photo RIZ Transmitters OR 10 K-06 Short Wave Broadcasting Transmitter Type RIZ OR 10 K-06 is a standard amplitude modulated transmitter, designed for operation within SW broadcasting bands between 3,2 and 22 MHz with carrier power of 10 kW.

It meets all CCIR recommendations for this type of service.

The transmitter is built as a self contained, compact and light-weight unit. Therefore, it is very suitable for installation in containers for fixed or transportable stations. Functional layout of different parts and components ensures good survey and easy access.

All control and monitoring elements are placed on the front panel of the transmitter. The supervision of the transmitter is facilitated by the use of signal lamps indicating the operating status of the equipment.

The control and interlocking system of the transmitter is designed for easy connection to remote control and supervision circuits.

Particular attention has been paid to reliability. Only modern and highest quality components of current production are used. To minimize spares requirements the number of different components has been reduced to a minimum. The number of electron tubes has been minimized by using transistorized preamplifiers.


* only three tubes are used

* solid state preamplifiers, rectifiers and control circuits

* high reliability and remarkable stability of characteristics

* possibility of remote control and unattended operation

* compact mechanical design suitable for transportable stations

* stand-by configurations, active or passive, if required

* simple and quick installation

* designed to operate in extreme climatic and environmental conditions

* full compliance with all internationally recognized standards and recommendations for AM broadcasting service

* compliance with relevant safety regulations

* minimized running and maintenance costs


The transmitter is designed for broadcasting service with carrier power of 10 kW.
It basically consists of four sections as follows:
RF Chain, AF Chain, Rectifiers, Control and Protection Unit.


Modern solid state technique is applied throughout the RF Chain. Only one tube is used in the final stage - RF2.

RF1 Stage

This unit, consisting of a crystal controlled oscillator, RF preamplifier and linear power amplifier, generates the RF carrier signal. Optionally, instead of the crystal controlled oscillator a high stability frequency synthesizer can be used to fulfil special requirements, such as to operate in a synchronous network of transmitters.
The generated RF carrier signal is amplified in a preamplifier, and in the wide-band power amplifier, capable to drive the final stage.

RF2 - Final Stage

It is designed as a Class C power amplifier, equipped with one ceramic air cooled tetrode 4CX15,000A. Matching to the antenna feeder line is accomplished by means of a PI-L filter network, which efficiently supresses unwanted harmonic components.


Modern solid state technique is applied throughout the AF Chain. Only two tubes are used in the final stage - AF2.

AF1 - Input Stage

This stage consists of a band-pass filter, transistorized voltage and power amplifiers and a phase corrector. Optionaly, a limiter - compressor and a bias compensation unit can be inserted in this stage as well.

Band-pass filter at the input determines the band-width of the radiated AF signal. Afterwards this signal is split and amplified in two separate channels to the level necessary to drive directly the final stage - AF2. To improve the frequency response and to reduce the non-linear distortion, negative feedback is applied.

Optional units significantly improve the transmitter operating characteristics. The limiter-compressor increases the average modulation depth, while application of the bias-compensation unit improves the overall efficiency of the transmitter, by reducing the quiescent currents of the modulator final stage to zero.

AF2 - Final Stage

The AF final stage is designed as a push-pull amplifier operating in Class AB, or in Class B in case that the optional bias - compensation unit is used. It is equipped with two ceramic, air cooled tetrodes 4CX5000A.

The modulating AF signal is led from the secondary winding of the modulation transformer directly to the RF output stage.


This unit consists of elements ensuring sequential switching -on and -off of different stages of the transmitter. Important currents and voltages are permanently supervised during the operation, and reaction to overcurrents, undervoltages and reflection is performed in an appropriate way. Thus, equipment and maintenance staff are fully protected.

Semiconductor integrated technique is used throughout the control and interlocking system. It is designed in such a way that easy connection to remote control systems is possible.


High voltage rectifier and auxiliary rectifiers give appropriate DC supplies to different stages of the transmitter.

All the rectifiers are of semiconductor type.


The transmitter is enhoused in a metal cabinet. The doors in front of the final stages as well as control and protection unit enable easy access to final stage tubes.

The modular design of all low power stages and control system also facilitates maintenance.

Cooling of the transmitter is by air, using a built-in blower. The air intake can be either through a side wall, or through the bottom of the transmitter. The air outlet is above the final stage tubes.


Normal Operation

The transmitter is designed for continuous 24- hour operation with an average modulation depth of m=60% and peaks up to m=100%.

Test Operation

The transmitter is designed for test operation with a sinusoidal signal, frequency 1 kHz, and a modulation depth of 100% for a duration of 60 minutes.


The transmitter can withstand, without damage, a short duration of AF input signal, fm = 1 kHz, 6 dB above the level required for 100% modulation.

Stability of Technical Data

The technical data stated in this specification are guaranteed for mains voltage tolerance between +5% to -10%, with the exception of RF output power, the consumed power, efficiency and carrier shift.

Change of Operating Frequency

Necessary frequency changes can be easily executed by operating staff within less than two minutes.

Power Supply
Mains voltage 3 x 380 V / 220 V, +5%, -10%
Power input (fm=1kHz/m=1) 40 kVA
Mains frequency 50 Hz ±2 Hz
Power factor cos phi greater than 0.9
Modulator Input
Input impedance (from 60 to 10000 Hz) nominal 600 Ohms balanced
Input level (for fm=1 kHz, m=1)
(0 dBm=0,775 V across 600 Ohms)
-4 to +10 dBm
Transmitter Output
RF output load impedance 50 Ohms unbalanced
Permissible VSWR s less than 2
Climatic Conditions
Temperature in transmitter hall +5 to +45 C
Max. altitude above sea level 2000 m
Relative humidity less than 90%
RF Output Power
Carrier power in the range 3.2 to 22 MHz 10 kW
RF Exciter
Crystal oscillator with fixed frequency in the range 3.2 to 22 MHz
Frequency precision and stability 2 x 10-6 Hz/day
Frequency synthesizer as option
Modulation System
Type of modulation High level amplitude modulation
Type of emission 20 A3
Bandwith limiting filters 4,5 kHz or 5 kHz available as option
Modulation Characteristics
The ratio of input to output as function of modulation depth (m=30 ... 80%) does not differ by more than ±0,5 dB
Signal to Noise Ratio
Unweighted more than 50 dB
Weighted more than 60 dB
Reference level m=100% fm=1 kHz, sinusoidal
Mains voltage sinusoidal
Spurious Emission
Mean power of any spurious emission supplied to the antenna transmission line below the mean power of the fundamental more than 60 dB
Carrier Shift
Carrier shift at m=90% with fm=1 kHz sinusoidal and
at a constant mains voltage referred to the unmodulated carrier
less than 4%
Overall Efficiency
Overall efficiency more than 40% (fm=1kHz, sinusoidal)
Specifications may change without notice

RF stages AF stages and modulator
Number Type Number Type
1 4CX15,000A 2 4CX5000A


ITU Country
ITU Country