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QMultiFlex-400™ Installation and Operating Handbook
6.2.24.2 Round-trip Delay
The modem needs to know the delay to the satellite in order for Paired Carrier to work. The
following table shows the supported methods of delay entry.
Set location
The modem automatically calculates the satellite round trip delay using
the decimal latitude / longitude coordinates that are entered for the
modem location and the satellite longitude.
Set delay
This mode uses user-entered minimum and maximum satellite round-trip
delay times and searches for the actual satellite delay between the limits.
The size of the delay window directly affects the carrier acquisition time
and should be reduced to +/-0.5ms around the actual measured satellite
delay (as shown on the Status screen) once this has been established
following Paired Carrier achieving lock.
Use GPS
This mode allows mobile Paired Carrier operation (for example, on ships)
without ever having to change location or satellite delay information for
Paired Carrier. Any change in location will not affect Paired Carrier
operation. A GPS source must be attached to the modem via the
modem's remote serial control port, which will be automatically
configured for RS232 at 4800 baud. The modem polls the serial port
regularly for GPS position information. Two GPS protocols are
supported, namely, GPS Fix Data (GGA) and Geographic position
Latitude/Longitude (GLL). The modem will use whichever is provided. It
uses the GPS information to calculate the minimum and maximum delays
to satellite and updates these if they need to change from their existing
values.
6.2.24.3 Satellite Longitude
Range
-180 Degrees to +180 Degrees; step size: 0.01 Degrees
Description:
The longitudinal position of the satellite. A positive number indicates East
and a minus sign can be used to indicate West. If using the modem front
panel then the Up and Down arrow keys are used for setting '+' and '-',
respectively.
6.2.24.4 Earth Station Longitude
Range
-180 Degrees to +180 Degrees; step size: 0.01 Degrees
Description:
The longitudinal position corresponding to the modem location. A positive
number indicates East and a minus sign can be used to indicate West. If
using the modem front panel then the Up and Down arrow keys are used
for setting '+' and '-', respectively.
Table 6-50 Paired Carrier Round-Trip Delay
Table 6-51 Satellite Longitude
Table 6-52 Earth Station Longitude
6-63
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