© 2008 The McGraw-Hill Companies
9-1: Basic Principles of Signal Reproduction
In radio communication systems, the transmitted signal is very weak when it reaches the receiver, particularly when it has traveled over a long distance.
The signal has also picked up noise of various kinds.
Receivers must provide the sensitivity and selectivity that permit full recovery of the original signal.
The radio receiver best suited to this task is known as the superheterodyne receiver.