAGR.
But these GPS receivers were intended for use mainly as navigation
tools and only supported timing in the sense of frequency hopping
radios like SINCGARS. The Motorola
GPS receivers have had a precision time capability and the M12T+ is
very good at that (Motorola has sold the GPS receiver operation and
it's now part of i-LOTUS and
is sold by Synergy.
There are two first generation Trimble Thunderbolt GPS receiver
versions.
p/n 48050-61 for the metal cage 24 Volt
p/n 48051-61 for the board only that needs +5, +12 & -12 Volts
The board only in a metal box that needs +5, +12 & -12 Volts may
have been a custom part.
The first generation ThunderBolt receivers went out of production in
mid 2006 because of Rohas lead free EU rules.
The current lead free ThunderBolt
is
the "E" version. Although not a direct replacement for the
first generation timing receiver, it's very similar.
The Thunderbolt is what's called a GPS Disciplined Oscillator
(GPSDO). The internal 10 MHz oscillator has it's tuning voltage
controlled by the GPS time. The 10 MHz is divided down to provide
a 1 Pulse Per Second (!PPS) output. If the GPS signal is lost it
goes into holdover mode.
This is huge improvement over the old lab crystal oscillators that
needed to be manually tweaked (calibrated) every 6 to 12 months to
account for crystal aging. With the GPSDO the corrections are
applied automatically in real time as long as you have GPS
reception. A GPSDO is an excellent way to have a lab
frequency standard to drive test equipment that accepts external 10 MHz
references signals like counters, spectrum analyzers etc. The
1PPS signal is a good way to make precision time interval measurements.
Description
The unit shown here is from TAPR
and was part of the Time
Nuts mailing list group buy. They also have been on eBay (thunderbolt
gps) recently. It's the receiver only board in a metal box.
Antenna
The Trimble Trimpack GPS receivers
require
about 41 dB gain between the antenna and receiver and so will not work
with the common 20 dB gain antennas. But the ThunderBolt can work
with between 18 and 35 dB gain which covers most common antennas.
The treatment of the antenna and coax loss is not very good in the
ThunderBoltBook2003. There is a better discussion in the ThunderBolt
E
User Guide.pdf.
The antenna connector center conductor supplies +5 Volts to the antenna
so should NOT be used to power the newer 3.3 Volt GPS antennas.
Power Supply
The metal cage p/n 48050-61 version runs from a single 24 volt power
supply and inside has a power supply board that generates +5, +12 and
-12 VDC to power the receiver board. I expect that this is a very
clean power supply (but haven't seen data to support that yet).
The single board p/n 48051-61 and the metal boxed single board version
require +5, +12 and -12 VDC. It turns out that any noise on these
supplies (maybe not all three of them) degrades the performance of the
outputs as shown on the Allan plots (TVB Thunderbolt
PS Noise). That's why I'm using an HP E3631A triple output
lab power supply as shown in the photo at the top of this page.
The currents drawn are:
mAmps
|
+5
|
+12
|
-12
|
Cold
|
224
|
678
|
2
|
Warm
|
246
|
144
|
2
|
YMMV
Connector Pinout
TVB Power
Supply web page has pinout and connector info.
Photos below show real parts. The illustrations in the cataloge
are generalized drawings.
|
|
Molex
16-02-0103 female contact pins
|
Molex
50-57-9406 6 position shell
|
Molex hand crimp tool No. 63811-8700 (Mouser 538-63811-8700)
one
each for $321.98.
The Radio Shack tool works.
Start Up
When the unit does a cold start as delivered from the factory it will:
(1) warm up the oscillator (maybe 20 minutes)
During this time it can start locking
on satellites and down loading the almanac data
(2) do a self survey to learn the antenna position (maybe an hour)
(3) change from "start up" mode to "disciplining" mode
Recently a power failure shut down my HP triple output lab supply and
when I powered up the Thunderbolt it did not know the time and did not
find any satellites. Changing to a diferent antenna seemed to fix
it and when the first antenna was reconnected all seems fine.
ThunderBolt Monitor Programs
Tboltmon.exe
This
is
a
Windows program that allows setting up and monitoring the
operation of the ThunderBolt receiver. The program is not
required and can be disconnected from the receiver once you are happy
with it's settings.
The only yellow dot is the one for Leap Second Pending. When
first run there are a number of yellow dots. Although there is a
Tracking Status Window, it uses a text table to display the data, not a
polar graph like in the TAC32 program for the Motorola GPS receivers.
The ThunderBolt has EEPROM memory for it's key settings, called
segments in the monitor program. How the ThunderBolt boots up
depends on the contents of these stored segments.
If the factory default condition then on power up a self survey is
done. This requires some time operating in the 3D fix mode to get
an average position. If a precision reference position is stored
then it boots up without the self survey.
The timing Outputs area in the lower left displays the PPS error
(-17.64 ns UTC) so it looks like there is a sawtooth correction
available.
When the cursor is anywhere on the window and right clicked there are a
number of options relating to the serial port connection.
DSPMon_V1-53.exe
This
is the program that's used with the Thunderbolt E (although the manual
for the E version has information about another program). Once
you right click and set the serial port to COM 1 9600 8-N-1 it works
with the non E version. The Timing area has three data
fields compared to the Timing Outputs area of the Thunderbolt Monitor
program the new field is called PPS Quant error 0.0 ns. When run
with a non E version Thunderbolt this field is always 0.0.
General Note on Software
Each GPS manufacturer has their own proprietary binary data format and
it tends to stay the same for all their receivers. As each new
receiver is introduced it may also have some new commands but the prior
commands tend to be supported. So the latest version of the
software tends to work with all the prior receivers.
Timekeeper
This software keeps the PC clock aligned with UTC.
Lady Heather's Disciplined Oscillator Control Program - readme.html
- download
This program has a number of graphical
outputs.
A low cost GPS Monitor
- a hardware monitor
IC Table
The following ICs are on both sides of the PCB. If you can
help identifying them and/or supply a URL to data sheets please contact me.
| ID |
Mfg |
Function |
Marking |
Date |
| F2 |
GI |
GPS BP
Filter |
GI M37 |
|
| U01 |
CY |
128x8 RAM |
62128BLL-70SC |
0402 |
| U02 |
Trmbl |
GPS uC
|
F.W.=3.00 48051-30 |
|
| U05 |
ON |
Logic |
74HCU04A |
|
| U06 |
CSI |
Logic |
93C865 |
0341C |
| U07 |
generic |
512kx8
Flash Memory
|
29F400BB-120EI |
|
| U09 |
DS |
Thermometer |
DS1620 |
|
| U10 |
MACOM |
27 dB Low
Noise Amp |
AM50-002 |
|
| U14 |
TI |
Logic |
74AC174M |
35AYC8M |
| U15 |
? |
|
349 |
2105 |
| U17 |
Linear |
Quad Op Amp
|
LT1014
ISW N08316 |
0401 |
| U18 |
I |
RS-232? |
2321BE |
41Z1L |
| U19 |
TI |
Logic |
74AC04M |
3CC7EVK |
| U20 |
TI |
Buffer Amp
|
OPA692 |
|
| U22 |
Xilinx |
256
cell FPGA |
XC5202 |
|
| U411 |
Infineon |
GPS RF Tuner
|
PMB3332 |
0342 |
| U460 |
TI |
|
7301Q 3CT |
|
| U461 |
ST |
Logic |
74VHCT32 |
|
| U999 |
Sawtek |
Filter |
855242 |
009410 |
| Y1 |
32.768k |
RTC xtal
|
|
|
| Y2 |
3.6864 |
CPU xtal
|
|
|
External Oscillator Option
When you look at the bottom of the PCB (left side in photo at left) in
the space under the OCXO
there are two hole patterns like for a SMA, SMB, SMC or similar solder
in coax connector. That would be consistent with a 10 MHz signal
to the PCB and a tuning voltage signal to the external
oscillator. Note that one of the TSIP commands allows configuring
the tuning voltage parameters and is also part of the Tboltmon program.
Disiplined vs. Unlocked
When the oscillator is being disiplined it typically has more phase
noise than when it's free running for some time intervals. Each
GPSDO is different, but typically for time intervals shorter than 100
seconds you get better phase noise by turning off the
disiplining. For plots see TVB web page Locked vs Unlocked.
Maintenance
Others have reported that a bunch of "?" appear and the
unit does not seem responsive to the computer, but has 1 PPS and 10 Mhz
outputs.
These were caused by bad joints relating to the RS-232
connector or the RS-232 IC.
The RS-232 interface is only 3 wires.
Pin
|
Function
|
Voltage
|
2
|
Data Out
|
-11.3V
jumps once/second
|
3
|
Data In
|
0
|
5
|
Ground
|
0
|
Drawing
This is a pdf version of an Autocad drawing.
ThunderboltDwg.pdf It's a test
of the capability.
Product Idea
A DB-9 connector and shell holding a
PIC micro controller that monitors the serial data stream and lights a
LED(s) to show mode of operation, 1 PPS heartbeat and fault codes.
Note that the DB-9F connector only has TXD, RXD and ground
connected.
There are no other pins used so a jumper might be added internally to
bring out the 1 PPS, 10 MHz and to bring out a power supply(s).
Let me know if interested.
References
ThunderBoltBook2003.pdf,
142
pages) has many missing Adobe bookmarks, so that method of
navigation does not work, so for now use the Table Of Contents.
Tboltmon.exe
is the PC program to monitor and control the ThunderBolt.
Links
ThunderBolt FAQ, Power Supply
Connections, Power Supply
Noise, Phase Noise
Comparison, Locked
vs
Unlocked, on TVB's web site
Johm Miles Notes on
Trimble Thunderbolt performance and modifications web page confirms
the external oscillator jacks.
Back to Brooke's PRC68, Products
for Sale, Navigation, Military
Information, Personal Home
page
05564 hits since November 08 2008 page created 6 Nov 2008.
This
is
a
Windows program that allows setting up and monitoring the
operation of the ThunderBolt receiver. The program is not
required and can be disconnected from the receiver once you are happy
with it's settings.
