COBHAM SEA TEL 9711IMA-70, Installation Manual

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9711IMA-70 Setup – Blockage & RF Radiation Hazard Zones
8-1
8. Setup – Blockage & RF Radiation Hazard Zones
The Blockage Zones function inhibits the antenna from transmitting within certain pre-set zones. This is typically some
structure of the ship that prevents satellite signal from getting to the Sea Tel antenna when the ship is at headings that put
that structure in-between the satellite and the satellite antenna,
However, it can also be used as an RF Radiation Hazard zone. If there is an area where people may be near the antenna
(within 2 meters), in the antennas transmitted beam for extended periods of time the zone can be set up so that transmit
from the satellite antenna will be disabled whenever the antenna is pointed in that zone.
8.1. Radiation Hazard and Blockage Mapping
The MXP can be programmed with relative azimuth sectors (zones) where blockage exists or where transmit power
would endanger personnel who are frequently in that area. Your MXP software allows you to set four zones.
When you create these
ZONES (up to four), several things happen when the antenna is within any one of the
zones:
1. Tracking continues as long as the AGC value is greater than the Threshold value. When the AGC value
drops below Threshold, the antenna will wait “Search Delay” parameter amount of time and then re-
target the satellite you targeted last. Timeout and re-target will continue until the satellite is re-acquired
and tracking can resume.
2. The satellite modem transmission will be disabled until the antenna exits the zone.
The lower and upper azimuth limits are entered into the REL
start, REL stop and EL fields within the MXP for each of the
blockage zones you wish to create (up to four). Each zone can
also be given a name (ie Mast, Deckhouse or Stack:
REL Start is the Lower Relative AZ limit (this is the
more counter-clockwise of the two points, even if it
is numerically larger). REL Stop is the Upper
Relative AZ limit (the more clockwise of the two
points) for pattern mapping of each. Enter the
elevation value that represents the top of the
blockage between the two azimuth limit points in the
EL field.
Repeat for up to four zones, click SAVE when
completed.
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.
EXAMPLE - Overlaid Blockage Zones:
A ship has a Sea Tel antenna mounted on the center line of the ship.
A mast mounted on top of a deckhouse (like the picture above) is forward and an engine exhaust stack, also on a
deckhouse, is aft. These two blockage areas have wide azimuth blockage at lower elevations and then a narrower
azimuth area of blockage extends up to a higher value of elevation.
EAR Controlled - ECCN EAR99