Synchronizer The heart of the radar system is the synchronizer.  It generates all the necessary timing pulses (triggers) that start   the   transmitter,   indicator   sweep   circuits,   and ranging circuits.    The synchronizer may be classified as   either   self-synchronized   or   externally   synchro- nized. In   a   self-synchronized   system,   pulses   are generated   within   the   transmitter. Externally synchronized  system  pulses  are  generated  by  some type  of  master  oscillator  external  to  the  transmitter, such as a modulator or a thyratron. Transmitter The   transmitter   generates   powerful   pulses   of electromagnetic energy at precise intervals.   It creates the   power   required   for   each   pulse   by   using   a high-power   microwave   oscillator   (such   as   a   mag- netron) or a microwave amplifier (such as a klystron) supplied by a low power RF source. For  further  information  on  the  construction  and operation  of  microwave  components,  review  NEETS Module   11, Microwave   Principles,   NAVEDTRA 172-11-00-87. Duplexer The duplexer is basically an electronic switch that permits   a   radar   system   to   use   a   single   antenna   to transmit  and  receive.     The  duplexer  disconnects  the antenna   from   the   receiver   and   connects   it   to   the transmitter  for  the  duration  of  the  transmitted  pulse. The  switching  time  is  called   receiver  recovery  time, and   must   be   very   fast   if   close-in   targets   are   to   be detected. Receiver The receiver accepts the weak RF echoes from the antenna   system   and   routes   amplified   pulses   to   the display as discernible video signals.  Because the radar frequencies  are  very  high  and  difficult  to  amplify,  a superheterodyne receiver is used to convert the echoes to a lower frequency, called the intermediate frequency (IF), which is easier to amplify. Displays Most of the radars that FCs operate and maintain have  a  display,  or  multiple  displays,  to  provide  the operator with information about the area the radar is searching or the target, or targets, being tracked.   The usual display is a cathode-ray tube (CRT) that provides a  combination  of  range,  bearing  (azimuth),  and  (in some cases) elevation data. Some displays provide raw data in the form of the signal from the radar receiver, while others provide processed information in the form of symbology and alphanumerics. Figure  1-5  shows  four  basic  types  of  displays. There are other variations, but these are the major types encountered in fire control and 3-D search radars. TYPE  A.—The  type  A  sweep,  or  range  sweep, display shows targets as pulses, with the distance from the left side of the trace representing range.  Variations in target amplitude cause corresponding changes in the displayed pulse amplitude. The display may be bipolar video when used with Moving Target Indicator (MTI) or pulse Doppler radars. TYPE B.—The type B sweep, or bearing sweep, is mostly found with gunfire control radars and is used with surface gunfire to spot the fall of shot.  The range may be full range or an interval either side of the range gate. TYPE  E.—Two  variations  of  type  E  are  shown. Both provide range and elevation or height of a target. These are associated with height-finding radars and are 1-6 DUPLEXER RECEIVER SYNCHRONIZER TRANSMITTER DISPLAY SUPPORT SYSTEMS COOLING AIR POWER CONTROL GROUP Figure 1-4.—Basic radar block diagram.