Operating instructions

4-1
Chapter 4
TECHNICAL DESCRIPTION
Contents
Overview........................................................................................................................................ 4-1
Power supply .......................................................................................................................... 4-2
The display.............................................................................................................................. 4-3
Tx test mode................................................................................................................................... 4-7
Modulation sources................................................................................................................. 4-7
Receiver circuits ..................................................................................................................... 4-9
IF circuits .............................................................................................................................. 4-10
Demodulators........................................................................................................................ 4-11
RF counter ............................................................................................................................4-12
Measurement ranging circuits............................................................................................... 4-12
Distortion/SINAD filter ........................................................................................................ 4-12
Oscilloscope function ...........................................................................................................4-12
Rx test mode ................................................................................................................................ 4-13
RF oscillator................................................................................................................................. 4-13
Modulators............................................................................................................................ 4-15
RF amplifier.......................................................................................................................... 4-15
Audio generators................................................................................................................... 4-15
Modulation control ............................................................................................................... 4-15
Pre-emphasis filter ................................................................................................................ 4-15
AF measuring circuits...........................................................................................................4-15
Oscilloscope function ...........................................................................................................4-16
Dx test mode ................................................................................................................................ 4-16
Spectrum analyzer mode.............................................................................................................. 4-16
Look and Listen function...................................................................................................... 4-16
AF test mode................................................................................................................................ 4-16
Systems mode .............................................................................................................................. 4-17
List of figures
Fig. 4-1 Block diagram of power supply module. ........................................................................ 4-2
Fig. 4-2 Simplified block diagram ................................................................................................ 4-5
Fig. 4-3 AF generators, detailed block diagram............................................................................ 4-7
Fig. 4-4 Input switching and broad band power meter block diagram ......................................... 4-9
Fig. 4-5 RF oscillator block diagram .......................................................................................... 4-14
Overview
This simple description is provided to give the user an insight into the working of the Service
Monitor at the block diagram level. See Fig. 4-2, Simplified block diagram. A detailed technical
description will be found in the maintenance manual relating to this Service Monitor.
The Service Monitor is of modular construction, comprising a number of printed circuit boards, (at
least 15, depending on options included). These are housed in two sub-assemblies, along with
input and output attenuators, power supply, front panel, rear panel and display unit modules. The
Service Monitor is microprocessor controlled and software driven.
The power supply and display unit are described first. The functional circuit blocks of each test
mode are then described in sequence.