SkyTrac Systems Ltd.
Document Rev. 01.020 DOC0334 Page 44 of 49
Restricted Proprietary and Confidential Information
11 APPENDICES
11.1 Appendix A: Causes of RF Interference
Some subscribers have contacted Iridium
®
regarding the loss of signal quality when they operate
their equipment near active INMARSAT terminals.
The power with which INMARSAT units transmit can overpower the Iridium
®
unit’s ability to properly
maintain a quality connection with the Iridium
®
satellite constellation. INMARSAT terminals are often
found in the same locations as Iridium
®
subscribers’ — generally airports and harbors (especially
aboard naval vessels).
In relation to the Iridium
®
unit’s antenna, the location of the INMARSAT unit’s antenna plays a
significant role in determining the degree of signal degradation an Iridium
®
subscriber will
experience. All Iridium
®
units are susceptible to this interference, regardless of the type of antenna
being used.
Susceptibility to interference from an INMARSAT terminal applies to all Iridium
®
end-user products
(9500 and 9505 equipment, including the L-Band Transceiver (LBT), which is contained in products
developed by SkyTrac Systems). Generally speaking, an Iridium
®
unit located within 15 to 45 meters
(50 to 150 feet, respectively) of an operating INMARSAT mini-M or Standard-C terminal, will likely
experience interruption in the unit’s performance.
Other sources of RF interference such as Globalstar
®
units, radar devices, and broadcast stations
can cause interference for Iridium
®
units, but usually are not encountered as frequently as
INMARSAT terminals.
Mitigation of RF Interference
Degradation of service due to RF interference to the Iridium
®
unit can be significantly improved by
performing either or both of the following actions:
a) Increasing the distance and moving the Iridium
®
antenna off axis from the source of the
interference, or
b) Using an external band pass filter and an external antenna.
In determining the optimal location for mounting an external Iridium
®
antenna in a location where
INMARSAT antennae are also located, be certain that the Iridium
®
antenna is mounted to the side or
behind the INMARSAT antenna as well as above or below it. Also note that the length of the feed
line (the cable running from the Iridium
®
unit to the antenna) plays an important role in the
performance of the unit.
The document reference is online, please check the correspondence between the online documentation and the printed version.
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