THOMSON-CSF TRE 2355

GENERAL DESCRIPTION

HF - Short wave 500 kW broadcasting transmitter

photo Thomson-CSF TRE 2355

Feature

PDM digital modulator.
High efficiency RF stage.
Fast tuning and great stability on all frequencies.
Full A3, DACM, stereo (optional) and high efficiency SSB operation (optional).
Hypervapotron cooling system.
Quick tube changing ("a minute").
Total safety for operating personnel.
Complete local TV screen monitoring (printer optional) and automatic self diagnosis for quick trouble shooting.
Full remote control capability (IEEE 488 or RS 232).

Layout and access

The transmitter is composed of 2 or 3 main sub assemblies (depending on installation) which can be rapidly interconnected on site: wiring and piping between those assemblies are limited to a minimum.

No underfloor duct is required.
Access to all parts of the transmitter is very easy thanks to properly located removable panels.
All necessary items to facilitate maintenance are included in blocks; changing a tube typically requires less than a minute with absolutely no water spill over.
Heavy components, transformer and diode rectifier mainly, are generally located apart from the transmitter on either the same or a different floor.

Description of the transmitter

There are basically two separate amplification lines, RF and AF.

RF circuit

Last refinement of the proven 500 kW RF THOMSON CSF circuits, its structure is unbalanced. Equipped with only 2 tetrodes, the RF circuit amplifies the RF signal from the output of the synthesizer (1 V/50 ohm) up to the rated level (500 kW/50 ohm) in 3 steps:

Transistorized RF 1 stage output: 100W.
TH 562 tetrode RF 2 stage output: 5 kW.
TH 558 tetrode RF 3 stage output: 500 kW.

RF 3 power tube operates in class C. It is modulated through anode control, with automodulated screen. It is followed by three distinct networks in series which ensure the following functions:

Anode tuning and loading.
Harmonic filtering (distributed constants).
Matching to the RF output feeder.

AF circuit

The AF high voltage necessary to modulate the anode of the final RF tube is produced by integration of width modulated pulses at 50 kHz. AF1 generates pulses through a complete digital process which introduces precise precorrection to compensate for non linearity of AF stages. Any carrier variation (DACM or reduced power) may be programmed in the microprocessor system. Transmission of the signal to AF2 and AF3, located on an insulated chassis, is performed through optic fibers. AF1 and AF2 are fully transistorized, while AF3 uses a TH 558 or 573 tetrode.
Double coil, free wheel diode, and low pass filter complete the AF circuit.

Transmitter and frequency control

Transmitter and frequency control units gather the means for controlling, monitoring and insuring internal security of the transmitter, trying to minimize the need for operator intervention. They are based on a microprocessor central unit surrounded with several interface boards to shape data exchanged with the transmitter, the operator, or a remote control computer through an RS 232 or IEEE 488 interface.

Monitoring and trouble shooting:

Through a TV screen located on the front panel of the transmitter. A printer may additionally be connected to get a complete logbook. Most informations displayed locally can be remote transmitted on the bus. An automatic self diagnosis for quicker trouble shooting is performed in case of a fault. Result is automatically displayed on the monitor.

TECHNICAL SPECIFICATIONS
R.F. characteristics
Power output (carrier)	500 kW Reduced power operation DACM operation
Frequency range	5.9 to 26.1 MHz. Extension to 3.9 or 3.2 (optional)
Tuning	automatic on any frequency within broadcast bands (and optional on most frequencies outside broadcast bands)
Transmission type	A3, A3 with DACM, SSB (optional), AM stereo (optional)
Modulation type	digital PDM for anode amplitude modulation
Frequency stability	±2 10^-7 per month (or better optional)
RF output	50 ohm unbalanced SWR less than 2 (300 ohm balanced with balun)
RF harmonics	better than CCIR specifications (50 mW or less on any frequency)
AF characteristics
AF input impedance	more than 5000 ohm balanced between 50 Hz and 7500 Hz, compatible with a 600 ohm balanced line
AF nominal level to achieve	100% modulation at 1000 Hz =0 to +10 dBm adjustable of ± dB by 0.5 dB steps
AF band with	50 Hz to 7500 Hz (or 4500 Hz with a filter) in A3 mode
Frequency response	Reference curve stands within the limits below, measured with a 50% modulation rate. For any modulation between 30 and 80%, the curve stands within ±0,5 dB of the reference curve
Harmonic distortion	50 to 100 Hz: 3% at 30 to 80% 100 to 5000 Hz: 2,5% at 30 to 80%, 3% at 90% 5000 to 7500 Hz: 3% at 30 to 80%
Noise	Unweighted noise referenced to a 100% modulated carrier with a 100 Hz tone less than 58 dB
Modulation capabilities
Maximum modulation factor	100% from 100 to 5000 Hz 80% anywhere in band
Maximum average modulation factor in program operation	70% (can be sustained continuously)
Carrier shift	Less than 5% at 100% modulation with 1000 Hz sine wave
Power supply
Three phases 5,5 to 24 kV (or more optionnally)	1200 kVA
Single phase 220 V	3 kVA permanent
Three-phases 220/380 V (can be internally generated)	50 kVA
Overall power efficiency
70% typically	(64% minimum guaranteed at any modulation on any broadcast band)
Environment
Temperature	+1°C to +50°C (extended optionally)
Humidity	95%
Altitude	1500 m (or more optional)
Specifications may change without notice

TUBE COMPLEMENT
RF stages		AF stages and modulator
Number	Type	Number	Type
1	TH558	1	TH558 or TH573
1	TH562

THIS TYPE OF TRANSMITTER IS INSTALLED IN THE FOLLOWING COUNTRIES
	ITU	Country	ITU	Country
	CTI	COTE D'IVOIRE	F	FRANCE
	GAB	GABON	LBY	LIBYA
	ARS	SAUDI ARABIA