ABSTRACT
This chapter examines transmitter facilities design, audio processing, amplitude modulation (AM) transmitters, antenna system, coupling/phasing system design, diplexing AM stations, modern moment method computer proof-of-performance and analysis, synchronous AM operation and AM antenna system maintenance. It examines AM radio performance measurements and AM radio antenna system and field strength measurements. The technology behind AM broadcasting has considerably evolved since the first broadcast around 1920. AM broadcast signals propagate via groundwave during daylight hours and also via ionospheric reflection during night-time hours. This reflection causes AM stations to be heard at great distances from the transmission site. An ideal AM signal that is sine wave modulated 100% has two sidebands each containing 25% of the audio. Every transmitter has an output matching network whose phase shift rotates the sidebands relative to carrier between the antenna terminal and the RF final amplifier.
