User guide

SATELLINE-3AS NMS / NMS Epic / NMS 869 / VHF

User Guide, Version 1.0

14.3

Antenna installation

14.3.1

Hand-held equipment

-wave antenna (wavelength at frequency of 450 MHz is approximately 70 cm)

Helix-antenna

Antennas are installed directly to the TNC type antenna connector at the upper part of the radio

modem.

14.3.2

Mobile equipment

-wave antenna

-wave antenna

The ideal installation position is vertical, and there should be at least 0.5 m of free space

around the antenna. In small systems a -wave antenna is sufficient. A separate ground plane

should be placed under the antenna (vehicle rooftop or the engine hood or trunk door are

usually suitable). In problematic cases the most suitable type is a -wave antenna. It can be

installed directly at the top of a pipe with the added benefit of gaining as much as free space

around the antenna as possible. In cases that the antenna cannot be directly connected to the

TNC connector of the radio modem, a coaxial cable with 50 impedance must be used

between the antenna and the TNC connector.

14.3.3

Base stations

Omni-directional antennas ( - , - or 5/8-wave antenna)

directional antennas (yagi /multi-element antenna or corner antenna)

The antenna should be installed in a vertical position. The exact location of the antenna

depends on several factors, such as the size of the overall system and the coverage area terrain

contours. A rule of thumb is that the base station antenna should be located at the highest point

of the coverage area and as close to the centre of the coverage area as possible. The base

station antenna can also be located inside a building, if the walls of the building do not contain

metal.

NOTE!

Because of the high transmission power of SATELLINE-3AS(d) NMS Epic radio modem,

only an external antenna is allowed. A whip-antenna directly connected to the antenna

connector must not be used.