MXS System Description and Installation Manual
UM06945
© Sagetech Avionics 2022 Proprietary Confidential
Page 22 of 56
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The MXS should have its own antenna(s). An exception can be made for a high-quality diplexer
that enables antenna sharing between an MXS and other UAT ADS-B equipment. Further guidance
on diplexer use can be found in RTCA documents DO-282B and DO-260B, the minimum
operational performance standards for UAT, and 1090 MHz ADS-B, respectively.
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Minimize the distance between the MXS and its antenna(s). The antenna cable(s) must have no
more than 2dB of signal loss from the MXS to the antenna. The 2dB loss equates to approximately
3 meters of aircraft quality RF cable.
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Take care to locate the antenna(s) away from any objects that may disrupt the ground plane for
the antennas, such as doors and landing gear.
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Do not place the antenna(s) near engine exhaust.
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Try to keep the antenna(s) located at least 36” away from other
antennas on the aircraft. The
antennas should be located as close to the centerline of the fuselage as space allows, while trying
to keep the antennas on a flat surface.
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A ground plane is required for most antennas appropriate for MXS. Failure to provide a adequate
ground plane can result in degradation of antenna performance. Ground plane radius should be
roughly the same length as the antenna.
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Use antenna(s) designed for aviation transponders, with the characteristics documented in Table
4-4. Table 4-5 shows some example antennas that can be used.
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Torque mating SMA connectors to 7-10 lb. · in [80-110 N · cm].
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Take care not to over-torque the antennas attempting to reduce a gap between the antenna and
the mounting surface; torque the antenna to the manufacturer’s instructions.
Note: MXS performance (range) may be hindered or damage to the MXS could result if installation does not meet all
of the requirements above.
Table 4-4 MXS Antenna Requirements
Antenna Requirements
Frequency
1030 to 1090 MHz
Polarization
Vertical
Nominal Impedance
50 Ω
VSWR
<1.5:1 between 1030 to 1090 MHz
RF Power
500 W Peak
Radiation Pattern
The gain must not be less than the gain of a matched quarter-wave stub
minus 3 dB over 90 percent of a coverage volume from 0 to 360 degrees in
azimuth and from 5 to 30 degrees above the ground plane when installed at
the center of 1.2 m (4 foot) diameter (or larger) flat circular ground plane.
Mounting Location
Center of fuselage on the Top and/or Bottom side is ideal location.
