Sea Tel DAC-03, Installation And Operation Manual

Page: 33 / 80

DAC-03 Tracking Antenna Controller Installation
4-3
band selected in the MODE – TRACKING display.
•
Tone generators are used to provide a 22 kHz tone, tone ON when hi band is desired and tone OFF
selects low band. The tone generators are commonly used to provide band control of an Americas
LNB.
•
Coax switches might be used to select which signals are to be routed to the matrix switch.
AGC & GND - External AGC, or Modem Lock, input .
•
External AGC input must be 0 to 5 Volts DC analog signal, positive going voltage proportional to
satellite signal input level and must be real-time in its response to antenna pointing.
•
External Modem Lock from a satellite modem is used as a positive ID that the antenna is on the
desired satellite.
This input is NOT used for Tracking purposes , it is only used for satellite
identification to acquire the correct satellite during search. To enable the external modem input
you must include a 2 in the SYSTEM TYPE parameter (If your system type is presently 76 or 77,
then change it to 78 or 79) and
NID MUST be set to 0000 .
•
Connections - The modem lock signal connects to EXT AGC and a ground reference from the
modem connects to GND. The expected signal from the modem is 0VDC to +5VDC. Low voltage
indicates modem lock, high voltage indicates modem unlock.
NOTE - If the modem signal produces a
negative voltage, an external diode will
need to be installed across the modem
signal and ground (Cathode to modem
signal, Anode to ground). Voltages up to
+/- 15 VDC can be used with addition of a
resistor voltage divider to supply 0-5VDC
into the ACU . An example of external
components is show here.
•
Testing - The input connections from the modem can be tested by selecting the external AGC
input and monitoring the displayed value. To select external AGC, set the tuning frequency to
0000. Normally, AGC readings below 2048 are considered a low condition and indicate modem
lock and AGC readings above 2048 are considered a high condition and indicate modem unlock.
[If
you find the AGC reading for locked and unlocked conditions to be reversed you must add 128 to
your current SYSTEM TYPE parameter]
. Turn tracking OFF when checking the external AGC inputs.
Be sure to properly retune the receiver frequency when you are finished testing the external input.
•
Operation
- In NORMAL operation, AGC must be above Threshold AND external MODEM Lock
input must be locked to Track the satellite. If you are tracking a satellite signal and the AGC is
above threshold (Tracking light on solid) but the external AGC signal rises above 2.5 volts for more
than 20 seconds (external MODEM input
UNLOCKED ) the ACU will automatically retarget the
selected satellite.
TB-3 Step-By-Step (SBS) Gyrocompass Input . Use the COM, A, B and C screw terminals to connect
the SBS Gyrocompass to the ACU. Some SBS Gyro distribution boxes have terminals which are labeled S1,
S2 & S3 instead of A, B and C.
TB-4 NMEA 9-pin PCB
.
•
TX+ and TX- screw terminals are used to provide GPS NMEA
GPGGA output to a Satellite Modem used with Sea Tel
Transmit/Receive (TX/RX) antennas.
•
RX+ and RX- screw terminals are commonly used to connect
GPS (Latitude and Longitude) or Gyro Compass (Heading) NMEA
inputs to the ACU J-13 communications port.
•
+24V and GND screw terminals are commonly used to provide
+24 VDC operating voltage to a GPS, Dual Antenna Arbitrator or
other below decks tone generators or switches.