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GPS General System Information - V01.03
hopf
Elektronik GmbH
Nottebohmstr. 41 • D-58511 Lüdenscheid • Tel.: +49 (0)2351 9386-86 • Fax: +49 (0)2351 9386-93 • Internet: http://www.hopf.com • E-Mail: [email protected]
2
Accessories
2.1 GPS Antenna
Due to the small signal level an outdoor installation of the antenna is recommended.
2.1.1 Where to install the antenna
Since the antenna is designed to receive data from all directions it must be non-directional.
Because of the high frequency there must be "visual contact" to the satellites.
Visual contact means that no solid or large objects (buildings) may block the view to the
horizon (see drawing
A06
"GPS Reception in 3D and Position Fixed Mode"). Rain, fog and
clouds as well as small objects, e.g. chimneys, at a certain distance may impair the view
minimally.
The larger the visible section of the sky, the longer the post-connected
electronics remain radio-synchronous.
In the standard reception mode (3D) of the GPS system reception from at least 4 satellites is
necessary. In position fixed mode reception from only one satellite is necessary (see
technical description of GPS system). It is also possible to install the antenna behind a non-
coated window.
No additional voltage supply is required to operate the antenna. It is provided via the
antenna cable and is supplied by the BNC connector of the
hopf
GPS system.
2.1.2 Mechanical Structure of the Antenna
The antenna is housed in a round weatherproof plastic casing. The casing cover is arched to
prevent any rain water, snow or other impurities from settling on the antenna.
The mechanical construction (see drawing
A04
"Dimensions of Antenna 4490G10 / 4418A")
consists of sturdy, anodized aluminium or aluminium die-casting and is designed to resist
high winds.
The plastic housing can be installed horizontally as well as vertically to the mechanical parts
(see drawing
A03
"Mounting of Antenna 4490G10 / 4418A"), allowing both wall and flat-roof
installation of the antenna. The antenna cable can be fed either through the base or through
a slot on the side of the mounting flange.
2.1.3 Electrical Structure of the Antenna
As the antenna is non-directional, reception cannot be improved by mechanical shaping as,
for example, with parabolic antennas. Therefore the signal strength at the antenna input is
about 1 x 10
-16
Watts and already below the generally permitted noise level.
An extremely low-noise pre-amplifier is placed behind the antenna in order to feed the
signals to the electronics via an antenna cable. The antenna cable also supplies the voltage
to the pre-amplifier.