Trimble ThunderBolt Timing GPS Receiver GPSDO
© Brooke Clarke 2008
ThunderBolt Monitor Programs
iCruze Monitor - iCruze
Monitor 8051 PCB
Resistor Select Options
External Oscillator Option
Disiplined vs. Unlocked
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
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
The unit shown here is from TAPR
and was part of the Time
Nuts mailing list group buy. They also have been on eBay
gps) recently. It's the receiver only board in a metal
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
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
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
The currents drawn are:
Note: The HP E3631A is a very poor choice of power supply
because whenever there's a power brownout or blackout it forgets
it's settings and when power is restored comes up with the outputs
turned off. I have an HP 6236A power supply on order that has
manual knobs and will retain its settings after a power failure.
Power-One HTAA-16W-A Power Supply
A triple output supply rated:
Out: +5 VDC @ 2A
+/- 9 - 15 VDC @ .4A
All the wires need to be removed and replaced with an AC
line cord and a cable & connector to mate with the
Supply web page has pinout and connector info.
Photos below show real parts. The illustrations in the
cataloge are generalized drawings.
16-02-0103 female contact pins
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.
When the unit does a cold start as delivered from the factory it
(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
The Mode is (1) Power Up, Activity is (1) Osc Warm-up, DAC Voltage
is 0.000000, BUT
all the indicators are green.
ThunderBolt Monitor Programs
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
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
When the cursor is anywhere on the window and right clicked there
are a number of options relating to the serial port connection.
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.
This software keeps the PC clock aligned with UTC.
Lady Heather's Disciplined Oscillator Control
Program - readme.html
This program has a number of
||Prior to doing the screen
dump I pressed
t (time and temperature control),
Z (time zone) and
GMST (Greenwich Mean sidereal time),
but something is wrong since the time display is not
incrementing every second, more like once every 25 seconds!
|To get this screen dump from
a full screen image I pressed <CTRL><Print
Screen> then F11 to go back to a LH window. But
that caused 3.0 beta to crash and bring up the report an
error window WIN XP SP2.
Click on the image (17:14:47) to see the full size version.
A low cost GPS
Monitor - a hardware monitor
This is based on A low cost GPS Monitor
||Available from fluke.l
Power Supply Voltage: 5.0 Red=+
It turns out that this is one of the newer (Dec 2009 and
later) units that has an on board 78D05 regulator on the
samll PCB near where the 4 wires are soldered to the
board. These units need at least 7 VDC to work and
will work fine from +12 VDC.
|A T10 Torx bit is needed to
open the case. The lower PCB is the 2x20 LCD and the
daughter board is the custom uC for the Thunderbolt.
To the right and above where the wires are soldered you can
see a group of 3 pads, two rectangular with a trace between
them. The 78D05 is there on the other side of the
Since the display is on a cable it can be located where it
can be seen not where
the Thunderbolt is located. This makes the
display much more useful.
happened, the display is now blank? It is
dead! I think either static
applying 6 VDC to the input (adjustable lab supply) since
there's no input regulator. Working fine on
on +12 V input. When I turned the supply down from 6
to 5 V that
caused the 78D05 to drop out, turning it off.
|The top line displays either
GPS or UTC time & Date depending on how the receiver is
set. The second line shows:
No Message if it's not connected to the serial port of the
Thunderbolt, or alternating:
ACT: Phase Lock
RX: Overdet Clk
GPS: Doing Fixes
DAC V: 0.4874
|iCruze Apr 2010 Broken Again
April 2010 - the iCruze Thunderbolt monitor no longer
displays No Message or anything else. This is the
display and is no related to the RS-232 input. Don't
|The problem may be static zap
to the RS-232 connector since I was using it without the
iCruze Monitor 8051 PCB
|The Voltage regulator (Q2) is
a 78D05 and D1, D2 & D3 are 000 Ohm resistors which
means the C8051F330 uC may be powered by a voltage that
exceeds it's specs.
|21 Nov 2014 - Comment from
"If you refer to the picture of the microprocessor board,
you will notice that the locations marked D1, D2 and D3 are
populated by zero ohm resistors. That means that the 3 V
microcontroller was powered from 5V. I am actually amazed
that they worked at all, let alone worked for a while.
It is a shame that fluke.l saved on the cost of 3 diodes
that way. The 1N4148 is $.02 at Mouser in 25 pieces lots.
- Didier KO4BB
What I did (and I've mentioned this before) is to replace
zero ohm resistors with one red LED. The forward voltage
about 1.7vdc so it makes a pretty nice zener, and you have a
indicator to boot.
|Tunderbolt GPS iCruze Monitor
Replacement CPU Board
|This is the newest CPU board.
Wouldn't you know that I removed the header pins from the
The wire colors are my best guess.
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
||GPS BP Filter
||512kx8 Flash Memory
"0310D1" = rev D ( good)
the "E" rev has poorer resolution
||27 dB Low Noise Amp
||Quad Op Amp
|| 256 cell FPGA
||GPS RF Tuner
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.
Resistor Select Options
|brings 10us wide PPS out to pin 6 (DSR)
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.
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
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.
This is a pdf version of an Autocad drawing. ThunderboltDwg.pdf
a test of the capability.
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
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.
142 pages) has many missing Adobe bookmarks, so that method of
navigation does not work, so for now use the Table Of Contents.
is the PC program to monitor and control the ThunderBolt.
Supply Connections, Power
Supply Noise, Phase Noise
vs Unlocked, on TVB's web
Johm Miles Notes
on Trimble Thunderbolt performance and modifications web page
confirms the external oscillator jacks.
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