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GeminiG3 - User Manual
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2.5.2 Planning
Referring to Figure 5, the GeminiG3 radiomodem commonly uses three separate antennas:
•
“T” - Main transceiver -
Constraints are the limit of 50 cm (see section 2.5 above) and omni-directional factors
•
“R” - Auxiliary receiver –
Constraints are the receiver spacing of at least 5/8
λ
(wavelength) from transceiver antenna and
omni-directional requirements
•
“G” - Global Positioning System (GPS)
Constraints are TX spacing of at least 24-in/60.96 cm from all transmitting antennas and a clear
view of the sky.
Figure 5 - Antenna spacing
For the optimum antenna spacing at the frequency you are using, consult System Engineering.
For installation of ground-plane dependent antennas, the center of the metal surface used for mount-
ing is preferable for best omni-directional pattern. For ground-plane independent antennas, installa-
tion may be close to the edges of the surface.
Install the antennas in one of the following positions:
•
Most preferred for all antennas: centerline of roof. For transmitter antenna, it is the ONLY ac-
ceptable position.
•
Less preferred for receiver antenna: trunk lid, providing distance to transmitting antenna is re-
spected whether lid is opened or closed.
•
Much less preferred, but permissible for receiver antenna: left or right rear fenders, just in back of
rear window
•
Least preferred, but permissible for receiver antenna: left or right front fenders, ahead of wind-
shield
Proximity to other vehicle-mounted antennas may cause mutual interference especially at higher fre-
quencies.
G
MPE
≥
5/8
λ
(700MHz: 9.57"/24.3cm
800MHz: 9"/23cm
UHF: 18"/46cm)
R
T
50cm
19.7in.
≥
24in.