comms topic no. 2

• Allocation


  Entry in the Table of Frequency Allocations of a given frequency band for the purpose of its use by one or more terrestrial or space radio communication services or the radio astronomy service under specified conditions
• Allotment


  Entry of a designated frequency channel in the agreed plan, adopted by the ITU, for use by one or more nations for a terrestrial or space radio communication services in one or more identified countries or geographic areas and under specified conditions
• Assignment


  Authorization given by a nation for a radio station to use a radio-frequency channel under specified conditions
• The electromagnetic spectrum illustrates the range of frequencies applicable to electronic communication
• Electromagnetic waves are signals that oscillate. It consists of electric field and magnetic field. It is also characterized by its amplitude, frequency or phase
• Frequency


  The number of times a particular phenomenon occurs in a given period of time expressed in Hertz
• Wavelength


  The distance between two points of similar cycles of a periodic wave or the distance traveled by an electromagnetic wave during the time of one cycle typically expressed in meters
• Period


  The time required for one complete cycle of a repetitive system, or simply the reciprocal of frequency
• Time Domain Representation


  A standard oscilloscope is used to display the amplitude versus time representation of the input signal
• Frequency Domain Representation


  A spectrum analyzer is used to display the amplitude versus frequency representation of the input signal
• Attenuation


  Type of transmission impairment in which the signal loses strength due to the resistance and length of the transmission medium
• Distortion


  The alteration of information in which the original proportions are changed, resulting from a defect in communication system
• Noise


  Type of transmission impairment in which an outside source such as crosstalk corrupts a signal
• λ - wavelength in meters
• c - speed of light (3x108)
• f - frequency in Hz
• narrowband - a single channel (64Kbps) or some number of 64Kbps channels (Nx64 Kbps), but less than wideband.
• wideband - is a multi-channel capacity that is between 1.544 Mbps

  and 45 Mbps according to U.S. standards (2.048 Mbps-34 Mbps

  according to European/international standards.)
• broadband - is a multi-channel capacity which is 45 Mbps according to U.S. standards and 34 Mbps according to European/international standards.
• distress - A mobile station in distress is in-need of immediate assistance.
• urgency - Radio messages with an urgency classification refer to a

  situation that requires immediate attention and might conceivably

  become distress in nature.
• safety - Radio communications with a safety classification refer to

  meteorological information, particularly about storms, hurricanes,

  etc.