FSG 90F System
3. Installation
November 2000
Page
23
W. Dittel GmbH
3.4.3
Antenna installation
Your radio
FSG 90F(X)
is only as good as the antenna!
For operation, a vertical polarized 50 Ohm broadband aircraft COM antenna is required.
The antenna must be able to radiate RF energy evenly and omnidirectional:
•
First of all, look-up the aircraft's manual for antenna installation instructions.
•
The antenna installation location must be carefully planned. It would be the best to
consult the aircraft certifying inspector. In order to achieve best results into all
directions, installation instructions must be fully complied with.
•
For aircraft with metal fuselage, we recommend our antenna, article No. W00066.
The antenna is mounted vertically (as possible) on or under the fuselage. Location
should be even away from horizontally screening metal parts like propeller,
undercarriage, vertical metal fins etc., for maximum radio range into all (horizontal)
directions.
•
Distance to other aircraft antennas, like another COM, NAV antenna, should be at
least 1.5 m/5 ft. When using two radios
FSG 90F(X)
, a distance of 1 m/3.3 ft. between
COM antennas is sufficient.
•
The antenna mounting area should be as flat as possible.
•
The metallic contact between aircraft surface/structure and the antenna cable outer
conductor (shield) must be robust. The electrical contact shall remain continuously
good safe against vibration.
•
For wood and fiberglass (GRP) aircraft, 3 or 4 aluminum counter weight strips (ea.
60 cm/2 ft. long - 5 cm/2 in. wide) are recommended, but shall be placed (mostly)
horizontally with a (if possible rectangular) shape as a star or cross.
•
These counter weights must be centrally screwed together with the antenna socket,
with continuous, electrically good contact.
•
Alternatively, for aircraft with non metallic surface structure inside the fuselage, a
metal foil (min. 60 x 60 cm/2 ft. x 2 ft.) can be glued in. The antenna socket will then
be placed in the foil center, together with a metallic ground contact support plate.
•
For aircraft with fuselage and/or tail-fin made of non conductive material our vertical
folded top antenna, article no. F10057, is suitable. Installation is made best during
manufacturing the tail-fin. A installation drawing is available on request.
IMPORTANT: Carbon fiber is conducting and may shield the antenna!
•
Careful sealing of all openings of the outer skin is mandatory. Make sure, that
electrical contacts remain continuously good, even under bad environmental
conditions.
•
Use only high quality 50 Ohm coax cable type RG-58C/U. Avoid any sharp cable
bend (radius > 50 mm), and any excessive coax cable length.
•
Place all wiring including antenna cable distant to other wiring which carries heavy
AC currents, and distant to any aircraft controls.
•
Any operating kinematics, trimming and all control handles must be absolutely free in
all directions.
•
Ensure the BNC antenna plug is not shortened between inner and outer connector
(Ohmmeter). Resistance 0.0 Ohms indicates a short inside antenna connector, while
some 0.6 to 1 Ohm indicates the antenna cable resistance, while an internally (static)
protected antenna is used. A whip antenna is tested for low resistive contact between
inner cable conductor and radiator, and outer conductor to counter weight.
•
Check the antenna matching using 50 Ohm SWR meter over the whole frequency
range for SWR < 3:1. It may be helpful/necessary to change slightly the length of the
middle radiator, or counter weight length for optimized antenna efficiency and
matching.
•
REMEMBER: A good antenna is the best RF amplifier!
