Question

Why is amplitude modulation used for long distance communication?

Answer 1

Let us first get some idea about modulation. Modulation is the process of changing one or more features of a periodic waveform, called the carrier signal, with a second signal, called the modulation signal, which often carries information to be transferred in electronics and telecommunications.

Complete step-by-step solution:
The modulation signal could be an audio signal from a microphone, a video signal from a video camera, or a digital signal from a computer that represents a sequence of binary digits, known as a bitstream. The modulation signal has a lower frequency than the carrier. The goal of modulation is to imprint information on the carrier wave, which then transports it to a different destination. The modulated carrier is broadcast through space as a radio wave to a radio receiver in radio communication.
Amplitude modulation (AM) is a modulation technique used in electronic communication, most notably for radio wave transmission of messages. The amplitude (signal strength) of the carrier wave is altered in proportion to that of the message signal, such as an audio signal, in amplitude modulation. In contrast to angle modulation, which changes the carrier wave's frequency or phase, as in frequency modulation or phase modulation.
Amplitude modulation (AM) signals are simple to demodulate, and radio receivers are capable of doing so. Because AM signals are less sophisticated and more cost-effective, they are employed for long-distance transmission.

Note: The receiver amplifies and detects noise and electromagnetic interference in identical proportion to the signal, which is a shortcoming of all amplitude modulation systems, not just standard AM. Increasing the received signal-to-noise ratio by a factor of ten (a ten-decibel improvement) would necessitate a ten-fold increase in transmitter power.