Section 3
Transmitters and Receivers

Demodulation

3K1 Recall that the detector/demodulator stage recovers the original information from the modulated signal.

The Detection / Demodulation stage recovers the original modulated signal. The detection / demodulation stage of the receiver would need to be correctly set to the mode being received, CW, AM, USB, LSB, FM, RTTY etc so that the signal would be correctly detected.

So we understand that the previous stage can tune and amplify an RF signal, next we need a section that can recover the original modulating signal or DETECT the signal.

Let's put that another way. You may recall that in a transmitter the audio signal ;was changing the RF signal or as it is called modulating the signal so detection is to recover this original audio signal.

You may be able to remember detection by thinking of a policemen who is a detective and the graphic below !

Recall that the audio amplifier ensures the recovered modulation is strong enough to drive headphones or a loudspeaker.

The signal even when detected is still to small to hear so as with a CD player or tape deck the signal is sent to an Audio amplifier and then delivered so that you can hear it to a speaker of ear piece / head phones.

The origin of some of the text on this page is from the RSGB with additions by the web master