SkyTrac Systems Ltd.
Document Rev. 02.010
ISAT-100-OPD-SOI
Page 26 of 26
Restricted Proprietary and Confidential Information
7
APPENDIX
B
7.1 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 ships).
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.
7.2 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, 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 either 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.
