Radio waves


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A slideshow on my research of radiowaves

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Radio waves

  1. 1. Radio Waves By Sam Wallis
  2. 2. What are radio waves? • Radio waves are a type of electromagnetic radiation, they have wavelengths in the electromagnetic spectrum. • Radio waves frequencies varies from 300 GMz to as small as 3 KHz. • Radio wavelengths varies from 1 millimetre long to 100 kilometres long. • Radio waves travel at the speed of light. • Radio waves have different frequencies when in the earths atmosphere, long wave lengths cover a part of the earth constantly and reflect off the ionosphere and then travel around the world. • Shorter wavelengths bend very little and travel on a line of sight meaning that if there are buildings etc. in the way then then the signal could be badly effected.
  3. 3. The use of radio waves Radio waves are mainly used for communication for devices such as: •Radio – For both FM and AM radio broadcasts •Television •Military communications •Mobile Phones •Wireless computer networks But also…. •Microwaves •Speed Cameras
  4. 4. Difference between AM and FM radio waves • AM stands for amplitude modulation. The signal for AM increases and decreases as the base signal changes. • AM radio signals will travel great distances so a single transmitter can cover large areas. • There cant be too many AM radio signals in one area as the signals will overlap one another • FM stands for Frequency Modulation, where the frequency of the carrier signal increases and decreases to represent the change in voltage of the base signal. • FM signals are known to offer better signal quality than AM but the range is far less. • Due to the range being far worse multiple transmitters are needed cover the same area as one AM transmitter would.
  5. 5. Wireless communication • Wireless communication devices such as radios, mobile phones, walky-talky's and Bluetooth headsets all use radio waves. The various available technologies differ in local availability, coverage range and performance. They three main ones are: • Wi-Fi – It is a wireless local area network that enables portable computing devices to connect easily to the Internet. • Cellular data service – This offers effective coverage within a range of 10-15 miles from the nearest cell site. • Mobile Satellite Communications- This may be used where other wireless connections are unavailable, such as in largely rural areasor remote locations. This is what the police force and the army use as it works on satellite communication.
  6. 6. Mobile computing • Mobile phones use the lowest power available radio waves, or radio frequency electromagnetic fields, to exchange information with the mobile network. • The radio wave exposure limits that apply to mobile phones are expressed in SAR (Specific Absorption Rate) levels and therefore it isn't proven that radio waves are dangerous for human health. • Mobile phones get radio waves from a local base station. Each base station can only serve a limited number of mobile phones at a time. • If the number of people using mobile phones keeps increasing it will mean that more base stations are needed.
  7. 7. Electromagnetic Spectrum • The electromagnetic spectrum is the range of all the possible frequencies of electromagnetic radiation. The electromagnetic spectrum of an object is the distribution of electromagnetic radiation emitted or absorbed by a particular object. • The electromagnetic spectrum is everything from low frequencies used for modern radio communication to even gamma radiation which is very high frequency. • Radio waves can be made to carry information by varying a combination of the amplitude, frequency, and phase of the wave within a frequency band. • The limit for long wavelength is the size of the universe as there is no limit.
  8. 8. Microwaves • Microwaves are radio waves with wavelengths ranging from as Long as one metre to as short as one millimetre • Alternatively with frequencies between 300 MHz (0.3 GHz) and 300 GHz. • Microwaves are at the higher frequency end of the radio wave band and low frequency radio waves are at the lower frequency end.