R&S®SR8000 Family of VHF FM Transmitters
Air-cooled transmitters for 100 W to 2.5 kW
The synthesizer-based digital exciter generates a frequency-modulated RF signal in the range from 87.5 MHz to 108 MHz. The exciter combines the outstanding specifications of first-rate analog exciters with the reliability of modern digital signal processing.
Analog AF signals as well as digital signals can be processed in line with the bit-serial AES/EBU protocol. Left/right, MPX, RDS or SCA signals can be used as modulation signals.
All signal processing including frequency modulation is performed digitally. By using powerful digital technology and state-of-the-art D/A converters, this exciter meets the high requirements for spurious and spectrum masks. The integrated stereo coder has its own deviation limiter.
All parameters such as transmit frequency, operating mode and modulation mode, as well as properties of the modulation interfaces can be set from menus via the transmitter control unit. The measurement results of the exciter parameters, the exciter state (e.g. operating hours, system events) and modulation data (e.g. frequency deviation, AF level) are evaluated and displayed. An error table supplements the monitoring functions.
Owing to state-of-the-art MOSFET technology, the power amplifier features excellent efficiency and compact design. In the RF amplifier, the signal is increased to a power of approx. 100 W, 250 W, 500 W, 1000 W or 1300 W. The harmonics filter integrated in the amplifier ensures compliance with ETSI standards.
An amplifier controller not only monitors and evaluates protective functions (e.g. overtemperature switchoff, VSWR reduction), but also provides phase correction and controls the output power, thus preventing the amplifier from being overdriven if a transistor fails, etc. This ensures a long life for the individual transistors. Each amplifier is, therefore, self-monitoring and self-protecting.
All relevant operating parameters and fault messages are transferred to the transmitter control unit via a CAN bus interface.
Transmitter control unit
The transmitter control unit handles both internal and external communications, including all control functions. It is integrated on the exciter board. It provides a straightforward summary of the transmitter‘s current status on a display.
Internal communication with the connected components (e.g. amplifier) is handled via CAN bus. The control unit communicates with the external components via Ethernet.
All transmitter and/or amplifier parameters required for diagnostics are available locally as well as remotely via standard (IP) protocol and standard software (webbrowser/SNMP browser). This enables the transmitter status of unattended stations to be accurately evaluated, and any servicing that may be needed to be optimally prepared.
Housing with integrated cooling
Nineteen-inch housing is used for all power classes. The transmitters are air-cooled with internal fans. The surrounding air is drawn in from the front. It cools the modules via conducted channels, and is expelled at the back. The compact fans are extremely powerful and highly efficient.
The fans are monitored at all times and can be replaced during operation, thus making transmitter servicing much easier.
Each amplifier module contains an optimized, highly efficient heat sink. This in conjunction with the elaborate cooling concept ensures effective cooling with only small amounts of air.
The frequency-response-compensated directional coupler integrated in the transmitter and built-in lightning protection round out the