User's Manual

TRM-300 / Integration guide
F070033PT_5.1_en
Page 20 of 26
en
The GPS technology uses radio signals from earth orbiting satellites to establish the location co-ordinates.
Maximizing the view of clear, unobstructed sky is essential for optimum performance.
In places where adequate signals from multiple satellites are not available (usually because a view of a wide
area of the sky could not be established) the GPS feature of your terminal will not work. Such situations
include but are not limited to:
- Underground locations.
- Inside of buildings, trains, or other covered vehicles.
- Under any other metal or concrete roof or structure.
- Between tall buildings or under dense tree-cover.
10.3 ANTENNA INSTALLATION
The antennas must be placed in areas with a good RF field, where the signal strength is adequate. Relocate
the antennas in order to avoid near field obstructions or to get appropriate polarization.
Regarding the cable needed between each antenna and the TRM-300, use low-loss coaxial cables and
connectors, with 50 ohm characteristic impedance. Every additional cable, adapter, and connector increases
the loss of signal power.
Electronic devices can cause interference, which affects the performance of the TRM-300. Do not place the
antennas close to electronic devices or other antennas.
Using two TETRA terminals nearby may cause interference between them, for example when these two
devices are in the same vehicle. If this happens, separate the terminals until the interference disappears.
When designing the hardware application in which the TRM-300 is integrated, it is important to take care of
TETRA RF emissions. Do not place any sensitive components near the TETRA antenna, such as the GPS
antenna.
At high or exposed sites, the use of a lightning arrester is recommended. Should a lightning strike occur,
most of the energy should be diverted to ground leaving the product with little or no damage.