Chapter 9. Arduino-SNAP Circuit AM Radio

The superheterodyne (superhet) radio is considered to be the first receiver using AM for audio reception. Edwin Howard Armstrong, an inventor, is credited with the creation of many of the AM radio features known today. Edwin Armstrong patented three important functions that made the use of AM radio possible today: regeneration, the superhet circuit, and positive feedback. Regeneration allows an electronic signal, such as radio waves, to be amplified many times by the same active device, such as a transistor or operational amplifier. The superhet circuit can easily convert a received signal to a fixed intermediate frequency (IF), which can be more conveniently processed than the original radio carrier frequency. Finally, positive feedback increases the gain or amplification of radio waves by using a closed-loop amplifier circuit. An example of a superhet AM radio is shown in the following screenshot:

Note

Superhet is short form for superheterodyne. AC...