Radio Waves: A History, and Communication, Amplitude Modification (AM) and Frequency Modulation (FM)

The first forms of long-distance communication mediums were the telegraph (in 1837) and later the telephone in 1869). These inventions used wires to transmit noise from sender to receivers. The telegraph and telephone use vast networks of wires to send information.

Towards the end of the 19th century, much research was being done on the sending and receiving of signals without wires. The inventor of the radio is rooted in historical debate. Nikola Tesla unveiled the first wireless radio in 1893, however, credit for the invention is generally given to Guglielmo Marconi who obtained the patent in 1896. These first wireless radios relied on James Clark Maxwell's 1920 Theory of Electromagnetism to create a wireless connected between electricity and magnetism. Prior to WWI, these early radios were used nautically on ships and vessels for communication. Through the 1920's, the first broadcasting stations were developed including KDKA in Pittsburgh Pennsylvania and BBC in Britain. The introduction of radio stations commercialized the radio and it soon became a fixture in most homes. WWII was the first war to be covered by radio and the 1930's - 1940's is known as the Golden Age of Radio, where radio shows were the most popular form of entertainment in homes around the word. Radio and the technologies it relies on was further developed so that information such as sound (radio) and pictures (television) could be broadcast and received.

Radio waves are part of the electromagnetic spectrum. They are sent from transmitters and can travel in one of 3 ways, depending on their wavelength.

A barrier in the transmission of radio waves is diffraction. This is the apparent bending of waves around obstacles. This diffraction is influenced by the wavelength of the radio waves. A radio wave with a large wavelength is able to diffract around obstacles, whereas the smaller wavelengths will not. Look at the example below of the houses in the hills.

It is not able to receive short wavelength broadcasts, but can pick up the long ones.

Remember that the amplitude of a wave is its displacement from the normal, and frequency is how often the wave occurs. See properties of waves.

AM and FM are two ways that signals are represented in radio waves and you will recognize these terms being used if you listen to the radio. Here is a quick comparison of the two:

AM	FM
Noise affects the amplitude of a wave more readily so the signal can be of lower quality. Have a longer distance range.	Higher quality reception since noise doesn't affect frequency. Has a shorter range.

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Radio Waves: A History, and Communication, Amplitude Modification (AM) and Frequency Modulation (FM). (2019). In ScienceAid. Retrieved Apr 24, 2024, from https://scienceaid.net/physics/waves/radio.html

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