POLARISATION

To answer this question , we need to understand a couple of things . Television signals – a type of radio wave – in Australia are broadcast either horizontally-polarised or vertically-polarised . Because radio waves comprise an electric and magnetic field , they are ‘ polarised ’, which refers to the ‘ plane ’ in which the wave of the electric field moves . A horizontally-polarised signal will move sideways , while a vertically-polarised signal will move up and down . Therefore , to receive a horizontally-polarised signal , your TV requires an antenna designed to receive horizontally-polarised signals – it ’ s the same story for verticallypolarised signals .

Not all countries use this dual polarity system . Television signals in the United States , for example , have been traditionally broadcast on a horizontal plane only , which is why some American-made television antennas perform poorly in Australia , as they can ’ t receive a vertically-polarised signal .

Australia ’ s broadcasting towers are split roughly 50:50 between horizontally and verticallypolarised signals . If you ’ re in an area with a horizontally-polarised signal but your aerial is designed to only pick-up vertically-polarised signals , and vice versa , you ’ re out of luck .

If having a mix of horizontal and vertical signals seems unnecessary , there is method to the madness . Essentially , the reason for horizontally and vertically-polarised transmissions is to prevent signal interference between broadcasting towers , therefore increasing the number of stations that are available and thus creating better TV coverage .

Diagram showing the difference between horizontally and vertically-polarised TV signals .

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