Do wireless signals (Wifi router, radio, telephone) send their information in single "blinks" or in a continuous wave with frequency modulation or Amplitude modulation?

If a radio for example needs to transmit only sound it would make sense to me that the electric field just oscillates with the right parameters just like the sound wave.

But for a computer, where information of all kind needs to be transmitted, it could also be possible that a router sends waves in single bursts and the receiver detects this burst as a 1 and a non existing one as a 0.

  • $\begingroup$ If by "radio" you mean the device that plays music in your car, then they transmit sound with speakers, not electric fields. The antenna in your car receives information from radio waves. If it's an FM(AM) station, then the information is encoded using frequency(amplitude) modulation. $\endgroup$ – honeste_vivere Aug 18 '17 at 13:36
  • $\begingroup$ Yes I always talk about EM Signals. FM(AM) = Modulation is somewhat clear. This implies a continuous wave, right? So what about my other idea, sending pulses of EM Wave for 0 and 1 encoding, does that happen somewhere? $\endgroup$ – D.Niermann Aug 18 '17 at 14:39
  • $\begingroup$ Look up topics on carrier waves. $\endgroup$ – honeste_vivere Aug 18 '17 at 14:41

What you seem to call "1-0 encoding" is usually referred to as On-Off keying, it can be done via radio waves and is done if you must use the simplest form of carrier wave modulation. I say carrier wave modulation because transmit/receive antennas do not work at dc, to be radiated you need a positive frequency. Direct carrier on-off keying belongs to the class of orthogonal keying and it is the least efficient, albeit the simplest form of it. By efficiency I mean the BER v. SNR curve. At microwaves it is also easier to phase or frequency modulate the carrier than amplitude modulating it. Well above 100GHz where phase coherent signals and their amplification are difficult to come by direct carrier modulation with on-off keying is still widely used as being the easiest thing to do.


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