Radio, in which parameter is the information?

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Discussion Overview

The discussion centers around the parameters in which information is encoded in radio signals, specifically exploring the roles of amplitude and frequency in the transmission of audio content such as songs and news. The scope includes technical explanations of modulation techniques and the characteristics of radio waves.

Discussion Character

  • Technical explanation, Debate/contested

Main Points Raised

  • One participant asserts that information cannot be in amplitude due to its decrease with distance, suggesting that the data received is relatively identical.
  • Another participant counters that information can indeed be encoded in amplitude or frequency, referencing relative amplitudes and small variations in frequency as potential carriers of information.
  • A participant notes that while frequency is constant for each channel, FM channels in the USA actually span a frequency range, which may allow for variations in the signal.
  • One participant explains that AM (amplitude modulation) and FM (frequency modulation) involve modulating the carrier wave to transmit audio signals within the human hearing range.

Areas of Agreement / Disagreement

Participants express differing views on whether information is encoded in amplitude or frequency, indicating that multiple competing perspectives remain unresolved.

Contextual Notes

Some claims depend on specific definitions of modulation and the characteristics of radio waves, which may not be universally agreed upon. There are also references to external sources that may contain additional context or corrections.

Helicobacter
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When I listen to radio, then I know that the radio gets the information from electromagnetic radio waves. But in which parameter is the information of the song/news/output/whatever included?

It can't be amplitude, since amplitude decreases with distance of obstruction, and the data most people receive is relatively identical.

it can't be frequency/wavelength, since every channel has a constant frequency assigned to.
 
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Helicobacter said:
it can't be frequency/wavelength, since every channel has a constant frequency assigned to.

In the USA, each FM channel actually spans a frequency range of 0.2 MHz. For example, a station that broadcasts at 90.1 MHz actually uses frequencies between 90.0 and 90.2 MHz.

http://www.fcc.gov/mb/audio/bickel/oddno.html

The diagram on that page has a typographical error. FM Channel 202 should be labeled as 88.3 MHz.
 
Last edited by a moderator:
AM = amplitude modulation
FM = frequency modulation

Remember that the radio freq is a carrier wave. This means that the (AM)680kHz wave or (FM)107.1 MHz wave is modulated to provide a much lower normal humans range signal riding on top.

FM = the frequency of the carrier is modulated to carry sounds in the normal human range
AM = the amplitude of the carrier is modulated to carry sounds in the normal human range
 

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