5. Overview of the Facilities
(2) Transmission facilities

Figure 9 System Diagram of Transmission Facilities

Solid line is RF signal; dotted line is control signal. Digital transmitter Tokyo: duplexed ( 1 ) Transmission facility at Tokyo ・ The transmission facility is located in the master room on the 7th floor of the DRP office in Shiba Park Studio Building. ・ The transmission equipment is made in duplex. Both the single-system and the double-system can respectively output 2.4kW-class transmission waves. A cross-over wave-uninterruptible switch that incorporates a 3dB coupler has been adopted for an output coaxial system that can switch the working transmission equipment to spare transmission equipment without interruption of waves. ・ The power amplifier unit of an individual transmission system has 10 sets of 300W output SSPA (Solid-State Power Amplifier) in parallel configuration. ・ An adaptive digital collector circuit that monitors non-linear characteristics of the power amplifier of a transmitter and makes automatic compensation is incorporated in the exciter to amplify OFDM waves. ・ Optical cables are used between the master room and the transmitter room. ・ A water-cooled system has been adopted to cool down the transmitter because the system costs little and occupies not much space. ( 2 ) Transmission facility at Osaka ・ The transmission facility is located in the master room on the 21st floor of the DRP office in the Twin 21 MID Tower Building. ・ The transmission equipment was installed as a single system after cost and installation space were considered. However, the following measures have improved reliability. ・ Installation of working and spare exciters. ・ Installation of spare power amplifier ・ Use of multiple cooling fans ・ Four sets of 200W-output SSPA have been installed for the power amplifier unit. If one of the four sets fails, the other three sets of SSPA and the AGC function of the exciter can ensure rated output automatically, which is called an "active spare system." ・ STL (Studio-Transmitter Link) in 10GHz band links the master room with transmission stations. ・ The transmitter in Osaka radiates relatively less heat than the transmitter in Tokyo. Thus, heat of the transmitter is radiated into the air in the room with a built-in cooling fan, which is then cooled by the air conditioner in the room.