Formerly known as Nortel plc, a subsidiary of Northern Telecom Inc of Schaumburg, Illinois, USA, the company was acquired by Bowthorpe plc in 1997 and renamed Global Simulation Systems Ltd (GSSL).In 2000, the company changed its name to Spirent Communications (SW) Ltd.
A range of simulators has been developed by Spirent Communications for testing GPS equipment.The STR 2760 multichannel GPS simulator is supplied as a turnkey system including the computer workstation, signal generator and all operating software. The unit can be configured for C/A code, at L1 and L2 and, with the SAAS upgrade kit (for authorised users), Y code simulation. Up to 20 channels can be installed in one chassis. The simulator can also be supplied or upgraded for Differential GPS and attitude testing.
Other options for the STR 2760 include a multimode, multichannel jammer, closed-loop real-time upgrade, Ethernet interface (for aiding and logging data), various receiver interfaces and Wide Area Augmentation System (WAAS) simulation.The STR 2720 and STR 2775 are single-channel GPS simulators developed for maintenance and production testing. These units enable GPS receivers to be checked and provide the opportunity for automated testing of equipment.
The Blue "Host" connector is HP-IB (IEEE-488) interface to control computer
The fan runs on 24 VDC.
Cage Wiki: VMEbus
|VME GPS I/O card
||This card is the source for
the ribbon cable that drives the front panel LCD.
In the lower left are 2 ZN439 8-bit A to D converters.
That means the "58" and "59" coax cables are inputs to the VME system.
On this, and I think all other, VME cards the upper left connector is for the analog GPS signals
and the upper right connector is for the digital intercard communication.
|VME bus L1 P-Code Sig
||The VME cards for L1 and L2
appear to be identical in terms of their layout and chip
Although I haven't checked my guess is that there might be differences in the ROMs.
|VME bus L2 P-Code Sig Gen
||In the upper left there are
4 each AD9713B
- 12-Bit, 80 MSPS, TTL Compatible DAC
just below them are 4 each MCM62974 - 12 Bit Synchronous Static RAMs
In the rwo below them are 4 each "NCO-CK 50C" (guess) Numerically Controlled Oscillators
at the bottom of the VME card are 2 each CDGEN3 50C (guess) Carrier Data Generators
|MVME 143S-2 Motorola VME
CPU board with STR2760 ROMs
|This is one of the two CPU
cards in this system. Probably one for L1 and the
ohter for L2 signal generation.
The black box is a power supply rated 5V/60A, +12V/12A, +5V/12A.
There is continuity between the line cord and the 110VAC input, but there appears to be no output.
The PCB for the front panel must be a standard unit that supports a number of LED/Buttons
and this implementation just has the LCD.
To get to the input fuse inside the MML 400 power supply it's necessary to:
The input 120 VAC is rectified (how?) to DC less than 200 V.
That's used to power an oscillator that drives T1 primary.
T1 secondary powers the output modules.
There are 6 Printed Circuit Boards.
Line Hot -> Fuse FS70 half of L70 -> Main Board
Neutral --> 110 ----> half of L70 -> Main Board
passes MLU+, MLU- & 110(dot) to Main Board
Line Hot -> TH50 (37 Ohm) ->
MLU+ <- L50 <- C50, C51, C53, C54 (200 WV) <- D1 cathode, TR1 drain
MLU- <- C52, C?? <- D2 anode TR2 source (by way of ferrite bead & 1T primary of T3
Active Board (MLU Rectifier Board)
Has D1, D2, TR1, TR2, T3, PL1 (fan )
Primary of T1 main high frequency transformer
Connected to Active Board
Secondary of T1.
Provisioin for 7 outputs, on my version T1 only has 4 outputs, one very high current & three lower current outputs.
|The input protection fuse
can be seen next to the fan. It tests good, so
there's some other problem.
The fan runs on 12 VDC.
Next remove all the output modules.
On the bottom of the power supply there are a 5 pairs of screws, 3 pairs are for the narrow modules and 2 pair for the double width module.
On the back there is a insulating paper held by a plastic fastener which when squeezed easily comes out exposing the input connecting screws shown below.
To remove the input module from the sheet metal chassis you need to use a real Philips #1 screwdriver (a nut driver has too big a shaft to get past power supply parts.
|Input Wiring Table
This is for the Opto Isolated mains failed & Inhibit options.
thinking of using external power supplies (+5, and two
floating 12V) for power, thus bypassing the the dead
supply module. Another option would be to use an
external source of an H.F. signal (what frequency?) to
drive the output transformer.
page created Nov 16 2011.