Maintenance Guide Part 1

NeTIS MAINTENANCE GUIDE – Version 1.1 26/139
come from a disturbance or an incorrect adjustment of a duplexer or an incorrect
separation of the transmission and receiver antennas; to refine the diagnosis stop the
BS transmission by disconnecting the CPU from the PA.
Checking a DCTR circuit
Connect an RF generator to the DCTR input to be tested, adjusted to the programmed nominal
receiver frequency on the BS; the RSSI level indications should correspond within 3 dB to the
test generator level within the range of - 20 to - 90 dBm. Further, the D1 LED of the DCTR
module lights progressively as the generator level exceeds - 70 dBm. Several faults can be
detected at this level:
The viewed RSSI level is weak and almost constant whatever the generator level;
check the programmed receiver channel, check that the DCTR module is compatible
with the frequency band, find out if it is responding on a neighbouring carrier; check
the DCTR module
The viewed RSSI level varies correctly either at a weak level (- 90 to - 50 dBm), or at
a strong level (- 50 to - 20 dBm) but not over the entire range: the DCTR module is
defective
The viewed RSSI level varies correctly at a weak level but varies at levels greater than
- 40 dBm and the D1 LED does not light, the DCTR module is defective
The viewed RSSI level varies correctly at a strong level but not at a weak level
although the noise levels are correct: the DCTR module is probably defective, it
should be checked
2.6.7 C ONFLICTS BETWEEN NMT ALARMS AND LED OF BS
If there are different alarms on NMT for the same base station concerning VSWR, PA or Tx
and the LEDs on the base station do not correspond to this, that’s means that there is an issue
with the power alimentation of each board. In this case, the LED (+30v) on the supply board
is very weak or off.
1 – switch off the base station
2 – disconnect on the PA board (rear of the rack), supply cable (2 pins, green connector)
3 – disconnect the alarm connector (SubD 15pins)
4 – start the base station
If the LED +30v is ok, exchange the PA module
If the LED is still not working, exchange the main supply board
If both are not ok, check the different wire of supply