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7-2 MICROWAVE SYSTEM A/T
Microwave A/T comprises of - Local A/T of all stations, and Repeaters.
- Hop Test.
- Through Test.
7-2.1 Local A/T:-
There are several makes of Narrow / Wide band microwave systems, near
about all test are same except power supply points, access points. Here for example
Satara M/W station to T.E. end link of 11 GHz (1+ 1) digital M/W system Make-
HFCL, is described.
1. Check of power supply:-
Measure voltage at Battery point and Bay input, note down the voltage drop. Limit :- 1.0
V. If not within limit then measure voltages step by step that is from battery- OCB
distribution- Equipment room distribution-Suit distribution and find out in which section
it is more.
Check the gauges of wires and loose connections.
Output voltages:- some systems are not having access points to measure the output
voltages.
a. Modem shelf PSU
+5.2 V, +3.3 V and -5.2V
Limit: - ±0.25V ±0.15V and ±0.25V
b. RSA shelf PSU
+5.3V +12.0V -5.5V
Limit: - ±0.25V ±0.5V ±0.25V
2. Test on Transmitter:-
- TLO: - Write down the assigned frequency of TLO and measure by Microwave
frequency counter at TLO Mon,
- Press impedance 50ohms, resolution, KHz
- Press offset and get deviation which should be within the limit of ±20 PPM
E.g. Assigned TLO frequencies 11295 MHz
Measured ------“-------------11294.935.207MHz
Deviation ----------------- -5.7PPM
Here 647993 Hz frequency is less than the assigned frequency and deviation is -5.73, so
in PPM it is how much?
PPM =
Out Hz = 64793 = 5.73 PPM
Assigned frequency in MHz 11295
-TLO O/P level (Mon):- Measure output power by spectrum analyzer by tuning TLO
frequency or by Power meter. Limit: - ≥-12 dBm
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