EXC-GT – FM super-compact transmitter series
User’s manual – Page 17 of 98
reference, the air flow rate required for proper functioning of a 1 KW transmitter must be at least 500 cubic meters per hour.
Evaluate this element in proportion to the power supplied by the model you are installing.
If the device is placed on a rack, the rear door of the rack can not usually be secured. If the system must be completely
enclosed, a ventilation and air removal system must be created. To encourage air flow, a flange can be installed at the
ventilation outflow, to which a hot air discharge conduit can be connected to the exterior. In this case, it is important to
remember that the transmitter’s internal fans are low pressure units and that it is fundamental for an exhaust fan to be installed
on the air discharge conduit.
The best solution is to keep the room at 20-25°C. Thermal insulation and effective ventilation via a fan controlled by a
thermostat generally present the most advantageous solution.
Excessive concentrations of moisture and/or dust in the air or in the room may cause a condensation build-up in the
transmitter. If the system is periodically switched on and off, this can trigger destructive electric arcs and short circuits, and thus
cause damage that is not covered by warranty.
6.3.c Electrical
conditions
The mains capacity must be proportionately designed to adequately support the device’s power consumption (including a
sufficient safety margin).
The power supply nominal range comes from 185 to 265 V
AC
(nominal voltage single-phase 230 V
AC
). Upon request, some
power models are available with a 400 V
AC
three-phase power supply.
Mains fluctuations and electrical discharges due to weather or nearby industrial machinery may cause significant trouble,
especially in mountain areas and in locations close to industrial areas.
In such cases, it is advisable, if not indispensable, to install a protector, an insulating transformer, or possibly an
electromechanical mains voltage regulator. Upon request, SIEL can provide all of these accessories.
Even though the mains regulator allows for a wide incoming voltage range, it is important to avoid operating using high
impedance mains lines in proximity to the lowest permitted AC limit: if the line falls below a given value while fully loaded, the
control circuit for the lowest AC limit may trigger a very dangerous oscillating on/off cycle. In such cases, we recommend using
a stabilizer on the external line.
Since the total cost of the system, inclusive of broadcasting equipment, antenna system, and installation, is rather high, a
certain percentage of the budget should be set aside for purchasing and installing suitable protection and conditioning facilities.
Depending on the location, the percentage of the total cost should be approximately 10-20% of the total amount. However,
such additional costs will be amortized very quickly since the device operates under ideal conditions; as such, its useful life will
increase and, in particular, the incidence of accidental breakdowns due to ambient or mains trouble will be reduced.
6.4
Wiring the device
This section describes the minimum connections required to place the transmitter in operation.
6.4.a
Wiring into the antenna
Connect the
RF OUT
connector (
2
par. 5.2 ref. [10]) to the antenna or to the next RF amplifier via a high-quality 50 Ohm shielded
coaxial cable equipped with the appropriate connectors.
It is indispensable that only low-loss cables be used when connecting directly to the antenna: in such cases, Celflex or another
similar ½" cable is recommended. Larger cables must be connected using flexible terminal ends from the smallest section, in order
to avoid mechanical stress on the output connector.
,
It is very important to ensure that the antenna, cables, and connectors have the correct impedance and are
appropriate to the transmitter’s nominal power level.
,
The antenna must be suitable for FM broadcasting and able to resonate at the operating frequency with the minimum
possible SWR.
,
The antenna must be grounded via a copper braid of suitable cross-section to prevent lightening or static electricity
from reaching the amplifier through the antenna cable.
6.4.b
Connection to modulation signals
Connect the
LEFT
[21] and
RIGHT
[22] modulation inputs, or the
MPX
input [17] alternatively, based on your desired operating
mode (monophonic or stereophonic) and the type of source being used (mono, stereo, or multiplex signal); refer to the information
provided in Chap. 7.
