Position des antennes VHF / XPDR (question technique)

[Olivier02]

Bonjour.
Une petite question : y a-t-il une distance minimale à respecter entre l'antenne VHF et l'antenne du transpondeur pour éviter les interférences (même si les bandes de fréquences sont bien différentes) ?
Si oui, vaut-il mieux placer l'antenne VHF sur le dessus et l'antenne du transpondeur sur le dessous de l'appareil ou le contraire ?
Merci de vos réponses. Je n'ai rien trouvé sur Google et n'ose pas appeler un installateur (vu qu'il ne fera pas le travail ).
Olivier

[Bob]

L'antenne du transpondeur doit obligatoirement être dessous, puisque c'est pour communiquer avec le sol. (Sauf si tu voles surtout sur le dos ! )

Les antennes VHF sont indifféremment dessous ou dessus. Si tu as la place, écarte-la le plus possible de l'autre "ça ne mange pas de pain" .

Je me demande s'il n'y a pas une info à ce sujet sur le site du RSA ? ? ?

[Olivier02]

L'antenne du transpondeur doit obligatoirement être dessous, puisque c'est pour communiquer avec le sol. (Sauf si tu voles surtout sur le dos ! )

Justement, je n'en suis pas certain. Il est vrai que dans la plupart des cas, elle est utilisé par des stations au sol, mais elle sert aussi aux alarmes et résolutions TCAS par des appareils qui peuvent être situés au dessus ...

[Bob]

Extrait du manuel d'un transpondeur Filser :


3.6. ANTENNA INSTALLATION
Particular attention must be paid to the proper antenna installation on the
aircraft so that the specified minimum radiation is ensured. The radiation
pattern needs to be verified per aircraft type. Credit can be taken from
the approval of a similar type.
Normally the antenna will be mounted at the bottom of the aircraft.
However sufficient field strength should also be available above the light
aviation vehicle so that proper detection by ACAS equipped other aircraft
is ensured.
The electrical interference between the antenna and any other
antenna/equipment must be taken into account in such a way that no
reduction of the performance of any other system will occur.
Particular care should be taken to ensure that the interference on the
TRT800 antenna subsystem caused by static electricity is minimized.
Electrical connections to antenna shall be protected to avoid loss of
efficiency as a result of the presence of liquids or moisture.
All antenna feeders shall be installed so as to ensure that a minimum of
radio frequency energy is radiated inside the aircraft. Especially RF
hazard exposure to persons on board the aircraft should be minimized by
appropriate precautions.
The antenna type chosen shall be compatible with the vehicle on which it
is used and the location where it is mounted.

Warning
Radiation Hazards

In order to avoid the possibility of human body damage (e.g.
to eyes) and/or ignition of combustible materials by radiated
energy, a safe distance to the installed antenna must be
ensured by adequate installation provisions.

3.6.1. Location Considerations
· The antenna should be mounted on the underside of the aircraft
and in a vertical position when the aircraft is in level flight
· Avoid mounting the antenna within three feet of the ADF sense
antenna or any other communication antenna and six feet from the
DME antenna.
· If the antenna is being installed on a composite aircraft, ground
planes must be added or a symmetrical Antenna can be installed.
· the antenna should be installed according to the antenna
manufacturer’s instructions.
3.6.2. Blade antenna TRT-ANT-A
The blade antenna is a normal ground plane antenna for installation in
metal aircrafts or where a ground plane (metal plate, min. size 30x30 cm)
can be installed.
Other antenna will be offered by Filser Electronic GmbH when they are
available. For mounting on aircraft made of composites the ground plane
should be as large as possible but not less than 30 x 30 cm for
satisfactory performance. If in doubt please contact the aircraft
manufacturer.

3.6.3. Antenna Cable Installation
When routing antenna cables, observe the following precautions:
· All cable routing should be kept as short as possible and as direct
as possible.
· Avoid sharp bends.
· Avoid routing cables near power sources (e.g., 400 Hz generators,
trim motors, etc.), ignition coil or near power for fluorescent lighting.
· Avoid routing cable near ADF antenna cable (allow at least a 12-
inch separation).
A special cable type (CELLFOIL, or AIRCELL) has low attenuation at
1090 MHz but it is not very resistant against mechanical stress like sharp
bends. Therefore at mounting positions in rudders it requires a careful
design.