System information

Setup 9797B-70 C-Band TXRX
5-6
CAUTION: The Lower Relative AZ limit is the more counter-clockwise of
the two points (even if it is numerically larger) and the Upper Relative AZ
limit is the more clockwise of the two points. If you enter the two relative
points incorrectly, Tracking and Searching will be adversely affected.
The ACU provides a contact closure to ground on the SW2 terminal of the Terminal Mounting Strip when the
antenna is pointed within any one of the blockage/hazard zones or the system is searching, targeting,
unwrapping or is mis-pointed by 0.5 degrees or more (FCC TX Mute function for Transmit/Receive systems
only). The contact closure is a transistor switch with a current sinking capability of 0.5 Amp. Pressing the 5
key when the TRACKING window is selected can simulate a manual BLOCKED condition to test SW2 logic
output. UP arrow key is pressed to turn the simulated blocked condition OFF.
When used as simple “BLOCKED” logic output for a single Sea Tel antenna, this output could be used to light
a remote LED and/or sound a buzzer to alert someone that the antenna is blocked, and therefore signal is lost.
In a “Dual Antenna” installation, this logic output(s) is used to control Dual Antenna Arbitrator panel of coax
switch (or switches) to switch the source inputs to the matrix switch from Antenna “A” to Antenna “B”, and
vice versa.
When used as simple “RF Radiation Hazard” logic output for a single Sea Tel TXRX antenna, this output
could be used to suppress RF transmissions while the antenna is pointed where people would be harmed by
the transmitted microwave RF power output. The SW2 output would be interfaced to the satellite modem to
disable the TX output signal from the Satellite TXRX Modem whenever the antenna is within the RF
Radiation Hazard zone(s).
When used for “FCC TX Mute” logic output for a single Sea Tel TXRX antenna, this output is used to
suppress RF transmissions whenever the antenna is mis-pointed 0.5 degrees or more, is blocked, searching,
targeting or unwrapping. The SW2 output would be interfaced to the satellite modem to disable/mute the
TX output signal from the Satellite TXRX Modem. When the mute condition is due to antenna mis-pointing, it
will not un-mute until the pointing error of the antenna is within 0.2 degrees. The default output is contact
closure to ground when the antenna is mis-pointed, therefore provides a ground to “Mute” the satellite
modem from the SW2 terminal of the Terminal Mounting Strip. If your satellite modem requires an open to
“Mute”, refer to SYSTEM TYPE parameter 16 value to reverse the output logic from the ACU.
Programming instructions:
Determine the Relative AZ positions where blockage, or RF Radiation Hazard, exists. This may be done by
monitoring the received signal level and the REL display readings while the ship turns or by graphing the
expected blockage pattern. Elevation of the antenna in normal use also must be taken into consideration. A
Mast or other structure may cause blockage at low elevation angles, but may not cause blockage when the
antenna is at higher elevation angles where it is able to look over the structure. Up to four zones may be
mapped. Only zones which are needed should be mapped (in AZ LIMIT pairs).
In unlimited antenna systems the Relative position of the antenna must have been calibrated by properly
setting the Home Flag Offset (HFO) value in the PCU. The HFO calibrates Relative to display 0000 when the
antenna is pointed in-line with the bow of the boat/ship (parallel to the bow).
Convert the relative readings to AZ LIMIT/EL LIMIT values by multiplying by 10. Enter the beginning of the
first blockage region as AZ LIMIT 1 and the end of the region (clockwise direction from AZ LIMIT 1) as AZ
LIMIT 2 parameters in the ACU. If needed, repeat setting AZ LIMIT 3 & 4 for a second ZONE and then AZ
LIMIT 5 & 6 if a third ZONE is needed. All unneeded zone AZ LIMIT pairs must be set to 0000. Set the
upper elevation limit of each blockage zone (also entered in degrees multiplied by 10).