Helpful Definitions

• Amplifier
  A device for obtaining an increase in voltage, current, or power.
   
• Amplitude
  The maximum departure of the value of an alternating current or radio wave from the average value.
   
• Analog
  A signal that may vary continuously over a specific range of values.
   
• Antenna
  A device for radiating or receiving radio waves.
   
• Band
  A well-defined range of wavelengths or frequencies.
   
• Bandwidth
  The range within a band of frequencies.  A measure of the amount of information that can flow through a given point at any given time.
   
• Bit
  Abbreviation for binary digit (either 0 or 1), the basic unit for storing data in a computer.
   
• Cavity Filter
  A device used to shield the receiver from the transmitter and to form a circuit called a duplexer.
   
• Channel
  A band of frequencies of sufficient width to allow a single radio communication.
   
• Combiner
  A device used to combine the output signals from a number of transmitters connected to the same antenna (in a trunked system).
   
• Coverage  
  The amount or percentage of area reached by a communications medium.
   
• Cycle
  One complete performance of a vibration, electrical oscillation, current alternation, or other periodic process.
   
• Digital
  Information that can be represented by two discrete states (either 0 or 1).  Most information in the speaking/seeing world is not digital, but must be converted into this form to be used by computers.
   
• Dipole
  A radio antenna consisting of two horizontal rods in line with each other, with their ends slightly separated.
   
• Duplexer
  A switching device that allows alternate transmission and reception with the same radio antenna.
   
• Effective Radiated Power
  A term for describing radio power levels.
   
• Frequency
  The number or repetitions of a periodic process in a unit of time.
   
• Frequency multiplier
  A device multiplying the frequency up to a desired output frequency.
   
• Gain
  The effectiveness of a directional antenna express as the ratio in decibels of standard antenna input power to the directional antenna input power that will produce the same field strength in the desired direction.
   
• Guard Band
  A non-overlapping space between radio channels used to minimize interference.
   
• Hertz
  Abbreviation for cycles per second.
   
• Interference
  Confusion of received radio signals due to strays or undesired signals.
   
• Isolator
  A device that may be added to the circuit between each transmitter and the combiner and used to increase the isolation to the other transmitter outputs.
   
• Isotropic radiator
  A theoretical antenna that radiates equally in all directions.
   
• Loop Protected
  Method of protection of baseband. A break in the main route causes loop switches to operate thus rerouting the upper 300 multiplex channels. The lower 300 channels will stop at the break.
   
• Loop Switch
  Device used to break baseband on a backbone radio.
   
• Microwave
  Radio frequencies of extremely short wavelength.
   
• Modem
  An acronym for modulator/demodulator, which is a device that translates digital signals coming from your computer into analog signals that can be transmitted over standard telephone lines.  The modem also translates the analog signal back into a digital signal that your computer can understand.
   
• Modulation
  The process of varying the amplitude, frequency, or phase of a carrier or signal in telephone, radio, or television.
   
• Monitored Hot Standby
  In 2 GHz radios, it is a method of redundant operation for transmitters and receivers. The failed unit is switched offline and the standby unit is placed into service.
   
• Multicoupler
  A device used to connect a multitude of receivers to a single antenna.
   
• Multiplex
  The channels to which customer equipment is connected to enable communication via microwave.
   
• Mute Point
  This is the condition that exists when the RF signal to a receiver has degraded to a such a degree that it produces excessive noise. The muting circuitry then silences the receiver. Similar to the squelch on a two-way radio.
   
• MTU
  Master Terminal Unit. The computer at site 1 that polls the field units (RTUs).
   
• Noise
  An unwanted signal or disturbance (e.g., static) in a radio communications system.
   
• OLP
  Stands for On Line Protection which is a method of transmitter redundancy. Unlike hot standby, with this method both transmitters are online at the same time with combined outputs. When one fails, the other continues with reduced power.
   
• Omnidirectional 
  Receiving or sending waves equally well in all directions.
   
• Orderwire
  An intercom-like device for talking site to site within an orderwire segment or directly to site 1 at Frankfort.
   
• Oscillator
  A device for producing alternating current, specifically for producing radio frequencies.
   
• Path Fade
  The attenuation of the signal from a transmitter to a receiver due to rain or atmospheric conditions.
   
• Polarization
  The action or process of affecting radiation so that the vibrations of the wave assume a definite form.
   
• Power Plant
  The 12 and  24 volt chargers and batteries in a microwave site.
   
• Propagation
  The action of traveling and spreading through space, in reference to wave energy.
   
• Radio Pilot
  A signal of a specific frequency to indicate per hop continuity.
   
• Receiver
  The portion of a radio device that converts the radio waves into audible signals.
   
• Rectifier
  Refers to one of the chargers in a microwave site. A somewhat inaccurate term, but is common in the industry.
   
• Refarming
  An administrative process being conducted by the FCC to reduce channel bandwidths and, as a result, promote spectrum efficiency.
   
• Repeater
  A transmitter and a receiver operating on different frequencies and often connected to a common antenna.
   
  RTU
  Remote Terminal Unit. This is the unit in the sites that reports the alarm status.
   
• Signaling
  A method of remote controlling objects via a multiplex channel. Such as ringing a phone or turning things on or off.
   
• Skip
  The phenomenon by which a radio wave reflects from the ionosphere during the height of the sunspot cycle, often resulting in severe interference problems.
   
• Spectrum
  The region of the electromagnetic spectrum in which radio transmission and detection techniques may be used.
   
• Spectrum Efficiency
  The ability to optimize the amount of information sent through a given amount of bandwidth.
   
• Spur
  Typically refers to a 2 GHz route that branches off of the main routes.
   
• Transmitter
  The portion of the radio device that sends out a radio signal.
   
• Transmission Line
  The cable from the radio to the antenna. It may be either waveguide or coaxial cable.
   
• Vocoder
  Abbreviation for voice coder, a circuit that samples a voice frequency and then changes the sampled information into binary digits to modulate the carrier.
   
• VF
  Stands for “voice frequency”. One of the lowest frequency components of the baseband. It is also the customer interface to a channel unit.