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Maintenance
M7/M7L/M7LT Modular Satellite Modem
4-16
M7/M7L/M7LT - Rev. 0.05
placed closer than the required receive acquisition range. Using this scheme requires the use of the
demodulator search mode.
Intelsat in the latest IESS 308/309 has changed the definition of the C0 and C1 values. This option
allows compatibility with any definition.
4.7.1.2.9.
How do I determine the transmitted "Symbol Rate" of the modem?
This particular parameter used to be a lot simpler to define. With the introduction of Turbo
Product Codes coupled with all the other modem modes and options like programmable IBS
multiplexer data load it is now extremely hard to define. The modem knows though, and it is
available at the front panel parameter showing the current transmit/receive symbol rate. It is
in the
<Mod: Test
– Symbol Rate>
and the
<Dem: Test
– Symbol Rate>
parameters.
4.7.2.
Why does It do that?
4.7.2.1.
The modem is operating fine and then suddenly will not lock!
You probably have the differential encoder/decoder turned off. It is only provided as a control for very
special cases and should normally be set to “Enabled”.
4.7.2.2.
The modem changed its operating parameters without me doing anything!
The ACR or Automatic Configuration Recovery feature is possibly enabled by setting one of the
<Unit: Config
– Recall X>
parameters set to a non-zero value. This will change the modem
configuration if the receive carrier is lost longer than the number of seconds entered.
The
<Unit: Config
– Power-Up>
parameter may be set to change to a specified configuration on
power-
up. The normal setting for this is “Last” (0).
4.7.3.
Front Panel Control
4.7.3.1.
What happened to the “Differential Encoder/Decoder parameter?
In normal operation there is no need to disable the Differential encoder or decoder. We only found
that occasionally someone disabled it and then had problems locking up to carriers, so this capability
was initially removed from front panel control. All of the latest firmware however now allows this
control, so you may need to update your firmware.
4.7.3.2.
How do I enter a number with a minus sign?
At any time during the “Edit” process the “+/-“ key will change the sign of the current entry (if the
change is possible). In the quick edit mode this can be the first key pressed, so for instance, if the
current setting for modulator transmit output level is
–10 dBm then pressing “+/-, 12” will enter a value
of
–12 dBm. You could also press “1+/-2” or “12+/-” with the same result.
4.7.3.3.
Why doesn’t the M7 front panel act like the PSM-2100 or PSM-4900? [and] How do I
make it act like the PSM-2100?
The M7 has many more features and programmable options than the PSM-2100 modems. A close
match is achieve
d by disabling the “quick” entry mode and remembering to press the “Edit” key first
instead of the “Enter” key. Once you become accustomed to the “Quick” entry mode and using the
change sign (+/-) and decimal point keys you will find it more convenient than any entry on the PSM-
2100.
4.7.3.4.
Why does the transmit carrier turn off whenever I make a change?
First the transmit carrier can be set to a mode which will turn the carrier off if any change is made that
would result in a possible interference with other carriers on the satellite. This mode can be set to one
of three states: Automatic, Confirm or Manual. Automatic will turn the carrier off during the parameter
change and return the carrier on (if currently enabled) after the change is completed, Confirm will ask
if the carrier should be left on (requiring a “yes” or “no” answer), while Manual will always turn the
carrier off after a change. This option is set in
<Mod: IF
– Mute>
. More directly the setting described
is probably set to “Manual” mute mode.
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