Operating instructions

LOCAL OPERATION
3-20
The Audio frequency input connection to the transmitter must be to the audio input, in place of the
usual microphone input. This connection will vary for differing types of equipment. Points to
note are:-
• The microphone must be disconnected, as any input from it would affect the performance of
the test.
• The microphone and its cable may complete the ‘keying’ circuit of the transmitter using a
‘press to talk’ switch, in which case an alternative arrangement must be provided.
• The RF output connection from the transmitter should be made using good quality RF cable
with correctly fitted connectors. Worn connectors and damaged or kinked cable can give rise
to high levels of reflected power. This can cause misleading results and possible damage to
the transmitter.
• Consider the power output of the transmitter and connect to the appropriate input connector
on the monitor. The maximum power to the BNC (Antenna) socket is 1 W and to the
‘N-Type’ connector 150 W. If the transmitter output power exceeds this level then a suitable
power attenuator should be connected between the transmitter and the monitor or a calibrated
‘sniffer’ used to take a sample of the output, using a dummy load if necessary.
• The power source for the transmitter should be reliable and stable. The battery of a vehicle
may discharge if supplying a transmitter during prolonged testing or the ‘earth’ common
return connection may become open circuit if the transmitter is removed from its normal
location.
The procedure for making each of the tests listed above follows. Some of the tests may require
separate operations and others will only require a reading to be made.
Hot surfaces
Take care when touching the RF Input Type N connector after the application of
high levels of continuous power. If 50 W is exceeded for a prolonged period, the
temperature of the connector can become excessive.
Setting up
When all the required connections have been made, select the Tx TEST mode to display the screen
and menu show in fold out diagram (2-0).
Set the parameters or options to suit the test requirements, from the
TRANSMITTER TEST menus.
The complete setup can be stored by making use of the internal setup/results memories or the
optional memory card facility. Both of these features are described under Stores, settings/results,
later in this chapter, starting on page 3-91.
RF generator state
This Service Monitor is a duplex instrument as mentioned earlier. (See Using the test modes, on
page 3-16.) The state of the RF generator is shown on the TX TEST display by the legend
RF GEN ON or RF GEN OFF. The state of the RF generator can be switched by pressing the top
left soft key.
Tx frequency
Press the [Tx Freq] key.
The soft key options change to those shown in fold out diagram (2-1).
The receiver circuits of the Service Monitor must be set to the RF output frequency of the
transmitter under test. This can be set manually using the data input keys, or automatically by
pressing the [Auto Tune] key.
WARNING