Aviation Electronics Technician 1 - Historic Naval Ships Association

CHAPTER 1COMMUNICATIONSAs an Aviation Electronics Technician, you will betasked to operate and maintain many different types ofairborne communications equipment. These systemsmay differ in some respects, but they are similar in manyways. As an example, there are various models of AMradios, yet they all serve the same function and operateon the same basic principles. It is beyond the scope ofthis manual to discuss each and every model ofcommunication equipment used on naval aircraft;therefore, only representative systems will be discussed.Every effort has been made to use not only systems thatare common to many of the different platforms, but alsohave not been used in the other training manuals. It isthe intent of this manual to have systems from each andevery type of aircraft in use today.RADIO COMMUNICATIONSLearning Objective: Recognize the varioustypes of radio communications. Identify thevarious frequency bands and their uses andlimitations.In basic terms, communication is defined as themeaningful transfer of information from one location(the sender, source, originator) to another location (thedestination or receiver). Electronic communication useselectrical energy to transmit the information to becommunicated Since this electrical energy travels at thespeed of light, the transfer can occur within a fraction ofa second. The information must be converted from itsoriginal form of sound, light, or mechanical energy intoelectrical energy. This electrical energy can then betransmitted via wires or radiated through space to areceiver. The receiver must then convert the electricalenergy back into its original form to complete thecommunication cycle.TYPES OF RADIO COMMUNICATIONSRadio communications has become a highlysophisticated field of electronics. All Navy aircraft havethe capability to use the commonly used ship-to-ship,ship-to-air, air-to-air, air-to-ground, and ship-to-shorecommunication circuits. These operations are accomplishedthrough the use of compatible and flexiblecommunication systems.Radio is the most important means of communicatingin the Navy today. There are many methodsof transmitting in use throughout the world. This manualwill discuss three types. They are radiotelegraph,radiotelephone, and teletypewriter.RadiotelegraphRadiotelegraph is commonly called CW (continuouswave) telegraphy. Telegraphy is accomplishedby opening and closing a switch to separate acontinuously transmitted wave. The resulting “dots” and“dashes” are based on the Morse code. The majordisadvantage of this type of communication is therelatively slow speed and the need for experiencedoperators at both ends.RadiotelephoneRadiotelephone is one of the most useful militarycommunication methods. It is used by aircraft, ships,and shore stations because of its directness, convenience,and ease of use. The equipment used fortactical purposes usually operate on frequencies that arehigh enough to have line-of-sight characteristics. Thiscuts down not only on the possibility of the enemyintercepting the messages, but also cuts down on thedistance between the transmitter and receiver.TeletypewriterTeletypewriter (TTY) signals may be transmitted byeither landlines (wire), cable, or radio. The Navy usesradio teletypewriter (RTTY) for high-speed automaticcommunications. The keyboard used with a TTY systemis similar to that of a typewriter. When the operatorstrikes a key, a sequence of signals is transmitted. At thereceiving station, the signals are translated back intoletters, figures, and symbols that are typed onto paperfor use.1-1