TD 90227GB
2006-09-18/ Ver. C
System Installation
On Site Paging System
10
If an antenna cannot be installed in a normal manner or if the coaxial cable has an
excessively high standing-wave ratio, the antenna tuner can be used to match the
transmitter impedance to the antenna (for example boat installations, culverts, or cellars).
MPT-50
MAT-50
MAT-50
OUT
IN
MPT-50
IN
80%
20%
IN 20%
IN
80%
20%
IN 20%
Terminal
Transmitter
Slave
Transmitter
Central
Unit
Slave
Transmitter
Figure 10. Power divider in HF system.
Antenna transformer MAT-50 is used in HF installations at the output of the transmitters
to provide galvanic isolation from the antenna and protection from over-voltage and
transients caused by lightning.
Power divider MPT-50 is used in HF installations to divide output power from a transmitter;
20% to the next slave transmitter and 80% to the antenna, or to divide power to two
antennas. The two outputs are galvanically isolated from the input so that an MAT-50 is
not needed when MPT-50 is used.
5.4
Antenna Location
An outdoor antenna should be located as centrally and unobstructed as possible within
the designed coverage area. The antenna must not be placed near metal-clad chimneys or
similar structures.
Three alternatives are:
1
On the roof; provides good coverage around the building but usually provides
diminished coverage within the building.
2
On the ground floor; theoretically provides good coverage in the entire building but
may result in uneven coverage due to absorption by floors and other building
structures.
3
On the roof of a lower nearby building; provides good coverage of entire building if
the building is not too wide.
When planning an installation, a coverage test from the intended antenna site should
always be carried out.
When planning the location of an indoor antenna, consideration must be given to the
possible effect of antenna radiation on other electronic equipment.
If several antennas are to be mounted on the same mast the vertical spacing between
antennas should be at least 0.5 m.
If a guying kit is used the attachment point must be at 60% of mast height. When
attaching to a roof frame or wall, at least 25% of the mast height must be included
between the two attachment points.
