User's Manual
Radio Activity S.r.l. 28 / 44
entry) and back or side panels (for air to exit). The cabinet must have a least 15 cm (6 inches) of open
space between the air vents and any wall or other objects.
∞ In case RF transmitter is set for its maximum power, it is active with a duty-cycle near to 100% and
ambient temperature could be above 40°C, a larger respect area must be considered around the rack
and an air forced cooling system should be eventually designed (“FAN” contact of the equipment can
be used to switch on and off an external cooling system). The transmitter is protected against over-
temperature: if the RF mosfet temperature arises over 85°C, the microprocessor will automatically
decrease the generated RF power in order to make the amplifier work in safety conditions. The
nominal RF power will be restored as soon as the mosfet temperature will decrease below 60°C.
4.3 Power supply system
Internal power supply voltage is nominally set to 13.2V dc from battery, with negative pole connected to
ground, and it is protected against polarity inversion, over-voltage, under-voltage, short-circuits.
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 the power supply line is very long a capacitor should be
added in parallel in order to reduce the resulting output impedance.
The power supply input has a built-in RF filter that reduce the inout noise. A ferrite bead should be inserted
in the power supply cable for very low noise applications or for cable length that exceeds 3 meters.
Note: use cable with adequate section and don’t insert inductive devices because they could produce extra-
voltage that activate internal electronic protections giving on/off instability.
Power supply cable dimensions must be calculated for a maximum current absorption of 5A @13.2V DC, in
order to avoid significant voltage drop, especially after fast transient. They must be protected by a fuse or a
short circuit protection system which should be placed as near as possible to each power supply source
(AC/DC and battery).
It is also recommended to connect a good ground reference to the rack, to its metal components and to
KAIROS by using the screw on the rear side of the equipment.
4.4 Antenna
Antenna discharger are recommended to prevent damages due to eventual atmospheric discharges. These
devices should be placed on antenna connection cable, just before equipment installation shelter, and they
must be connected to an good 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 a SMA 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.