Modulation is the process of varying some characteristic of a periodic wave with external signals. Modulation is utilized to send an information bearing signal over long distances. Radio communication superimposes this information bearing signal onto a carrier signal. These high frequency carrier signals can be transmitted over the air easily and are capable of traveling …
A heterodyne is a circuit that transfers a signal from one carrier wave to another with a different frequency. It mixes the input signal with a wave generated by an oscillator to create two new signals, called beats. While heterodyning is a simple process governed by the laws of trigonometry, most heterodynes are complex devices …
A spot beam is a beam of radio signals that is directed towards a specific area on the Earth’s surface. Spot beams are the opposite of broad beams, which are beams that are directed towards a large area of the Earth’s surface. While broad beams are used for general telecommunication and surveillance, spot beams are …
A projector lamp is used to transfer an image from a multimedia projector onto a larger screen. Earlier halogen bulbs were used for many years for projection purposes, but were discontinued as halogen produced a yellow tone on the images. A projector lamp relies on an intense light bulb, called a metal halide bulb, to …
Capacitive reactance is a term used to describe an effect in capacitors that causes the capacitor’s resistance to change depending on changes in the electric field passing through it. Capacitive reactance is similar to resistance in that it can allow or block varying amounts of voltage in a circuit, but is different because it is …
A spark-gap transmitter is a mechanism for producing radio signals. It has been the primary radio transmission device during the early years of radio technology. It was soon superseded by other transmitters due to its discontinuous radio wave production and widely varying frequencies. How a Spark-Grap Transmitter Works A spark gap transmitter is basically composed …
Four digit security codes protect Kenwood car stereos from theft. If a thief steals a Kenwood car stereo, he/she will not be able to use the stereo until the secret four digit security code is entered. Unfortunately, many legitimate owners are also locked out of their Kenwood car stereos due to these security codes. This …
A rheostat is an electrical component that has an adjustable resistance. It is a type of potentiometer that has two terminals instead of three. The two main types of rheostat are the rotary and slider. The symbol for a rheostat is a resistor symbol with an arrow diagonally across it. Rheostats are used in many …
Some materials have the ability to produce electricity when subjected to mechanical stress. This is called the piezoelectric effect. This stress can be caused by hitting or twisting the material just enough to deform its crystal lattice without fracturing it. The effect also works in the opposite way, with the material deforming slightly when a …
A MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is a device that switches or amplifies an electronic signal. MOSFET technology has made computers much smaller and more efficient than they once were by handling large amounts of electricity in very small spaces. MOSFETs are also crucial for both digital and analog signals and are found …