Sea Tel 9797B-70 C-Band TX/RX, Installation And Operation Manual

Page: 35 / 110

9797B-70 C-Band TXRX Setup
5-7
EXAMPLE 1 - Three blockage Zones: A ship
has a Sea Tel antenna mounted on the port side and
an Inmarsat antenna mounted on the starboard
side. A mast forward, the Inmarsat antenna to
starboard and an engine exhaust stack aft form the
three zones where satellite signal is blocked (as
shown in the graphic). In this example zone 1 is
caused by the mast, zone 2 is from the Inmarsat
antenna, zone 3 is from the stack and zone 4 is not
needed:
ZONE 1 begins (AZ LIMIT 1) at 12 degrees
Relative and ends (AZ LIMIT 2) at 18
degrees Relative. Multiply these Relative
positions by 10. Enter AZ LIMIT 1 value of
0120 and AZ LIMIT 2 value of 0180. In
this case the mast height only causes
blockage up to an elevation of 50 degrees,
so we set EL LIMIT 12 to 0500. If the
antenna is between these two AZ Limit
points but the elevation is greater than 50
degrees, the antenna will no longer be
blocked.
ZONE 2 begins (AZ LIMIT 3) at 82 degrees Relative and ends (AZ LIMIT 4) at 106 degrees Relative.
Multiply these Relative positions by 10. Enter AZ LIMIT 3 value of 0820 and AZ LIMIT 4 value of
1060. In this case the Inmarsat antenna height only causes blockage up to an elevation of 12
degrees, so we set EL LIMIT 34 to 0120. If the antenna is between these two AZ Limit points but
the elevation is greater than 12 degrees, the antenna will no longer be blocked.
ZONE 3 begins (AZ LIMIT 5) at 156 degrees Relative and ends (AZ LIMIT 6) at 172 degrees Relative.
Multiply these Relative positions by 10. Enter AZ LIMIT 5 value of 1560 and AZ LIMIT 6 value of
1720. In this case the stack antenna height only causes blockage up to an elevation of 36 degrees,
so we set EL LIMIT 56 to 0360. If the antenna is between these two AZ Limit points but the
elevation is greater than 36 degrees, the antenna will no longer be blocked.
ZONE 4 is not needed. Enter AZ LIMIT 7 value of 0000 and AZ LIMIT 8 value of 0000. Set EL LIMIT
78 to 0000. If your ACU software includes 5 volt polarization you will not see these AZ & EL LIMIT
parameters.
EXAMPLE 2 - Three blockage Zones, Dual
Antenna configuration:
A ship has 2 Sea Tel
antennas, “Antenna A” mounted on the port side
and “Antenna B” mounted on the starboard side.
Antenna A is designated as the
master antenna.
The mast forward, Antenna B to starboard and the
engine exhaust stack aft form the three zones
where satellite signal is blocked from Antenna A.
The SW2 logic output from Antenna A (ACU A)
and Antenna B (ACU B) are used to control a “Dual
Antenna Arbitrator” panel of coax switches which
route satellite signal from the
un-blocked
antenna to the inputs of the matrix switch. If
both antennas are tracking the same satellite, they
will not both be blocked at the same time. The
logic output will switch to provide satellite signal
to the below decks equipment from Antenna A
when it is
not blocked
and will switch to provide
satellite signal from Antenna B whenever Antenna
A
is blocked
. The switches will not change state
if
both
antennas are blocked, or if
both
are on
satellite.
Antenna A is the same as the previous example and its ACU would be set to those AZ LIMIT
values.