ADS-B FDL-978 Series and
Lite Series Installation Manual
Document No. 87343 Rev G
2-18
FFS Copyright © 2016 All rights reserved.
2.9 Wiring Considerations
Cables with solid cores should not be used. Cables should be selected based on
the wear characteristics of their insulation material, including temperature rating,
resistance to solvents and oils, and flammability. Most inexpensive commercial
data cables have poor flammability properties.
The connection from the FDL-978 Lite Series and FDL-978-XVR Transceivers to the TC978
Controller uses a minimum of six signal lines; the TMAP pair, the Power and Ground pair, and
the Remote On discrete line plus associated ground line. In a certified installation, MIL-W-
16878E/4 or equivalent wire should be used. Wire gauge should be 24 American Wire Gauge
(AWG) for all wires. Shielded, twisted wiring is recommended for the TMAP pair (and all serial
data communication pairs) to improve electromagnetic emissions and susceptibility – one twist
per 1 to 2 inches is adequate. Other pairs in the bundle can also be twisted, but are not
required.
The distance between the FDL-978 Lite Series and FDL-978-XVR Transceivers and the TC978
Controller is limited by the impedance of the wire between them. The TC978 is powered from
the transceivers, not from aircraft power. Therefore, the acceptable voltage drop in the power
line limits the wire length. The TC978 needs an impedance of less than 1.0 ohm in the power
line for satisfactory operation. The following table gives guidelines for typical aircraft hook-up
wire.
Different brands may vary – check your supplier for details.
Gauge
Miliohm/ft
Length for 0.5 ohm
24 AWG
30.2
33.2 ft
An alternative to a harness built from individual wires, particularly for a long cable run, is to use
a multi-core cable. Aviation grade cable with six or more cores is often more expensive than the
individual wires.
2.10 UAT Antenna Installation
The UAT antenna should be installed according to the manufacturer’s instructions.
Selecting appropriate UAT antenna locations is critical to the proper performance of the FDL-
978 Series and FDL-978 Lite Series. The following considerations should be taken into account
when selecting the Antenna location.
The antennas should be well removed from any projections, the engine(s) and
propeller(s). It should also be well removed from landing gear doors, access doors or
others openings which will break the ground plane for the antenna.
The antenna should be mounted on the bottom and or top surface of the aircraft and in a
vertical position when the aircraft is in level flight.
Avoid mounting the antenna within 3 ft of the Automatic Direction Finder (ADF) sense
antenna or any Communications Receiver (COMM) antenna and 6 ft from the
transponder and Distance Measuring Equipment (DME) antennas.
