Figure 4. Block Diagram of Detector and RF Amplifier.
c. Audio frequency amplifier. The power output of a detector, with or without an RF amplifier,
is generally too little to be useful. One or more audio frequency amplifiers (figure 5), therefore, are
added to the receiver to increase the audio frequency power to a level that will operate headphones, a
loudspeaker, or teletypewriter equipment.
Figure 5. Block Diagram of Complete Radio Receiver.
Learning Event 2:
General. Radio waves travel near the surface of the earth and also radiate skyward at various
angles to the earth's surface (figure 6). These electromagnetic waves travel through space at the speed of
light, approximately 186,000 miles (300,000 kilometers (km)) per second.