The Navy Electricity and Electronics TrainingSeries (NEETS) modules, especially module 18, RadarPrinciples, provide information that is basic to yourunderstanding of this volume. This volume will discussradar and radar systems as you may encounter them asan Electronics Technician at your command. Youshould refer to NEETS module 18 and ElectronicsInstallation and Maintenance Book (EIMB), Radar andElectronic Circuits, on a regular basis to ensure that youhave a complete understanding of the subject mattercovered in this volume.As an Electronics Technician, Second Class, andpossible work center supervisor, you must understandthe basic radar principles and safety requirements forradar maintenance. However, due to luck of the draw,your first assignment may not afford you exposure toradar systems. Our intention with this volume is NOTto teach you every radar system the Navy uses, butsimply to familiarize you with the radars and theirgeneral maintenance principles.You will be able to identify the equipmentrequirements and general operation of the three basicradar systems covered in chapter 1. You’ll becomefamiliar with the nomenclature of specific radars usedin the Navy today as we discuss them in chapter 2. Then,armed with all that knowledge you will easily grasp thesystem concepts addressed in chapter 3. And before yougo out to tackle the radar world, chapter 4 will give younecessary safety information specific to radarmaintenance.When you arrive at your next command as a secondclass with work center responsibilities for a radarmaintenance shop, you will be ready.
BASIC RADAR CONCEPTS
The term radar is an acronym made up of the wordsradio, detection, and ranging. It refers to electronicequipment that detects the presence, direction, height,and distance of objects by using reflectedelectromagnetic energy. The frequency ofelectromagnetic energy used for radar is unaffected bydarkness and also penetrates weather. This permitsradar systems to determine the position of ships, planes,and land masses that are invisible to the naked eyebecause of distance, darkness, or weather.Radar systems provide only a limited field of viewand require reference coordinate systems to define thepositions of the detected objects. Radar surface angularmeasurements are normally made in a clockwisedirection from TRUE NORTH, as shown in figure 1-1,or from the heading line of a ship or aircraft. The actualradar location is the center of this coordinate system.Figure 1-1 contains the basic terms that you need toknow to understand the coordinate system. Those termsare defined in the following paragraph.The surface of the earth is represented by animaginary flat plane, known as the HORIZONTALPLANE, which is tangent (or parallel) to the earth’ssurface at that location. All angles in the up directionare measured in a secondary imaginary plane, known asthe VERTICAL PLANE, which is perpendicular to thehorizontal plane. The line from the radar set directly tothe object is referred to as the LINE OF SIGHT (LOS).The length of this line is called RANGE


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