Before measurements, we need to connect GPS/BDS receiver in the instrument with external GPS/BDS antenna and feeder cable to synchronize GPS/BDS signal. In order to rapidly trace the GPS/BDS signal, these cables should be erected correctly. Only when the entire process including searching GPS/BDS signal, fixing, tracking, and disciplining Rubidium oscillator is over, can it start to perform the measurements.
1. How to Erect GPS/BDS Antenna?
The position to erect the GPS/BDS antenna is quite different under different environment.
The GPS/BDS antenna should be erected in the open air without obstacles like tall buildings, trees, trucks, etc. When erecting GPS/BDS antenna, it should have a wide angle of more than 120° sight to sky, as shown in Fig 1.
Fig1 Common Requirement to Erect GPS/BDS Antenna
GPS/BDS antenna should be erected under lightning rod cover （incline at 45° from the lightning rod）and kept horizontal distance with lightning rod for more than 2 meters, as shown in Fig 7-2.
Fig2 Requirement to Erect GPS/BDS Antenna
To erect multiple GPS/BDS antenna, the horizontal interval must be more than 0.5 meters between each antenna.
The GPS/BDS antenna receiver should be erected vertically, to make sure that the receiving end is parallel to the ground.
2. GPS/BDS Antenna Should Be Kept Distance With Areas As Below
• Area under high tension power line;
• High radiation area of TV tower;
• Near radiation area of RF antenna main valve in base station;
• Radiation area of microwave antenna;
• Other same frequency interference or high magnetic field interference areas;
• Area closed to wall (must keep 1-2 meters space).
3. Special Attention When Erecting GPS/BDS Antenna
• Keep distance from high tension power line, power supply cables, and telephone lines;
• If the feeder cable is too long, it should be straightened instead of being coiled up in order to avoid signal loss caused by electromagnetic field;
• The feeder cable cannot be stressed or compressed; and the joints should not be deliberately bent or pulled in and out by force to avoid damage;
4. Erecting Requirements Inside Building
• The GPS/BDS antenna should outstretch from the window of the building through the provided bracket; Erecting the cable from highest floor according to the cable length, and fix the bracket with bandage;
• Erecting GPS/BDS antenna at one wall if possible, instead of at the corner of the floor;
• Erecting long GPS/BDS antenna if there are tall buildings all around, to ensure that it can receive sufficient GPS/BDS signals;
5. Erecting Requirements On The Roof
• Erecting GPS/BDS antenna in the middle of the roof, instead of at low wall around the roof;
• It is not allowed to erect GPS/BDS antenna at the corner of the roof because it is most vulnerable to lightning;
• GPS/BDS antenna should be kept away from the small appendages on the roof;
6. Erecting Requirements By The Side Of Tower
• Erect GPS/BDS antenna on the top of the station room by the side of tower or outside the station, and keep away from the following area:
• Any position in the tower;
• Wiring frame between the tower and the station room;
7. Special Notes
• When there is no satellite signal found in the searching process or the number of satellite signals found is less than 4, please move the GPS/BDS antenna and erect it in an open area if possible;
• Observe the satellite-searching process on the instrument and see if it can get stable signals of 4+ satellites; if there are many satellites found but the signals are not stable, the instrument cannot synchronize to the satellites; or it re-starts to search, position, synchronize to satellites under oscillator disciplining process, the instrument will not get into the state for measurements.