SRCU/SOCU board with GPS/GLONASS module can trace both of the satellite systems.
You can check the number of satellites that can be traced by any satellite system. But the problem is that we are not sure whether our BITS system is locked with GPS system or GLONASS system and which system is better to be locked GPS or GLONASS.
Following procedure can be used to lock the BITS system with GPS and it assumes that the GPS/GLONASS card is installed on SRCU1 board.
1.In the boards monitoring interface of NMS, select SRCU1 board, and then right click SRCU1 board and select Query/Set Work Parameter of GPS/GLONASS Card.
2.Set the work mode as GPS.
3.In the boards monitoring interface of NMS, select SRCU2 board, and then right click SRCU2 and select Query/Set Work Parameter of GPS/GLONASS Card. Set the work mode as GPS.
4.Set the satellite signal of SRCU1 (i.e., CSSR1) as active reference source of the system.
5.In the data configuration interface of NMS, select SRCU1 board, double clock SRCU1 and bring out the SRCU1 configuration window. Select Y for Test Satellite Signal 1 and Test Satellite Signal 2. Load the board.
6.After 24 hours, watch the test result on the FREQ query of NMS. The tested value of CSSR2 on the time of 86400s (1 day) should be 1E-11 or less.
Same procedure can be used to set the work mode of SOCU board to GPS.
Navigation Satellite Timing and Ranging (NAVSTAR) GPS refers to a high-precision global satellite positioning system deployed by US Navy Observatory. It is a 24 hour satellite navigation system that can obtain high precision information on position, velocity and time. GPS provides the 3D positioning information with the accuracy of 10 yards (about 9.1m) and the timing signal with the accuracy less than 100ns. The received signal can work as the master reference after processing.
Global Navigation Satellite System (GLONASS) is controlled and maintained by Russia. GLONASS consists of 24 satellites, and 5 to 11 satellites are visible from any point on the earth. GLONASS accesses satellites in multi frequencies, thus the whole system works like a frequency division multiplexing access (FDMA) system.
The output specifications of the system in locked mode keep unchanged no matter GPS/GLONASS or GPS is used. However, GLONASS has less satellites than GPS, and the GLONASS satellite signal may be absent for a period of time, during which, the system shall enter the holdover. Therefore, if GLONASS is used, the holdover specifications should be high enough. Generally, the Rubidium oscillator should be used as the local oscillator.
This means that for SRCU/SOCU board active tracing source should be GPS not GLONASS.
Using above procedure we can lock the BITS system to GPS. Take care while commissioning the system whether you have selected the GPS as work mode.