Around the world the first form of broadcast transmission was done over the air using signal towers. But due to poor signal reception and low picture and audio quality there was move to better broadcast alternatives. These alternatives were satellite television (TV) and cable broadcasting. Satellite tv was well adopted in Nigeria but cable could not make it because it was too expensive. But due to advance in technology the old means of programme broadcasting came back offering better signal at affordable price and cost to the consumer. Now it is widely accepted in Nigeria with the name ‘Digital Terrestrial Television (DTT)’. A good example is Startimes.
DTT have some advantages over analog transmission such as channels on DTT can be viewed on personal computers. Another major advantage is the ability to watch two high quality video and audio programmes simultaneously on same station. The channels are increase.
Mode Of Transmission
In terrestrial broadcasting, programme signals are transmitted by radio waves from terrestrial (earth base) to an antenna over the air (OTA) connected to a tv. Before a programme gets to you it passes a series of process. A broadcast station sends a signal to a broadcast base using fibre optics or microwave links. This signal is then distributed through signal towers at the broadcast base. The signal gets to the antenna of a consumer which picks it and relay it to a digital tv using coaxial cables.
For people who are still using the old analog tv, conversion of the digital signal is done using a set-top box also known as decoder purchase by the consumer. Set-top box in most cases is use to decrypt and encrypted channel. The only difference between analog and digital broadcasting is that digital uses a multiplex transmitters at the broadcast base. This help in compression and improvement in signal sent or transmitted.
Transmission of these radio waves over long distance will experience delay spreads and multi fading. Another is that signal is sent from a point which the antenna must point to to receive signals. The earth going up at some point in the line of sight (earth not flat), signals will eventually hit the ground. No technology have been able to design the signals to go round the sphere. To counter this problem repeaters or multi section relays are use. These are also called signal amplifiers or locally boosters and may even look like the signal tower. They are placed at 32-80 KM apart.
Signal from terrestrial tv take a short time to get to the audience unlike satellite programmes which travel at a speed of 240 ms.
Terrestrial tv have been with us for a long time although with great improvement over the past few years. It is facing strict competition from;
- satellite tv
- cable tv
More have been discuss on these.