User's Manual

TY91/TY92 VHF Radio Installation Manual 11 April 2012
00839-00 Issue AA
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Trig Avionics Limited 27
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 6 or more
cores is often more expensive than the individual wires, and therefore is not
generally a good choice for a certified aircraft. For aircraft where those
considerations do not apply however, an attractive alternative solution may be
to use 3 pair or 4 pair data cable.
Whilst appropriate cables may exist, please note that not all data cable is
suitable for this application. Cables with solid cores should not be used, and
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.
Note: If you are installing more than one Trig TY91/TY92 radio, or
installing a radio with a Trig TT21/TT22 transponder, then bundling
the TC90 and TC20 control head interconnecting wires into one loom
is acceptable and will not cause any interference between the two
units. The same is not true of the audio wiring or antenna wiring –
these should be kept apart using normal wiring practices.
5.10.2 Audio wiring
For any wires carrying an audio signal, a screened twisted pair should be used
to avoid any unwanted signals interfering with the radio installation.
Unscreened wires can act as small antennas and transmissions from other
avionics on the aircraft could be picked up by the radio and heard as
interference in the connected headsets. For example, Mode S transponder
transmissions can be audible as clicking sounds in the headset and cause an
annoying distraction to the pilot.
Correctly terminated screened wiring will limit any unwanted transmissions
being picked up by the radio and should be used on the MIC and PHONE
lines.
5.11 Antenna Installation
The antenna should be installed according to the manufacturer’s instructions.