SV-ADSB-470 Installation and Configuration
14-8 SkyView System Installation Guide - Revision AA
and avoid sharp bends in the cable to minimize the VSWR (voltage standing wave ratio).
The SV-ADSB-470 antenna should not be installed within 2 feet (24 inches) of a 1090
MHz transponder (including the SV-XPNDR-261/262) antenna.
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 reception, which is 305 mm. 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 smallest practical ground plane is a square around 130 mm per side; as the
size increases the performance may actually get worse, but will be better by the time the
ground plane is 780 mm on each side. Anything much larger than that size is unlikely to show
significant further improvement.
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.
Antenna Cable
An acceptable cable:
Has less than 3.0 dB loss for the run length needed. For runs less than 17 feet, RG58
is acceptable.
Has a characteristic impedance of 50 Ω (50 Ohms).
If running the antenna cable in a bundle with or in close proximity to the SV-XPNDR-
261/262 antenna cable:
o Has double braid screens or has a foil and braid screen. For runs less than 17
feet, RG400 is acceptable.
When routing the cable, ensure that you:
Route the cable away from sources of heat.
Route the cable away from potential interference sources such as ignition wiring, 400Hz
generators, fluorescent lighting and electric motors.
Keep the cable run as short as possible.
Avoid routing the cable around tight bends.
To Next Page
Loading...
