For example, in AM radio communication, a continuous wave radio-frequency signal has its amplitude modulated by an audio waveform before transmission. The message signal determines the envelope of the transmitted waveform. In the frequency domain, amplitude modulation produces a signal with power concentrated at the carrier frequency and two adjacent sidebands. Each sideband is equal in bandwidth to that of the modulating signal, and is a mirror image of the other. Standard AM is thus sometimes called "double-sideband amplitude modulation" (DSBAM). In 1982, the International Telecommunication Union (ITU) designated the types of amplitude modulation: Figure 4: Modulation depth. In the diagram, the unmodulated carrier has an amplitude of 1. Modulation methods [ edit ] Anode (plate) modulation. A tetrode's plate and screen grid voltage is modulated via an audio transformer. The resistor R1 sets the grid bias; both the input and output are tuned circuits with inductive coupling. m = p e a k v a l u e o f m ( t ) A = M A {\displaystyle m={\frac {\mathrm {peak\ value\ of\ } m(t)}{A}}={\frac {M}{A}}} Jagadamma, S. & Lal, R. Distribution of organic carbon in physical fractions of soils as affected by agricultural management. Biol. Fert. Soils 46, 543–554, https://doi.org/10.1007/s00374-010-0459-7 (2010).

Blanco-Canqui, H. & Lal, R. Tensile strength of aggregates. In (Ed. Lal, R.) Encyclopaedia of Soil Sciences, (Marcel Dekker, New York, 2004). In this simple case m is identical to the modulation index, discussed below. With m = 0.5 the amplitude modulated signal y( t) thus corresponds to the top graph (labelled "50% Modulation") in figure 4.

AT&T, Telecommunication Transmission Engineering, Volume 1— Principles, 2nd Edition, Bell Center for Technical Education (1977) Antil, R. S., Gerzabek, M. H., Haberhauer, G. & Eder, G. Long-term effects of cropped vs. fallow and fertilizer amendments on soil organic matter I. Organic carbon. J. Plant Nutr. Soil Sci. 168, 108–116, https://doi.org/10.1002/jpin.200421461 (2005). y ( t ) = [ 1 + m ( t ) A ] c ( t ) = [ 1 + m cos ⁡ ( 2 π f m t + ϕ ) ] A sin ⁡ ( 2 π f c t ) {\displaystyle {\begin{aligned}y(t)&=\left[1+{\frac {m(t)}{A}}\right]c(t)\\&=\left[1+m\cos \left(2\pi f_{m}t+\phi \right)\right]A\sin \left(2\pi f_{c}t\right)\end{aligned}}} The simplest form of AM demodulator consists of a diode which is configured to act as envelope detector. Another type of demodulator, the product detector, can provide better-quality demodulation with additional circuit complexity.

García-Oliva, F., Casar, I., Morales, P. & Maass, J. M. Forest-to-pasture conversion influences on soil organic carbon dynamics in a tropical deciduous forest. Oecologia 99, 392–396, https://doi.org/10.1007/BF00627754 (1994). In 1915, John Renshaw Carson formulated the first mathematical description of amplitude modulation, showing that a signal and carrier frequency combined in a nonlinear device creates a sideband on both sides of the carrier frequency. Passing the modulated signal through another nonlinear device can extract the original baseband signal. [4] His analysis also showed that only one sideband was necessary to transmit the audio signal, and Carson patented single-sideband modulation (SSB) on 1 December 1915. [4] This advanced variant of amplitude modulation was adopted by AT&T for longwave transatlantic telephone service beginning 7 January 1927. After WW-II, it was developed for military aircraft communication. At the same time as AM radio began, telephone companies such as AT&T were developing the other large application for AM: sending multiple telephone calls through a single wire by modulating them on separate carrier frequencies, called frequency division multiplexing. [4] Single-sideband [ edit ] Fessenden was a significant figure in the development of AM radio. He was one of the first researchers to realize, from experiments like the above, that the existing technology for producing radio waves, the spark transmitter, was not usable for amplitude modulation, and that a new kind of transmitter, one that produced sinusoidal continuous waves, was needed. This was a radical idea at the time, because experts believed the impulsive spark was necessary to produce radio frequency waves, and Fessenden was ridiculed. He invented and helped develop one of the first continuous wave transmitters – the Alexanderson alternator, with which he made what is considered the first AM public entertainment broadcast on Christmas Eve, 1906. He also discovered the principle on which AM is based, heterodyning, and invented one of the first detectors able to rectify and receive AM, the electrolytic detector or "liquid baretter", in 1902. Other radio detectors invented for wireless telegraphy, such as the Fleming valve (1904) and the crystal detector (1906) also proved able to rectify AM signals, so the technological hurdle was generating AM waves; receiving them was not a problem. AM remains in use in many forms of communication in addition to AM broadcasting: shortwave radio, amateur radio, two-way radios, VHF aircraft radio, citizens band radio, and in computer modems in the form of QAM.The modulating message signal may be analog in nature, or it may be a digital signal, in which case the technique is generally called amplitude-shift keying. There may be a price to pay other than the price itself, though. As for the price, yes, it is a fair amount more expensive than the others, but in this case, you get what you pay for. Additionally, if one factors-in how many wraps / rods can be built from one kit, it is doubtful CC will cost 50 cents more per rod, an extremely small price to pay a superior product. There are two factors which may be unappealing to some though; 1.) The thin viscosity may require an additional coat, possibly even two, if a deep, high build coating is desired, 2.) With the extended pot life also comes an extended cure time. Personally, these two issues are of little concern to me but I can appreciate others’ priorities may be different. CrystalCoat consists of Portland cement, specially treated quartz and a compound of active chemicals, and is supplied in powdered form. It is either sprinkled onto fresh concrete or is mixed with water as a carrier and applied by means of brush or spray as a slurry for application to fully cured or older concrete or vertical surfaces.