M7/M7L/M7LT Modular Satellite Modem Maintenance
M7/M7L/M7LT - Rev. 0.05 3-109
3.11. Special Control Mechanisms
The modem includes several special controls that were built in for specific customer systems, but are
available in the standard modem. These are not considered normal operation so care must be taken
if they are used.
Power-Up Behavior
Analog Monitor Output
RTS Monitor
3.11.1. Power-Up Behavior
The modem can be set to always revert to the transmit carrier disabled on power-up. This might be
useful for example in mobile environments where the antenna may not be deployed or aligned on
each power-up cycle. Setting this option in the <Mod: IF - Mute> parameter to “Manual & Power
Loss“ allows such operation.
In other cases the user may require that the modem always revert to a specific configuration on
power-up. The normal behavior is for the modem to power-up with the last settings still in effect. One
of the options in the Unit Configuration column is <Unit: Config – Power-Up>. The default setting is
“Last” which performs as the normal described above. A user can select any of the stored
configurations to be recalled on each power-up cycle. This could be useful in a mobile environment or
a DAMA system where a control channel is desired on each power-up. In a large system, units can
be pre-set to a specific configuration during initial commissioning, but then easily changed to another
configuration for normal operation.
3.11.2. Analog Monitor Output Operation
The modem has a built-in function to output an analog voltage representing the current value of one
of three internal parameters by setting the <Unit: Monitor - Mode> parameter. The available
parameters that can be selected for this output are:
Receive carrier level (Dmd CXR Level)
Receive Eb/No (Dmd Eb/No)
Transmit output power level (Mod CXR Level)
The analog output can be tailored to the user requirements through any of the control interfaces. The
output the processor allows control of the full scale voltage by setting the <Unit: Monitor – Full>
parameter to a range of +1.0 Volts to +10.0 Volts and the slope by setting the <Unit: Monitor –
Output Slope> parameter to positive or negative. These two settings control the output slope (gain
and direction) of this analog output voltage.
To illustrate consider the example of using the Receive carrier level for the monitor output to
automatic antenna positioning equipment. For this example, the modem has a carrier input range of
–20 to –60 dBm.
If the antenna auto-track controller requires a positive slope between 0 and +10 Volts, where +10
Volts represents the maximum received signal level, set the <Unit: Monitor – Full> parameter to
“+10.0” and the <Unit: Monitor – Output Slope> parameter to “Negative”. These settings have the
effect of inverting the slope of the AGC signal and setting the gain of the voltage to match the input to
the antenna controller.
NOTE: The output voltage is always a positive voltage.
The analog output presented at pints 5 (+voltage) and 6 (gnd) on the rear panel Alarms connector
(J6). The voltage pin has a1kΩ output impedance, protecting the driver circuitry from shorts.
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