Operating instructions

LOCAL OPERATION
3-16
Using the test modes
Brief descriptions
As the Service Monitor 2948 is a duplex instrument, the RF signal generator and the receiver
circuits are able to operate simultaneously. This allows mobile transceivers to be tested under
their normal operating conditions, with both their receiver section and transmitter section
functioning. By selecting a particular test mode on the Service Monitor, one or both sections of
the transceiver can be studied. A brief description of the function of each test mode is given
below. Detailed user instructions follow under the relevant headings.
Tx TEST
With Tx TEST selected, the TRANSMITTER TEST screen is displayed and access to all Tx
TEST mode features is available. See fold out diagram (2-0) at the end of this chapter.
The AF voltmeter makes measurements to the signals from the Service Monitor demodulator and
displays the results.
The RF signal generator is active, producing an RF signal at the frequency and level set in the
Rx TEST mode. This signal will be modulated at the level and frequency set, if the modulation
generator selection does not conflict with the requirements of the Rx TEST mode.
Rx TEST
With Rx TEST mode selected, the RECEIVER TEST screen is displayed and access to all Rx
TEST mode features is available. See fold out diagram (3-0) at the end of this chapter.
The AF voltmeter makes measurements to the signal obtained from the demodulated output of the
mobile transceiver and fed into the AF INPUT socket on the front panel of the Service Monitor.
The AF generators are active at the frequencies and levels set in the Tx TEST mode and their
output routed to the AF GEN OUT socket on the front panel of the Service Monitor. The AF
generator selection can conflict with the requirements of the Tx TEST mode.
Dx TEST
With Dx TEST selected, the DUPLEX TEST screen is displayed and access to transmitter and
receiver test features is available. See fold out diagram (4-0) at the end of this chapter. These
features are not as comprehensive as those available from the TRANSMITTER TEST or
RECEIVER TEST screens, but do allow measurements to be made to the major parameters. The
Service Monitor has two AF generators, either or both of which can be used to modulate the
transmitter being tested or the RF generator. However, each generator can only serve one function
at the same time. There is only one AF measurement path, which is switched by the software
between receiver test and transmitter test functions.
SPEC ANA
With SPEC ANA selected, the
SPECTRUM ANALYZER screen is displayed and access to the
spectrum analyzer features is available. See fold out diagram (6-0) at the end of this chapter. The
RF signal generator is active, producing an RF signal at the frequency and level set in the
Rx TEST mode, if the tracking generator feature is not selected. The spectrum analyzer tracking
generator signal is provided by the RF generator.
The modulation generators will modulate the RF signal generator, with the same provisos as in Rx
TEST mode. If the LOOK AND LISTEN screen is displayed, AF Gen 2 is used to provide the
sweep signal, therefore it is not available to provide modulation.