Page:Electronics Technician - Volume 3 - Communications Systems - NAVEDTRA 14088.pdf/11

 CHAPTER 1

INTRODUCTION

Communications in general, and especially in systems, covers a broad spectrum, from a simple singlechannel voice circuit, to the fastest growing field of electronics—satellite communications. This training manual will provide you with knowledge applicable to questions and situations that arise on the job. Chapter 1 is a refresher course in basic communications systems and terminology. Chapters 2 and 3 will lead you through many of the systems and equipments in use today. Chapter 4 will discuss the Link-11 system, chapter 5 will cover the Link-11 Fault Isolation, chapter 6 will discuss Link 4-A, chapter 7 will introduce you to the new technology in data communications and the Link-16 system, and chapter 8 will discuss local-area networks.

The Electronics Technician rating is extremely diverse. Many ETs never get the opportunity to work in the communications field. Those who do are often locked into one particular system for many years. This assignment pattern sometimes causes ETs to feel overwhelmed or lost in their career. The massive amount of information ETs can be questioned on and expected to know can be frustrating. But the goal YOU and every ET must have is to become as knowledgeable as possible to be better. prepared for all future challenges.

After completing this chapter, you should be able to:
 * Identify the basic principles of rf communications
 * Recognize the basic equipment used for rf communications
 * Determine the frequency spectrum allocated to rf communications

RADIO COMMUNICATIONS

Navy ships, planes, and shore bases operate as a team working together to accomplish a specific task. Radio equipment is used to coordinate the activities of the many fleet units by linking them with each other and with shore stations.

Radio can be defined as the transmission and reception of electronic impulses or signals through space by means of electromagnetic waves. Usually, the term is used in referring to the transmission of intelligence code and sound signals, although television and radar also depend on electromagnetic waves.

At one time, the term radio communications brought to mind telegraphy (CW), voice (AM), and possibly teletype communications. Today’s radio communications has become a highly sophisticated field of electronics. You, the technician, need to become familiar with the diverse systems in use today.

The primary means of communicating between ships and between ships and stations is known as telecommunications. Telecommunications refers to communications over a distance and includes any transmission, emission, or reception of signals, writing, images, and sounds. Intelligence produced by visual or oral means or by wire, radio, or other electromagnetic systems is also included. Electrical, visual, and sound telecommunications are all used by the Navy. In this volume we will discuss electrical types of telecommunications.

COMMUNICATIONS SYSTEMS

A communications system consists of two or more units, each having its own separate identity, arranged and interconnected to perform a circuit operation that cannot be performed by one of the individual units alone. Navy communications systems vary from simple to very complex, depending upon the circuit operations involved. Each system requires the integrated use of various types of equipment, so flexibility is of the utmost importance. This flexibility is provided through a complex arrangement of interconnections that allow the physically separated sets, groups, and units to be selectively switched (patched) into the different circuit configurations. 1-1