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Radar systems, like cars, come in a variety of sizes and have different performance specifications. Some radar systems are used for air-traffic control at airports and others are used for long-range surveillance and early-warning systems. A radar system is the heart of a missile guidance system. Small portable radar systems that can be maintained and operated by one person are available as well as systems that occupy several large rooms.


The large number of radar systems used by the military has forced the development of a joint-services classification system for accurate identification. The Federal Aviation Agency (FAA) also makes extensive use of radar systems for commercial aircraft in-flight and landing control, but does not use the military classification system.

Radar systems are usually classified according to specific function and installation vehicle. Some common examples are listed below:

Search Ground or land based
Track Airborne
Height-finder Shipboard

The joint-service standardized classification system further divides these broad categories for more precise identification. Table 1-1 is a listing of equipment identification indicators. Use of the table to identify a particular radar system is illustrated in figure 1-23. Note that for simplicity, only a portion of the table has been used in the illustration.

Table 1-1. - Table of Equipment Indicators

TABLE OF EQUIPMENT INDICATORS Miscellaneous Identification Installation(1st letter) Type of Equipment (2d letter)
A-Piloted aircraft A-invisible light, heat radiation B-Bombing X, Y, Z-Changes in voltage, phase, or frequency
B-Underwater mobile, submarine C-Carrier C-Communications (receiving and transmitting T-Training
D-Pilotless carrier D-Radiac D-Direction finder reconnaissance and/or surveillance (V)-Variable grouping
F-Fixed ground G-Telegraph or Teletype E-Ejection and/or release  
G-General ground use I-Interphone and public address G-Fire control, or search- light directing  
K-Amphibious J-Electromechanical or Inertial wire covered H-Recording and/or reproducing (graphic meteorological and sound)  
M-Ground, mobile K-Telemetering K-Computing  
P-Portable L-Countermeasures M-Maintenance and/or test assemblies (including tools)  
S-Water M-Meteorological N-Navigational aids (including altimeters, beacons, compasses, racons, depth sounding, approach and landing)  
T-Ground, transportable N-Sound in air Q-Special, or combination of purposes  
U-General utility P-Radar R-Receiving, passive detecting  
V-Ground, vehicular Q-Sonar and underwater sound S-Detecting and/or range and bearing, search  
W-Water surface and under water combination R-Radio T-Transmitting  
Z-Piloted and pilotless airborne vehicle combination S-Special types, magnetic, etc., or combinations of types W-Automatic flight or remote control  
  T-Telephone (wire) X-Identification and recognition  
  V-Visual and visible light Y-Surveillance (search detect, and multiple target tracking) and control (both fire control and air control)  
  W-Armament (peculiar to armament, not otherwise covered)    
  X-Facsimile or television    
  Y-Data processing    

Figure 1-23. - Joint service classification system.


No single radar system has yet been designed that can perform all of the many radar functions required by the military. Some of the newer systems combine several functions that formerly required individual radar systems, but no single system can fulfill all the requirements of modern warfare. As a result, modern warships, aircraft, and shore stations usually have several radar systems, each performing a different function.

One radar system, called SEARCH RADAR, is designed to continuously scan a volume of space to provide initial detection of all targets. Search radar is almost always used to detect and determine the position of new targets for later use by TRACK RADAR. Track radar provides continuous range, bearing, and elevation data on one or more targets. Most of the radar systems used by the military are in one of these two categories, though the individual radar systems vary in design and capability.

Some radar systems are designed for specific functions that do not precisely fit into either of the above categories. The radar speed gun is an example of radar designed specifically to measure the speed of a target. The military uses much more complex radar systems that are adapted to detect only fast-moving targets such as aircraft. Since aircraft usually move much faster than weather or surface targets, velocity-sensitive radar can eliminate unwanted clutter from the radar indicator. Radar systems that detect and process only moving targets are called MOVING-TARGET INDICATORS (mti) and are usually combined with conventional search radar.

Another form of radar widely used in military and civilian aircraft is the RADAR ALTIMETER. Just as some surface-based radars can determine the height of a target, airborne radar can determine the distance from an aircraft to the ground. Many aircraft use radar to determine height above the ground. Radar altimeters usually use frequency-modulated signals of the type discussed earlier in the chapter.


The preceding paragraphs indicated that radar systems are divided into types based on the designed use. This section presents the general characteristics of several commonly used radar systems. Typical characteristics are discussed rather than the specific characteristics of any particular radar system.


Search radar, as previously mentioned, continuously scans a volume of space and provides initial detection of all targets within that space. Search radar systems are further divided into specific types, according to the type of object they are designed to detect. For example, surface-search, air-search, and height-finding radars are all types of search radar.

Surface-Search Radar

A surface-search radar system has two primary functions: (1) the detection and determination of accurate ranges and bearings of surface objects and low-flying aircraft and (2) the maintenance of a 360-degree search pattern for all objects within line-of-sight distance from the radar antenna.

The maximum range ability of surface-search radar is primarily limited by the radar horizon; therefore, higher frequencies are used to permit maximum reflection from small, reflecting areas, such as ship masthead structures and the periscopes of submarines. Narrow pulse widths are used to permit a high degree of range resolution at short ranges and to achieve greater range accuracy. High pulse-repetition rates are used to permit a maximum definition of detected objects. Medium peak power can be used to permit the detection of small objects at line-of-sight distances. Wide vertical-beam widths permit compensation for the pitch and roll of own ship and detection of low flying aircraft. Narrow horizontal-beam widths permit accurate bearing determination and good bearing resolution. For example, a common shipboard surface-search radar has the following design specifications:

  • Transmitter frequency 5,450-5,825 MHz
  • Pulse width .25 or 1.3 microseconds
  • Pulse-repetition rate between 625 and 650 pulses per second
  • Peak power between 190 and 285 kW
  • Vertical beam width between 12 and 16 degrees
  • Horizontal beam width 1.5 degrees

Surface-search radar is used to detect the presence of surface craft and low flying aircraft and to determine their presence. Shipboard surface-search radar provides this type of information as an input to the weapons system to assist in the engagement of hostile targets by fire-control radar. Shipboard surface-search radar is also used extensively as a navigational aid in coastal waters and in poor weather conditions. A typical surface-search radar antenna is shown in figure 1-24.

Figure 1-24. - Surface-search radar.

Q.32 What type of radar provides continuous range, bearing, and elevation data on an object? answer.gif (214 bytes)
Q.33 Radar altimeters use what type of transmission signal?answer.gif (214 bytes)
Q.34 A surface-search radar normally scans how many degrees of azimuth? answer.gif (214 bytes)
Q.35 What limits the maximum range of a surface-search radar? answer.gif (214 bytes)
Q.36 What is the shape of the beam of a surface-search radar? answer.gif (214 bytes)

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