User's Manual

TY91/TY92 VHF Radio Installation Manual 11 April 2012
00839-00 Issue AA
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28 Trig Avionics Limited
The following considerations should be taken into account when siting the
Antenna.
 The antenna 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 in a vertical position when the aircraft
is in level flight.
 Avoid mounting the antenna within 2 feet of a GPS antenna, and as far
as practical from any ELT antenna.
 If the simultaneous use of two radio units is required then each
antenna should be as far apart as practicable for maximum isolation.
We would recommend placing one antenna on top and one on the
bottom of the airframe. The Transmit Interlock function must also be
used in this case (section 5.6.8).
 Where practical, plan the antenna location to keep the cable lengths as
short as possible and avoid sharp bends in the cable to minimise the
VSWR.
Electrical connection to the antenna should be protected to avoid loss of
efficiency as a result of the presence of liquids or moisture. All antenna feeders
shall be installed in such a way that a minimum of RF energy is radiated inside
the aircraft.
5.11.1 Antenna Ground Plane
When a conventional aircraft monopole antenna is used it relies on a ground
plane for correct behaviour. For ideal performance the ground plane should be
as large as practical; in any case at least 1 metre square. In a metal skinned
aircraft this is usually easy to accomplish, but is more difficult in a composite
or fabric skinned aircraft. In these cases a metallic ground plane should be
fabricated and fitted under the antenna.
The thickness of the material used to construct the ground plane is not critical,
providing it is sufficiently conductive. A variety of proprietary mesh and grid