Operating instructions

TECHNICAL DESCRIPTION
4-7
Tx test mode
When operating in the Tx TEST mode the Service Monitor has to provide a source of modulation
for the transmitter being tested, and also analyze the RF output signal from the transmitter.
Modulation sources
The modulating signal is provided by one or both of the audio generators or the data generator and
is taken from the AF GEN OUT connector on the front panel.
PROGRAMM-
ABLE
ARRAY
PROGRAMM-
ABLE
ARRAY
LOOK-UP
TABLES
EPROM
LOOK-UP
TABLES
EPROM
A.F. OUTPUT
DRIVER
MODULATION
DRIVER
LOOK AND LISTEN
SWEEP DRIVER
DATA
GENERATOR
(AF GEN. 2
ONLY)
AF GEN 2
WAVEFORM
SHAPE
DATA
TO A.F.
O/P ON
FRONT
PANEL
TO R.F.
GEN.
MOD.
CONTROL
TO 90 MHz
VOLTAGE
CON-
TROLLED
OSC.
AF GEN 1
WAVEFORM
SHAPE
DATA
AF GEN 2
OUTPUT
LEVEL
DATA
AF GEN 2
FREQ.
DATA
AF GEN 1
OUTPUT
LEVEL
DATA
AF GEN 1
FREQ.
DATA
D
A
D
A
D
A
D
A
A
A
A
B
B
B
C
C1412
Fig. 4-3 AF generators, detailed block diagram
Audio generators
The Service Monitor has two AF generators, shown as ‘AF generators’ on the simplified block
diagram. A detailed block diagram of the AF generators is given in Fig 4-3. These are used as
modulation sources for the Tx, Rx and Dx TEST modes and as audio test signal generators in the
AF TEST mode. They have a frequency range of 20 Hz to 20 kHz and the output waveform of
either generator can be sine wave or square wave. Both generators are of similar design, with
minor variations. The generator designated ‘GEN 2’ is also used for other functions which do not
conflict with its functions as an audio generator. These uses will be mentioned where relevant.
Each of the circuits function in the following manner:-