Frequencies

Very Low Frequency (VLF)

  • 3-30 KHz
  • Also known as Surface Waves
  • Propogation / Transmission through the surface of the earth
  • Radiation range is thousands of kilometers
  • Requires large transmission power due to absorption by the earth.
  • Wavelength is very high
  • Huge antenna structures required
  • Waveband is not preferred by HAMs

Low Frequency (LF)

  • 30-300 KHz
  • Progopation same as VLF
  • Range same as VLF
  • Limitations same as VLF
  • This wave band is used for Ship-shore navigational aids.

Medium Frequency

  • 300-3000 KHz
  • Also known as Tropospheric Waves
  • Propogation / Transmission through the troposphere
  • Popular Medium Wave (MW)
  • Radiation range is upto 700 km during the day but increases during the night
  • Requires large transmission power due to absorption by the earth.
  • Wavelength is high
  • Huge antenna structures required
  • Waveband is not preferredby HAMs

High Frequency (HF)

  • 3-30 MHz
  • Also known as Sky Waves
  • Most popular short wave band.
  • World Wide Communication for all services including Amateur Bands
  • Waves travel from the antenna, into the Ionosphere and reflected to a distant point.
  • The wave encircles the globe (circumference of 40,087 Kms) in 150 milliseconds over 300,000 hops.
  • The reflected distance depends upon the angle of radiation from the antenna with respect to the earth. Radiation angle determines the distance coverage, which in turn increases the reflected angle. The effect is extended distance coverage. Lowering the antenna height produces the inverse effect.

Very High Frequency (VHF)

  • 30 – 300 MHz
  • This wave penetrates the ionosphere and does not reflect back to earth, hence long distance communication is not possible.
  • It is also known as space wave.
  • It is most effective for line of sight communication and local mobile operation.
  • The range of this wave is dependant on the height of the antenna. The higher the antenna, the larger the range.
  • The normal average range is 50-75 Kms., and with an antenna can extend beyond 100 Kms.

Ultra High Frequency (UHF)

  • 300 – 3000 MHz
  • Similar to the VHF and also works for Line of Sight Communication (Space Waves)
  • Penetration into the ionosphere is even sharper than VHF and thus works very well for satellite communication and outer space communication (like with the moon or space crafts).
  • HAMs also use the lower part of this band for local communication just like VHF, but the Line of Sight is more critical here.

Super High Frequency (SHF)

  • 3 – 30 GHz
  • Similar to UHF and is exclusively used for space communication.
  • Requires precise alignment of both Rx and Tx antennas.
  • This frequency on commercial bands is used for TV and Radio Relay using Geo Stationery satellites inĀ  space and dish antennas on earth.

Extremely High Frequency (EHF)

  • 30 – 300 GHz

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