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Satellite communication
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Radios are the most common wireless item in existence and are in most homes. We use them for entertainment, communication, as an information source, or even just back ground noise. For many of us radios are almost a necessity, but how much do we know about how they function?
Antennas are one of the key pieces to a radio. Antennas come in a variety of shapes and sizes; they vary from large arrays to a small wire. Much of this variance is based on the broad use of radio waves and practicality; for instance you wouldn't use an antenna from a small radio to send a signal to a satellite.
Antennas work by creating a resonating flow of charge along its element. The resonance is caused by a magnetic field fluctuating through an inductor that is fixed to a capacitor. As a magnetic field fluctuates across a conductor it causes charges to move. This motion causes an electro magnetic wave.
The relations between the electricity and magnetism are explained by Maxwell's equations. Maxwell's equations are four equations that relate magnetic fields electric fields and charges and current.
A radio wave is an electro magnetic wave. We modulate them using three different modulations, frequency modulation, amplitude modulation, and pulse modulation, to carry information.
For frequency modulation slight variances are made in the frequency of the wave to represent different bits of information. This is widely used because it is less likely to have static.
For amplitude modulation the height or amplitude of the wave is changed to contain information. Amplitude modulation is not only used by radio stations but it is also used to send the picture part of television.
Pulse modulation is where there are breaks in the wave to indicate the desired information. This is usually used for morse code but can be used for a few other things as well.
According to maxwell's equations radio waves travel at the speed of light. The magnitude of a wave will decrease at a rate of r^2. Where r is the distance from the origin. This is because the wave is propagates in all directions so the same amount of energy spreads out over a greater area.
But how can we get signals from beyond the horizon? Today we could use satellites, but you can also bounce a radio wave off of parts of the upper atmosphere. This can be done because the sun ionizes levels of upper atmosphere.
Radios in the book show power in many different forms, whether it be propaganda, the ability to know of the outside world or just owning a radio, sets one higher than those without.
The level of RF a person receives is related to many factors, not only the placement of the antenna. Factors that can increase the level of RF are the number of “cells”, the distance to the “base station”, or the obstacles between the caller and the station. The number of cell zones depends on the user population. Heavily populated areas have more cells allowing for more telecommunication traffic. Being close to a cell site lowers the power needed to sustain a call, hence reduces the exposure to RF.
In an electromagnetic wave, the constantly changing electric and magnetic fields affect each other so they both oscillate in different axis while the wave moves in a direction perpendicular to the oscillation of the fields as shown in Figure 1.
A conductive atom’s valance shell is not completely full; electrons will flow from atom to atom because of this. When these electrons move from one atom to another, that is electrical current (a brief description of that is). A magnet can be made from different materials, but a loadstone is the natural form. The most important part of magnetism to make electric motors work is: A magnet has two different ends, or poles, a north and a south pole. These poles behave like electric charges, like poles repel and unlike poles attract although magnets have no effect on still charges.
Electromagnetic energy can be explained by treating the spread of energy over a range of wavelengths. The radiation can be measured by finding the energy falling per second that is Watts per square meter for each band of 1 micrometer wavelength.
When a ray of light is bounced or reflected off of a plane surface, there is a specific law that can be used to predict the angle at which it is reflected off of the surface. This is known as the ‘Law of Reflection’ and it states:
Synchronous Transmission: The synchronous signaling methods use 2 different signals. A pulse on one signal indicates when another bit of information is ready on the other signal. This is high speed data communication.
The phenomenon called electromagnetic induction was first noticed and investigated by Michael Faraday, in 1831. Electromagnetic induction is the production of an electromotive force (emf) in a conductor as a result of a changing magnetic field about the conductor and is a very important concept. Faraday discovered that, whenever the magnetic field about an electromagnet was made to grow and collapse by closing and opening the electric circuit of which it was a part, an electric current could be detected in a separate conductor nearby. Faraday also investigated the possibility that a current could be produced by a magnetic field being placed near a coiled wire. Just placing the magnet near the wire could not produce a current. Faraday discovered that a current could be produced in this situation only if the magnet had some velocity. The magnet could be moved in either a positive or negative direction but had to be in motion to produce any current in the wire. The current in the coil is called an induced current, because the current is brought about (or “induced”) by a changing magnetic field (Cutnell and Johnson 705). The induced current is sustained by an emf. Since a source of emf is always needed to produce a current, the coil itself behaves as if it were a source of emf. The emf is known as an induced emf. Thus, a changing magnetic field induces an emf in the coil, and the emf leads to an induced current (705). He also found that moving a conductor near a stationary permanent magnet caused a current to flow in the wire as long as it was moving as in the magnet and coiled wire set-up.
Electromagnetic radiation is energy that flows through free space. Electromagnetic radiation comes in a list of energies known as the electromagnetic spectrum. Electromagnetic spectrum is the complete range of the different wavelength of electromagnetic radiation. It consists of light, radio waves, visible light, infrared waves, ultraviolet light, x-rays, microwaves and gamma rays.
A cell phone is essentially a two-way radio consisting of a radio transmitter and a radio receiver. When you talk to your friend on your mobile phone, your mobile transfers your voice into an electrical signal, which is then transmitted through radio waves to the nearest cell tower. The network of cell phone towers then replays the radio wave to friend’s cell phone, which converts it to an electrical signal and back to sound. Cell phones transmit radio waves in all directions.
Faraday built two devices to produce what he called electromagnetic rotation: that is a continuous circular motion from the circular magnetic force around a wire. Ten years later, in 1831, he began his great series of experiments in which he discovered electromagnetic induction. These experiments form the basis of modern electromagnetic technology.
RADIO WAVES: Radio waves are used exactly for what it says — radio. They are also the waves responsible for the signals cell phones and televisions receive. Objects in space, such as planets and comets, giant clouds of gas and dust, and stars and galaxies, emit radio waves.
Radio broadcasting was introduced to the public in the early 1920s (Potter 226). There was only one type of broadcast protocol in the 1920’s and 30’s being AM radio(The Early Years). In 1921 there were only five AM radio stations, and only about 1% of all households in this country had a receiver (Potter 226). A receiver was basically another name for a radio because at this time radios were very expensive and there were not enough radio stations to make the system work. However, in 1923 there were over 500 stations to pop up which in turn led to increased sales of receivers to the general public (Potter 226). With the popping up of more radio stations the more receivers were being bought which meant that many people in the public were tuning into these various radio stations for information and entertainment. Radio was on the rise and it seemed that there was nothing slowing it down.
The electromagnetic spectrum can be determined by three different parts: theory of visible light, the ranges of the electromagnetic spectrum, and how it benefits mankind. There are many benefits to the electromagnetic spectrum such as heating up food or airport security scanners. Scientist and astronomers are now able to detect radio waves in the universe and place satellites in the galaxy. With new inventions using the electromagnetic spectrum, people can learn more about God's universe. People depend on this energy every day, whether it's on the radio or at a doctor's