The signal sent out by a radio or television transmitter is made up of electromagnetic waves which travel at a speed of 300,000 km (186,411 miles) a second. The length of these waves is very important for transmission; very long waves bend with the curve of the earth. This is why it is possible to receive pictures from transmitters in Northern Africa.
But the shorter the waves, the straighter the line they travel. Thus, FM radio and television transmit on short waves. The signals transmitted travel in a straight line like light signals. The transmitter and the receiver must therefore be practically placed one facing the other.
It is impossible to pick up the signals behind the horizon. So the aerials must be placed higher so that waves can travel in straight lines from one transmitter to the next.
The higher the aerial, the better is the transmission received from behind the horizon. Another advantage is that the aerial then towers over the surrounding buildings. The risk of interference is therefore very limited. In fact, you should know hat skyscrapers and churches reflect the short waves and produce a double image.
But the shorter the waves, the straighter the line they travel. Thus, FM radio and television transmit on short waves. The signals transmitted travel in a straight line like light signals. The transmitter and the receiver must therefore be practically placed one facing the other.
It is impossible to pick up the signals behind the horizon. So the aerials must be placed higher so that waves can travel in straight lines from one transmitter to the next.
The higher the aerial, the better is the transmission received from behind the horizon. Another advantage is that the aerial then towers over the surrounding buildings. The risk of interference is therefore very limited. In fact, you should know hat skyscrapers and churches reflect the short waves and produce a double image.
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