High level basics about Audio Tuners

Many people enjoy listening to the radio. They do so either in their car or at home. And even now over the internet. 

An audio tuner is what makes that possible. Typically for the home (or business) these tuners pick up either AM or FM waves from the broadcaster. An internal processor interprets these waves, converts them to a signal which is eventually sent to the speakers and reproduced as the sound you hear coming from either your speakers or head phones. 

In technical terms - A tuner is a circuit module or free-standing equipment which detects radio-frequency (RF) signals usually of low amplitude and amplifies them and converts them to a form suitable for further processing. The signals being detected are usually electromagnetic waves 

Traditionally there were:

• AM - Low band uses amplitude modulation (0.300 MHz to 3 MHz)
  
• FM – High Band uses frequency modulation (30 MHz to 300 MHz)  
  

With the advent of satellites and digital technology – new bands and hence new receivers were developed these use 2.3 GHz S band (2.310 to 2.360 GHz) in the US companies like Sirius XM Radio use this. 

Trivia:

As of August 2007, the FCC (Federal Communications Commission) had licensed 4779 AM stations and 9159 FM stations (6279 commercial and 2880 educational).