R&S®NM8200 VHF Transmitter Family
Air-cooled medium-power transmitters for analog TV
Power amplifier
The air-cooled broadband R&S® VH 8200 A1 amplifier operates in the range from 470 MHz to 862 MHz (UHF bands IV/V). It can be used both for analog and digital signals without requiring any adjustments, which means a smaller inventory of spare parts for operators of mixed transmitter networks.
The output power of each amplifier plugin depends on the modulation mode: 200 W for DVB-T/-H, 300 W for ATSC and 500 W for analog TV (combined). Due to the use of advanced LDMOS technology, the power ampli. ers offer very high linearity, excellent efficiency and compact design. Each amplifier plug-in contains a predriver and a driver stage, eight power transistors and a separate power supply.
An innovative amplifier controller is used, which is identical for all sound and TV transmitters of the Rohde & Schwarz Nx 8000 family. This controller not only monitors and evaluates protective functions (e.g. overtemperature switchoff, VSWR reduction, transistor failure detection), but also provides phase correction and control of the RF output power. Output power control prevents, for example, the amplifier from being overdriven in the event a transistor fails, thus ensuring a long life for the individual transistors. Each amplifier module is, therefore, selfmonitoring and self-protecting.
All relevant operating parameters and fault messages are transferred to the transmitter control unit via the CAN bus interface, which is likewise an innovative feature. The amplifier modules can easily be replaced during operation.
