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• Electromagnetic waves consist of oscillating electric and magnetic fields travelling through free space at the speed of light.
• These fields have magnitude and direction (vectors) and can be horizontal, vertical, at some other angle or even rotating.
• The polarisation is the angle of the electric field and also the angle of the rods or wires of the antenna.
• Common polarisations are ...
  • Horizontal
  • Vertical
  • Circular
• Incorrectly polarised antennas don't work well at all. This can be used to advantage.
  • For example most high power UHF TV transmissions are horizontally polarised.
  • Local low power repeater transmitters serving areas of poor reception are often vertically polarised.
  • This arrangement makes interference between major and local transmitters much less likely.

Electromagnetic Waves

Vertically Polarised Dipole - Used for the automation of orange orchard irrigation.

Horizontal Polarisation - Yagi Antenna

Vertical Polarisation - Yagi Antenna

Sewage Pumping

Many sewage pumping plants are radio-linked to a central control point for environmental monitoring, pump control and fault reporting. These use UHF vertical polarisation. Interference from horizontally polarised high power TV transmitters is much less likely.

Circular Polarisation - for WiFi

Satellite Dual Antenna Low Noise Block

Circular Polarisation, Azimuth Elevation, Satellite Tracking Antenna (Old School)