Music and Voices: A Complete Guide to Amplitude Modulation

Amplitude modulation (AM), a technique used to transmit information through a radio carrier wave, uses varying strengths of transmission to its receptor, such as the specific loudspeaker sound waves or television pixel light waves. AM radio broadcasting, an earlier form of transmission technology, uses a receiver to detect the radio wave's amplitude variations and then amplifies the signal voltage changes to power the loudspeaker or earphones. Ham radio or amateur radio broadcasting delegates the private use of assigned radio bands through a noncommercial exchange of messages. Ham radio operators must communicate under certain constraints, mostly restrictions placed on public broadcasting by national regulatory agencies.

Amplitude Modulation: Forms and Designs

Amplitude modulation comes in many different forms and designs, such as commercial amplitude modulation, double side band suppressed carrier (DSB-SC) and single side band (SSB). Commercial amplitude modulation consists of a side band or a set of frequencies higher or lower than the carrier wave. A transmission is achieved by adding a DC offset to the base radio band signal (m)t and then multiplying a sinusoidal and frequency fc. A double side band suppressed carrier (DSB-SC) has the carrier frequency, usually in sinusoidal waveform, removed. In single side band modulation, only the upper or lower side bands are transmitted, which essentially means it only requires half of the bandwidth of amplitude modulation.

Commercial Amplitude Modulation Formula

Double Side band Suppressed Carrier Modulation Formula

Single Side band Modulation Formula

Amplitude Modulation Principles

There are specific mathematical principles applied to the amplitude modulation process. For instance, time domain, a term that describes the analysis of mathematical functions in respect to time, applies to all real numbers in regards to continuous time and discrete time. A frequency domain describes the analysis of mathematical functions or signals in respect to frequency, instead of time. Also, demodulation refers to extracting the informational signal from a modulated carrier wave. Demodulation requires a demodulator, a computer program or electronic component, to complete the process. The modulation index defines the measure of extended amplitude from an un-modulated carrier. This is important because is also describes a ratio of amplitude to tone for the audio signal. These factors then determine the number and spacing of the side frequencies of the transmitted signal.

Frequency Domain Applied to Amplitude Modulation

Time Domain Applied to Amplitude Modulation of Seismic Signals

Sinusoidal Amplitude Modulation

Amateur/Ham Radio

Amateur or ham radio uses privately designated radio bands under certain regulations, such as license and broadcasting restrictions. Ham operators come from all walks of life, including movie stars, students, truck drivers and normal, everyday people. Guglielmo Marconi, an Italian experimenter, was the first to transmit the letter "s" using Morse Code from Newfoundland to England in 1901, which sparked an onset of amateur radio enthusiasts. The U.S. established its first ham radio regulations in 1912 before the FCC was created in 1927. Amateur radio acquired the name "ham" because of the performance done over the band radios, which was referred to as "hamming it up." Ham radio operators have exploded recently because of its security to privately communicate two-way.

What is Amateur/Ham Radio?

A History of Early Ham Radio

Ham Radio and Radio Astronomy