ABSTRACT
Very high frequency (VHF) radio has long been the primary means of communication between aircraft and the ground. The system operates in the frequency range extending from 118 MHz to 137 MHz and supports both voice and data communication. This chapter describes the equipment used and the different modes in which it operates. VHF communication is used for various purposes including air traffic control (ATC), approach and departure information, transmission of meteorological information, ground handling of aircraft, company communications and also for the Aircraft Communications Addressing and Reporting System (ACARS). VHF aircraft communications take place in a number of allocated channels. The depth of modulation of an RF carrier wave is usually expressed in terms of percentage modulation. The chapter shows typical speech amplifier characteristics with and without compression. Modern aircraft VHF communications equipment supports both data communication as well as voice communication.
