Sea Tel ST88-21 C/Ku-Band TVRO, Installation And Operation Manual

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ST88-21 C/Ku-Band TVRO Setup – Blockage & RF Radiation Hazard Zones
10-1
10. Setup – Blockage & RF Radiation Hazard Zones
This section discusses how to set up blockage, or RF Radiation Hazard, zones.
10.1. Radiation Hazard and Blockage Mapping (AZ LIMIT parameters)
The ACU 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 ACU software may allow you to set four zones or it
will only three zones and i5 volt polarization.
When the AZ LIMIT parameters are set to create these ZONES (up to four), several things happen when the antenna is
within 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 (if 4 value is included in SYSTEM TYPE). Timeout and re-target will continue until
the satellite is re-acquired and tracking can resume.
2. “BLOCKED” will be displayed in the TRACKING window wherever the antenna is inside one of the zones.
3. A contact closure to ground (or an open if the blockage logic is reversed – See SYSTEM TYPE 16 value) is
provided on the SW2 terminal of the Terminal Mounting Strip. This Switch output provides a “Blocked”, “RF
Radiation Hazard” or “FCC TX Mute” logic output. When the antenna exits the zone it will be on satellite,
tracking and the SW2 logic contact closure will open.
The lower and upper limits are user programmable and are stored in NVRAM within the ACU parameter list.
AZ LIMIT 1 is the Lower Relative AZ limit (this is the more counter-clockwise of the two points, even if it is
numerically larger). AZ LIMIT 2 is the Upper Relative AZ limit (the more clockwise of the two points) for
pattern mapping of ZONE 1. Enter the elevation value that represents the top of the blockage between the
two azimuth limit points in the EL LIMIT 12 parameter.
AZ LIMIT 3 is the Lower Relative AZ limit (CCW point) and AZ LIMIT 4 is the Upper Relative AZ limit (CW
point) for pattern mapping of ZONE 2. Enter the elevation value that represents the top of the blockage
between the two azimuth limit points in the EL LIMIT 34 parameter.
AZ LIMIT 5 is the Lower Relative AZ limit (CCW point) and AZ LIMIT 6 is the Upper Relative AZ limit (CW
point) for pattern mapping of ZONE 3. Enter the elevation value that represents the top of the blockage
between the two azimuth limit points in the EL LIMIT 56 parameter.
AZ LIMIT 7 is the Lower Relative AZ limit (CCW point) and AZ LIMIT 8 is the Upper Relative AZ limit (CW
point) for pattern mapping of ZONE 4. Enter the elevation value that represents the top of the blockage
between the two azimuth limit points in the EL LIMIT 78 parameter. If your ACU software includes 5 volt
polarization you will not see these AZ & EL LIMIT parameters.
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. Refer to “Functional Testing” for instructions on how to
simulate
a manual BLOCKED condition to test SW2 logic output.
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 is also used to control a Dual Antenna Arbitrator panel to switch the
TXIF & RXIF signals from Antenna
“A” to Antenna “B” when Antenna “A” is blocked, 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).