Operating instructions

OPERATING MANUAL 2945A
46882-311D 3-65
Observing tones signals in other test modes
The effect of any tones signalling on transmitters or receivers under test can be studied using any
test mode of the Service Monitor.
When a test mode is selected, (either by pressing the [Tx TEST] key, [Rx TEST] key etc. or by
pressing the [Return] key), while any tones signal is running continuously (CTCSS or DCS
Tones
On; Sequential or DTMF continuous mode Sending), the tones will continue to be generated.
See the
Tones ON/OFF control section of each specific tones description.
Signal routeing
The tones sub-mode can be entered from either Tx TEST, Rx TEST, Dx TEST or AF TEST
modes.
The encoded signal produced by the Service Monitor can be routed to the equipment under test in
two ways:
• As a modulated RF signal from either of the RF output connectors.
• As an AF signal from the AF GEN OUT connector.
Similarly, an encoded signal produced by the equipment under test can be routed to the Service
Monitor in two ways:
• As a modulated RF signal to either of the RF input connectors.
• As an AF signal to the AF INPUT connector.
The input and output routeing settings are made from the TONES selection screen. Pressing the
[Tones In] or [Tones Out] key alternates the setting between
and . The selected settings
will be retained until reset, either manually or by recalling instrument settings. Any tone
sequence or continuous tone that is running when an input or output routeing setting is changed
will be stopped.
RF input attenuators
The RF input circuits of the Service Monitor are auto-ranging under most operating conditions.
When operating in some of the tones modes this can be a disadvantage as the tones decoders need
to receive the leading burst of any transmission. Therefore when TONES mode is selected, the
auto-ranging function is disabled and the RF input sensitivity of the service monitor is set
manually.
This is done by using the [
] and [ ] keys on the TONES selection screen. For correct
operation of the TONES decoders, the input signal level should not exceed the level set.
Each keypress will switch the sensitivity of the service monitor up or down by 10 dBm. If the
level of the applied signal is unknown, it can be measured using the Tx TEST mode. The Service
Monitor
RF Input Level can then be set above the measured level.
The following table shows the RF input level settings that are available for either of the RF input
connectors.
RF N in RF Antenna in Audio
398 W 56.0 dBm 1.00 W 30.0 dBm <40.0 V
39.8 W 46.0 dBm 100.0 mW 20.0 dBm <20.0 V
3.98 W 36.0 dBm 10.0 mW 10.0 dBm <10.0 V
398 mW 26.0 dBm 1.00 mW 00.0 dBm <4.0 V
39.8 mW 16.0 dBm 100
µ
W -10.0 dBm <2.0 V
3.98 mW 6.0 dBm 10
µ
W -20.0 dBm <1.0 V
398
µ
W -4.0 dBm 1
µ
W -30.0 dBm <400 mV
40
µ
W -14.0 dBm -40.0 dBm <200 mV
4
µ
W -24.0 dBm -50.0 dBm <100 mV