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Thursday, November 30, 2017

Frequency Spectrum


Band
Range
Uses
Very Low Frequency(VLF)
3KHz-30KHz
Long range Radio Navigation
 Low Frequency(LF)
30KHz-300KHz
Radio Beacons
Medium Frequency(MF)
300KHz-3MHz
AM Radio
High  Frequency(HF)
3MHz-30MHz
Citizen Band(CB)/Ship/Aircraft Communication
Very High Frequency(VHF)
30MHz-300MHz
VHF TV, FM Radio
Ultra High Frequency(UHF)
300MHz-3GHz
UHF TV, Cellular phones
 Extremely High Frequency(EHF)
3GHz-30GHz
Satellite communication
Superior High Frequency(SHF)
30-GHz-300GHz
Radar, Satellite

Wireless Media



  It is also known as a wireless media. Wireless media transmit and receive electromagnetic signals without and electrical or optical conductor.  Here transmission and reception achieved by means of an antenna. For transmission antenna emits signal into medium and for reception antenna picks up electromagnetic signals from the surrounding medium. The two forms of transmission:
  Directional: - In this, transmitting antenna puts out a focused electromagnetic beam. The transmitting receiving antenna must be aligned, known as Point-to-Point Communication.
   Omni-directional: - In this the transmitted signal spreads out in all direction and be received by many antenna inspite of direction.
According to frequency range the wireless media is divided into three parts:-
·         Radiowave (30MHz-1GHz): Omni directional transmission
·         Microwave (1-40GHz): Point-to-Point Communication
·         Infrared (100GHz-1000 THz light frequencies): Local Point to Point, Multipoint application within confined areas.

Cable Transmission Media Comparison



Cable Transmission Media Comparison

Media
Cost
Ease of Installation
Capacity Range
Attenuation
Immunity from Interference
Unshielded Twisted Pair
Extremely Low
Very simple
1 to 100 Mbps
High, maximum effective range in 100s of meters
Low
Shielded Twisted Pair
Moderate
Simple to moderate
1 to 155 Mbps
High, maximum effective range in 100s of meters
Moderately low
Coaxial cable
Low to moderate
Simple
Varies by size and composition between 1 Mbps to Gbps
High, maximum effective range in low Kms
Moderate
Fiber Optic Cable
Moderate to high
Difficult
10 Mbps to Gbps
High, maximum effective range in 10s of Kms
High

Types of Systems

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