Answers (1) |
sumesh kumar
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Jan 26, 2006,11:02 am
There are several difficulties in the propagation of electromagnetic (EM) waves at audio frequencies below 20 kHz (without modulation). For efficient radiation and reception the transmitting and receiving antennas would have lengths equal to the quarter wavelength of frequency used. This is 75 meters at 1 MHz. A vertical antenna of this size is impracticable.
<br>Also if the signals are transmitted without modulation, the signals from different sources will mix up. To avoid these, we use modulation.
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