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1-18 Q16. What term is used to describe a situation in which atmospheric temperature first increases with altitude and then begins to decrease? RADAR PRINCIPLES OF OPERATION Radar systems, like other complex electronics systems, are composed of several major subsystems and many individual circuits. This section will introduce you to the major subsystems common to most radar sets. A brief functional description of subsystem principles of operation will be provided. A much more detailed explanation of radar subsystems will be given in chapters 2 and 3. Since most radar systems in use today are some variation of the pulse radar system, the units discussed in this section will be those used in pulse radar. All other types of radar use some variation of these units, and these variations will be explained as necessary. RADAR COMPONENTS Pulse radar systems can be functionally divided into the six essential components shown in figure 1-16. These components are briefly described in the following paragraphs and will be explained in detail after that: Figure 1-16.—Functional block diagram of a basic radar system. · The SYNCHRONIZER (also referred to as the TIMER or KEYER) supplies the synchronizing signals that time the transmitted pulses, the indicator, and other associated circuits. · The TRANSMITTER generates electromagnetic energy in the form of short, powerful pulses. · The DUPLEXER allows the same antenna to be used for transmitting and receiving. · The ANTENNA SYSTEM routes the electromagnetic energy from the transmitter, radiates it in a highly directional beam, receives any returning echoes, and routes those echoes to the receiver. · The RECEIVER amplifies the weak, electromagnetic pulses returned from the reflecting object and reproduces them as video pulses that are sent to the indicator.