How does digital broadcasting work

A. Until recently all radio and television has used analogue broadcasting technology, which converts sound and pictures into waves. These waves are transmitted and are picked up by aerials. Instead of analogue waves, digital broadcasting converts sound and pictures into a series of binary digits (zeros and ones), which are then transmitted.

Q. Can you receive digitalised broadcasts on a standard aerial

A. The digits can be received by standard aerials, satellite dishes or by cable, but they have to be decoded once received and converted back into sound and vision. This is done either with a separate set-top box or a decoder built-in to your television or radio. The latter is known as an 'integrated' set.

Q. Is digital broadcasting better

A. Digital broadcasting is more efficient than analogue, which means it is now possible to broadcast up to six digital channels in the space that used to be taken up by just one analogue channel.

It is also very robust. Quality of sound and picture are far better than that of analogue and atmospherics and electrical blips or the close proximity of hills and tall buildings that can spoil the reception of analogue signals are not a problem for digital.

Q. How does it do that

A. With the help of a system known as COFDM, which stands for Coded Orthogonal Frequency Division Multiplex. This system uses a precise mathematical relationship to split the radio signal across 1,536 different carrier frequencies as well as across a time lag. This ensures that, even if some of the signals are affected by interference or the signal is lost for a short period, the receiver is still capable of recovering the original source and reconstructing it perfectly.

Q. Are there any other advantages

A. COFDM enables the same frequency to be used countrywide. This means that no radio re-tuning is required when travelling in a car or taking a portable television set from one area to another. In the UK there are currently 230 frequencies being used by FM stations, and national stations such as Radio One use up 22 different frequencies.

With the right equipment it also becomes possible to have interactive services on your digital television, such as on-screen shopping, banking, internet access and email. Interactive television can also change the way you watch some programmes - for example you could view sports coverage from different camera angles and create your own action replays by using your remote control. It's the future.

For more on How It Works click here

By Simon Smith