Operating instructions

LOCAL OPERATION
3-60 46882-311D
To enter the AF TEST mode press the blue [AF TEST] key. This will cause the screen and menu
shown in fold out diagram (7-0) to be displayed.
When the AF TEST mode is selected, the combined output from the AF generators, plus the data
generator facility, is available at the AF output connector. Signals fed to the AF input connector
are routed to the AF signal analysing circuits. See Fig. 3- 17, Audio test setup.
The frequency, level and shape parameters of the audio generators can be set within the following
limits:-
Freq. range 10 Hz to 20 kHz
Level range 0.1 mV to 4 V rms
Shape option Sine or square
By using the AF signal generators and the measuring functions of the Service Monitor, it can be
used for performance testing of passive and active AF circuits such as filters and amplifiers.
Frequency, level, distortion level, SINAD level and signal to noise ratio measurements can be
made. The oscilloscope facility is available to observe and measure waveforms. The tones
receiver facility is available for the performance checking of features such as digitally coded
squelch generators.
The AF output signal and the measuring facilities can each be used independently.
Setting up
The audio generators are the signal sources for AF testing. Good practice is to disable the source
until tests are set up. This is achieved by selecting each of the generators in turn and pressing the
orange [ON/OFF] function key to display
Off adjacent to each of the generator’s output data on the
display. The required generator or generators can be set up in the
Off condition and enabled by
the above procedure when all connections and setting are complete.
To select and set up the audio generators press the[Audio Gen] key. This will display the audio
setup menu shown in fold out diagram (7-2).
Repeated presses of the [Gen1/Gen2] key will highlight the
and legends in turn to
indicate the selected generator.
Set up the audio generator(s) for the required frequency and output level by using the soft keys
and data input keys:-
[Gen 1/Gen 2] to select AF1, then, [FREQ][n]....[n][kHz/Hz]
[LEVEL][n]...[n][V/mV/dBm]
then [Gen 1/Gen 2] to select GEN2 if required,....[.../dBm]
The FREQ [
] and [ ] and the LEVEL [ ] and [ ] keys can be assigned to AF generator
frequency and level. See Incremental adjustments which starts on page 3-62.
The shape of each audio generator output waveform can be either sine or square wave. This is
controlled by first selecting the audio generator as for
On/Off control above, then pressing the
[SHAPE] key to toggle between the options.
Input level measurement
The measured level of signals applied to the AF INPUT connector can be displayed in volts, dBm,
dBV or mW. The selection is made from setup page 2, as described under Audio Level Measured
in: on page 3-12. When the input level is displayed in dBm or mW, the signal is assumed to be
measured across 600 Ω.
The 600 Ω interface unit allows the Service Monitor to provide a 600 Ω termination. (See Audio
Input Impedance on page 3-12.) With the input impedance set at 600 Ω, the indicated level is
that of the input to the Service Monitor. With the input impedance set at
High, the indicated level
is that of the input to the Service Monitor with an assumed 600 Ω load.