SV-COM-X83 Transceiver and Panel Installation and Configuration
SkyView HDX System Installation Manual - Revision E 15-9
• Where practical, plan the antenna location to keep the cable lengths as short
as possible and avoid sharp bends in the cable to minimize the VSWR (voltage
standing wave ratio).
• Double-shielded coaxial cable is superior to single shield coax – more of the
transmit power will be coupled to the antenna, and less received signal will be
lost.
• 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.
15.2.6.1 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 very large
compared to the wavelength of the transmission, which is approx. 7.5 feet (2.29 m). In a
metal skinned aircraft this is usually easy to accomplish, but is more difficult in a
composite or fabric skinned aircraft. In such cases, a metallic ground plane should be
fabricated and fitted under the antenna.
As the ground plane is made smaller, the actual dimensions of the ground plane become
more critical, and small multiples of the wavelength should be avoided, as should circles.
Rectangles or squares are much less likely to create a critical dimension that resonates
with the transmissions. 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
solutions are available. Heavyweight cooking foil meets the technical requirements, but
obviously needs to be properly supported.
15.2.6.2 Antenna Cable
When routing the cable, ensure that you:
• Route the cable away from sources of heat.
• Avoid routing antenna cables together.
• Route the cable away from potential interference sources such as ignition
wiring, 400Hz generators, fluorescent lighting and electric motors.
• Allow a minimum separation of 1 foot / 12 inches (30.5 cm) from an ADF
antenna cable.
• Keep the cable run as short as possible.
• Avoid routing the cable around tight bends.
• Avoid kinking the cable even temporarily during installation.
• Secure the cable so that it cannot interfere with other systems.
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