Home' RTCA Documents for Review : DO-204B, MOPS Aircraft ELT 406MHZ Contents © EUROCAE, 2018
126.96.36.199.3 Antenna Placement with Regard to Other Antennas
The installation manual must state that, as a rule of thumb, 0.9 meters (36 inches)
should be the minimum distance between antennas and if the antenna must be
mounted closer than 0.9 meters, analysis or testing, such as that described in section
§ 6.2.15, will need to be accomplished to ensure the systems do not interfere with
188.8.131.52.4 Antenna Orientation
The installation manual must provide guidance on properly orienting the antenna.
Typically, ELT antennas are oriented as close to vertical as practical, (and should be
optimized based on the design of the antenna), based on the aircraft's normal flight
attitude. The installation manual must also include a recommendation for the ELT
antenna location to maximize the unobstructed view of the sky.
184.108.40.206.5 Antenna Ground Plane
The instruction manual must instruct the installer to ensure the antenna has an
acceptable ground plane.
220.127.116.11.6 Antenna Coverings
The installation manual must state that any additional antenna covering not degrade
Equivalent Isotropically Radiated Power (EIRP), more than 0.2 db within the frequency
band from 406.0 to 406.1 MHz.
18.104.22.168 Internally Mounted Antennas
22.214.171.124.1 Location of an External Antenna Mounted Internally
An external antenna is intended for location and use external to the aircraft. The
installation manual must state an external antenna, which is mounted internal to the
aircraft, be located such that the aircraft structure not reduce the Equivalent
Isotropically Radiated Power (EIRP) transmitted by the antenna by more than 0.2dB
within the frequency band from 406.0 to 406.1 MHz, and the antenna be mounted as
close to the ELT unit as practicable.
126.96.36.199 ELTs with Integral Antennas
188.8.131.52.1 Location of Integral Antenna
For ELT(AF), ELT(AP) and ELT(DT) if the ELT has only an Integral Antenna, the
installation manual must state that the ELT be located such that the aircraft structure
does not reduce the Equivalent Isotropically Radiated Power (EIRP) transmitted by the
Integral Antenna by more than 0.2dB within the frequency band from 406.0 to 406.1
ELT ANTENNA CABLES
184.108.40.206 Antenna Cable Specifications
The installation manual must provide details of the cable specifications and the
maximum and minimum cable attenuation allowed between the ELT and the installed
antenna. The installation manual must state that if antenna cabling is not included as
part of the ELT system, or if it is not used, the antenna cable selected by the installer
meet the specifications of this document.
220.127.116.11 Cable Strain Relief
The installation manual must state that when the coaxial cable is installed, using
acceptable methods, techniques, and practices, and the connectors mated, each end
have appropriate cable strain relief, which is at least 15 cm, (6 in), of excess cable
near the ELT and the antenna.
18.104.22.168 Antenna Cable Routing Over Break Points
The installation manual must state that the antenna cable avoid crossing, to the
maximum extent practicable, over areas known to break apart in a crash, (i.e. where
the tail boom is mounted to the fuselage of a helicopter or the point where the aft
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