Question

which of the following is correct for amplitude modulation ?

1)the amplitude of the carrier wave is modified but the frequancy remains fixed

2)the amplitude of the carrier wave remain unchanged but the frequency is modified

3)both the frequency and amplitude of the carrier wave change

4)the frequency and phase of the carrier wave change but the amplitude is unchanged

any one ​

Answer 1

When audio signals are transmitted over thousands of kilometres through radio transmission, the audio frequencies that lie within the frequency range of 15 Hertz to 20 KiloHertz has very small signal power and thus cannot be transmitted via the antenna for communication purposes. The radiation of electrical energy is only possible at frequencies above 20 KiloHertz. The main advantage of high-frequency signals is that they can be transmitted over very long distances by dissipating very small power.

Thus, the audio signals must be sent along with the high-frequency signals for communication. This can be done by superimposing electrical audio signals on a high-frequency wave called the carrier wave. The carrier wave is generated from radio-frequency oscillators and is undamped in nature. Thus, when the audio-frequency signal is superimposed on a carrier wave, the resulting wave gets all the