TABLE OF CONTENTS Communication signals are also important to EW considerations. They are intercepted and jammed, and their externals are analyzed to determine an enemy's electronic order of battle. The messages carried by a communication system are called the signal internals, while the modulation, transmitter location, and so forth are called its externals.
While radar signals are typically transmitted from narrow-beam antennas, communication signals are usually transmitted from antennas that cover 360 degrees of azimuth. Also, since communication signals are designed to carry information, they tend to have high duty factor (with notable exceptions, such as burst transmissions) and to use continuous type modulations.
As shown in Figure 2.19, communication involves one-way links. Each link includes a transmitter, a transmitting antenna, a receiving antenna, a receiver, and everything that happens to the signal in between. The purpose of the communication link is to get information from the location of the transmitter to the location of the receiver. Equations to predict the performance of one-way links will be covered in Chapter 4.
The most significant type of communications signals for EW consideration support tactical communication associated with military organizations. Tactical radios are normally transceivers (i.e., they transmit and receive through one antenna). They are typically organized into nets, as shown in Figure 2.20. All of the radios in a net typically operate on a single frequency, so only one member of the net can transmit at a time. In a military organization, the...
