T674K 40kW UHF TV Transmitter Description

The ITELCO T674K is a 40 kW television broadcasting transmitter with common amplification of vision and sound carriers, operating in the UHF band.

This equipment fully complies with safety of personnel rules specified in IEC215.

Each unit is designed to be easily removed and individually checked.

Exciter

The exciter is designed to be used in common amplification transmitters; it is composed of several plug-ins for easy servicing and simplified updating in the future.
All routine on-air adjustments are screwdriver adjustable from the front panel; an etender board is self-contained for servicing.

Driver Amplifier

the driver amplifier is composed of four solid state amplifier units W612 and a power coupler unit H 613, in order to reach a driving power of 420W at the input of the final stage.
Each amplifier unit has built -in its proper switch mode power supply and is self-protected againts overtemperature, overcurrent, overvoltage, overdrive and high reflected power.
A set of LED shows the status of the unit and a set of test points make possible the reading of the most important parameters.

Final Amplifier

The final amplifier employs the I.O.T. (Inductive Output Tube) 7360 working in common amplification mode and delivering around 41kWps. The I.O.T. assembly is mounted on a trolley and can be slided out in order to facilitate tube replacement : a unique connection to the output coaxial line has been designed in order to easily disconnect the I.O.T. assembly.

Power Supplies

The beam power supply is contained in a separate protected enclosure in the rear side of the driver cabinet and the components are attainable only by opening a door locked by a latch. Inside the enclosure takes place the HV transformer (mounted on a trolley in order to facilitate its removal), the HV rectifier, the smoothing circuit assembly, the HV limiter and the crowbar performing the I.O.T. protection against internal arcs. The filament power supply unit, the grid power supply unit and the magnet pwer supply unit are contained in a separate protected enclosure in the rear side of the final amplifier cabinet, and are attainable only by removing a panel locked by a latch.

All the efective voltages and currents can be measured and displayed by means of the graphic display located on the front panel of the G021 transmitter control unit; any adjustment of the voltage of the different power supplies can be done directly from this unit.

Transmitter Control System

The transmitter control system is involved in three different operations: The transmitter control system consists of four main sub-systems linked up according to a master-slave architecture; the G021 is the master that manages three slave units called Data Acquisition Interface (D.A.I.). Each Data Acquisition Interface manages several sub-units (e.g. all detectors as cooling liquid flow and temperature, phases monitor, forward and reflected power, etc. and all the power supplies, the drier and the exciter): for each of them it performs the A/D conversion of the electrical magnitudes to monitored, the D/A conversion of the settings, the data storage and the data communication management.

The data communication between each D.A.I. and the master unit is via optical fiber, at a bit rates of 40 kbit/s. In order to not loose the memory in case of mains lack, all the transmitter settings, readings and alarms are stored by a battery backed-u RAM.

Last but not least, all the controls and the signals can be remoted via an optional RS232 interface.

Safety Key Locks

In order to assure safety conditions to the personnel involved in the maintenance and repair of the transmitter all the units containing components connected to dangerous voltages are protected and the door can be opened only after opening of the mains breaker and closing of the earthing switch.

Water Cooling System

The water cooling system is single-circuit type and the circulating liquid is tap water with antifreeze. This heat is dissipated to the atmosphere through a water-air heat exchanger.

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