User's Manual

DMR repeater 18/02/2011 Versione 1.3
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The equipment is designed to be powered by a safe supply source which grants a double insulation of output
voltage from dangerous voltages. The electric plant must contain a switch to cut off power supply lines,
according to national law and directives.
It is recommended to use power supply sources with low impedance output stage to make the hot swap
controller of PSU properly work. For example, if power supply has an output filter with an inductive equivalent
impedance, a capacitor can be added in parallel in order to reduce the resulting output impedance.
Power supply cable dimensions must be calculated for a maximum current absorption of 7A @13.2V DC, or 4A
@24V, or 2A @48V, in order to avoid significant voltage drop, especially after fast transient. They should be
protected by a fuse or a short circuit protection system which should be placed as near as possible to power
supply source.
The transceiver is equipped with a couple of automotive type fuses, placed near power supply input
connector, for short circuits protection. This type of fuses is designed for battery up to 55 Ah; for bigger
battery power, other more effective devices should be placed before the transceiver to grant a correct power
cut off.
It is also recommended to connect a good ground reference to the rack and to its metal components, by using
both central pin of power supply connector and the screw on the right side of the rack. A second screw for
ground connection is place on the back side of the rack.
5.3.4 ANTENNA
Antenna discharger are recommended to prevent damages due to eventual atmospheric discharges. These
devices should be placed on antenna connection cable, just before equipments installation shelter, and they
must be connected to an optimum ground reference.
Attention must be paid also to connect the eventual diversity receiver to the radiant system: the input of this
receiver is directly connected to BNC connector on the back side of the rack, without any filter. The
corresponding antenna must be placed far enough from the transmitting antenna in order to avoid receiver
desensitization and to get the correct isolation. To avoid any problem, it is recommended to insert a notch or a
pass-band cavity to protect the receiver.
If an external branching is connected to the equipment, it must be designed to ensure the needed isolations
between transmitter and receivers.
5.3.5 HUMAN EXPOSURE
FCC Guidelines described in the OET Bulletin 65, state limits for maximum permissible exposure (MPE) and
specify the maximum power density for “General Population/Uncontrolled Exposure”.
This limit is 0.2 W/m² for VHF band (30-300 MHz) and f/1500 for UHF band (300-1500 MHz). It implies a
constraint in terms of the minimum distance which people must keep from transmitting antenna, in order to
maintain the human exposure under the allowed limit.
With the assumption that a collinear omnidirectional antenna is used with a medium/high gain of 8dBi (=6.3
numeric) and that the transmitter is set at its maximum power (30W, if a +20% is considered as possible effect