Tesla transmitters

Tesla joint-stock company is the only enterprise on the territory of the Czech Republic manufacturing the full range of certified TV and radio (USW-FM and medium-wave AM) transmitters, and of also all accessories necessary for broadcasting networks. Owing to the Tesla transmitters the Czech and Slovak regional TV companies network is developing, the population of broadcasting equipment is being modernized and replaced. Being one of the most considerable electrotechnical enterprises of the Czech Republic, Tesla has been developing, manufacturing, and selling TV and rado broadcasting equipment for more than 80 years.

The enterprise's history started in 1921, when Elektra joint-stock company was founded, which began construction of a new Gloubetin factory in Prague. At first, the factory was manufacturing light lamps, but very soon it began to work on creating electron tubes for receiving and transmitting devices and on designing the first transmitter. The first medium-wave transmitter was put into operation in 1923. In 1932 the factory became the Phillips's holding, who changed the factory profile into radio receivers manufacturing. After the World War II the factory was nationalized and got the Tesla name. Within several years the enterprise was redirected to heavy electronics manufacturing. In 1953 Tesla became famous having developed, manufactured and set in operation the first TV transmitter of 5 kW in Czechoslovakia (in the Petrzin, Prague).

The present name, Tesla AO, appeared in 1993 when the factory turned into private, and the enterprise leaders became its owners and shareholders. Since April 1953 more than 1,000 Tesla TV transmitters have been installed only on the territory of the former USSR.

TV-transmitters

Tesla TV transmitter

• all the transmitters in their output stages employ powerful field transistors of the Philips Semiconductors Company, which are characterized by high reliability, mismatch withstandability, high amplification factor, and full reiteration of parameters;
• surface-mounting technology is used in manufacturing amplifiers;
• easy frequency tuning within the band is available.

All stated above, along with the introduction of obligatory vibration resistance and temperature cycling testing, provides considerable improvement of the products' reliability. New TV transmitters, as it was before, do not employ any correctors for providing the necessary TV-signal parameters. Such parameters are achieved at the expense of exciter's high quality and necessary linearity and broad band of power amplifiers', which allows keeping output parameters of the transmitter during its proper operation without staff support. In future, this will allow achieving the highest possible ratio between average digital broadcasting power and analog signal on-peak power. The experience of first digital transmitters' manufacturing shows that for analog transmitters' migrating to digital broadcasting it is only necessary to replace modulator and output filter without any overpatching of power amplifiers. Transmitters of up to 200 W are manufactured with common sound and picture signal multiplication. They are designed in bench-top version in a frame of 2U height containing exciter and power amplifier. Transistor transmitters of 1...20 kW are designed with separate amplification in the 19" Evromehanika-type frame and contain 2 main blocks: exciter and power amplifier.

In the second quarter of 2002, the enterprise, together with Artvis NPP, plans to start manufacturing simplified cheaper single-device transmitters of 500 W and 1 kW.

Specially for the Russian market, a IIITV5G metric band transmitter replacing "Zona" I-III-type mother tube transmitter of Czech manufacture was designed. It is a solid-state transmitter, designed for broadcasting TV signal within 175...230 MHz in B/D standard with separate sound and picture signal multiplication. Color signal may have PAL, SECAM, and NTSC coding. The signal is designed for single- or two-channel transmitting two frequency-modulated carrier waves. The sound signal may be stereo- or monophonic, or it may consist of two independent accompanying sound channels.

The transmitter is equipped with one exciter in its main version. The exciter contains a heterodyne frequency source with standard frequency stability for the mixer. The block of precise carrier frequency offset (at the user option), which is phase locked loop from external calibration signal, allows achieving advanced frequency stability. Besides the transmitter-with-one-exciter version, there is also a version with two exciters (or two blocks of precise carrier frequency offset), i.e. with 100% exciter passive reserve.

A transistor output stage is designed for signal power amplification. Amplifiers are equipped with their own overheating protection and standing wave ratio systems and are 'hot' replaceable.

The transmitter is equipped with systems of remote and local control capable of operating in the semi-automatic mode. The two functions of this mode are designed for the transmitter automatic switching on/off depending on video yes/no signal, and also for its automatic switching to the stand-by exciter in the event of the active exciter breakdown. In case of the supply line's emergency outage and its reclosing, the transmitter is started up automatically.

In the first version, remote control and connection with the transmitter are possible only by means of a parallel collecting bus on the transmitting center control panel (the length of the collecting bus may reach 20m). SP 33 series-parallel conversion block is designed for transmitting data and connecting to IBM-type PC.

USW-FM transmitters

Tesla AO manufactures series of transistor transmitters of 20 W...10 kW within a common unified range. Its peculiar properties are as follows:

• standard units are used: amplifying modules, filters, bridge networks, control boards, power feeders;
• powerful field transistors use output stages showing high safety factor during mismatch load;
• all standard specifications for broadcasting signal in any operating modes and conditions (including antenna's functioning during any mismatch load) are observed;
• automatic interchangeability of transmitters by means of interconnection through the remote control ports without any additional devices involved is possible.

The transmitters have in-built RDS coder and stereo processor block. RDS coder software allows using quick information input and the Play List or Paging modes.

DVB-T TV transmitters for terrestrial broadcasting

Since 2000 the enterprise has been manufacturing DVB-T transmitters of 25 W...1 kW. In that very year, experimental digital broadcasting using Tesla equipment was started in the Czech Republic. In 2002 Tesla AO started manufacturing renovated series of digital and analog transmitters according to LD MOS technology.

Antenna-feeder equipment

Antenna-feeder equipment is available both with TV and radio transmitters and separately. The equipment includes antenna systems (AS) of various functions, main feeders for transmitting power of 0,0...40 kW, units summating power of several transmitters for the main antenna (SU), separate feeder channel components (band-pass and rejector filters, power splitters, bridges, artificial antennas, impedance buffers, high-frequency demountable connectors, etc.).

Usage of multiinput antenna systems is one of the ways to provide multichannel broadcasting. One of the AS's advantages is that they are capable of loss-free storing the signals of several transmitters with small frequency spacing without using expensive summating units (SU). The enterprise manufactures a wide range of summating units of 2...6 TV or radio transmitters for their joint operating for one antenna system. Summating unit may include directional dividers, walk switchers, additional rejector filters. Equipment may be manufactured in accordance with customer's unique requirements to performance specifications.

MTP 41 Measuring TV demodulator.

This device is designed for the enterprises and organizations manufacturing or using TV/radio transmitters and other TV broadcasting devices. MTP 41 Measuring TV demodulator includes demodulators of display and sound signals. It enables switching of its four RF inputs and setting the corresponding channel. The device is equipped with a synchronous demodulator and an envelope demodulator. The PLL of the synchronous modulator may be operated both in the gating mode and in the mode of continuous loop bandwidth control. The group delay characteristics can be chosen with correction according to the appropriate standard or with flat group delay. MTP 41 measures input RF voltage, modulation depth; allows measuring levels of carrier frequencies as well as the display carrier to sound carrier levels ratio. MTP 41 is equipped with an automatic control of the output display signal level. There is also manual setting of this level. The modulation pulses distribution is regulated on every line or on lines 15, 328, and 17. MTP 41 allows direct measurement of deviation, of unwanted amplitude modulation, of crosstalks in stereo mode, as well as indication of accompanying sound.

Provided by Tesla.

next >>