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Interfacing iDirect
Interfacing an iDirect Modem to the RC1500B Tracking
Antenna Controller
iDirect modems can produce an analog voltage suitable for the AGC of an ACU
to track an inclined orbit satellite. To enable the voltage output on the iDirect
modem, set "tx_handshake_enabled = 1" in the modem options file. The modem
console port is an RJ45 receptacle on the back panel of the modem.
Here are the connections between the modem and the ACU.
Modem RJ-45 Console
Port Terminal
Console Port RJ45-4
Console Port RJ45-8
AGC Configuration
The AGC has two analog input channels. In this case, it is recommended to use
AGC2. Each AGC channel has a gain and offset potentiometer adjustment
accessible via openings in the back panel. Details on adjusting the gain and
offset can be found in the AGC Tuning section starting on page 22.
The AGC2 Gain and Offset pots should be adjusted so that when 0 volts is
presented to the controller, on the AGC2, the displayed signal strength value is
approximately 0 and when 5 volts is input on AGC2 the displayed signal strength
reading is around 950. The displayed signal strength value should vary as the
input voltage changes from 0 to 5 volts.
The ACU maintains user defined 'AGC Threshold' items found in the CONFIG
menu. When the AGC input signal strength value is greater than this value, the
ACU assumes that a satellite signal is present and antenna peaking can occur.
When the AGC2 Gain and Offset pots are configured as specified above, an
appropriate value for the AGC Threshold is '500'. A signal strength value of 500
corresponds to an analog input voltage of approximately 2.5 volts. When the
signal strength input level is above 2.5 volts the modem is locked and peaking
can occur.
ACU Terminal
ACU AGC RTN, J1-3
(ACU Chassis Potential)
ACU AGC 2, J1-2
Table 4 – iDirect Modem Connections
33
Description
Analog return
The analog voltage varies with received
signal strength (RSS).
The voltage is 0 to 2.5 volts when modem
is unlocked and 2.6 to 5 volts when modem
is locked.
RC1500B Quick Start Guide
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