Freeview modes

Four of the Freeview multiplexes (collections of channels) broadcast in one mode known as "16 QAM (3/4)", and the other two broadcast in another mode called "64QAM (2/3)".

^{Brian Butterworth published on UK Free TV 3rd January 2006 at 00:22}

Two of the Freeview multiplexes (collections of channels) broadcast in one mode known as "64QAM mode, FEC=2/3,", and the other three broadcast in another mode called "64QAM mode, FEC=3/4".

The " FEC=2/3" mode provide a more reliable signal than a "FEC=3/4" mode signal at the same power level, but there is a trade-off that means less digital data can be carried.

This diagram shows the current channels carried on the Freeview system. The wider the box, the more bandwidth is used to carry the pictures. The more bandwidth used for a service, the better the picture quality.

Boxes split horizontally denote channels that occupy the bandwidth at different times of the day.





The third line shows the configuration of the BBC "B" multiplex switchover which is used for HD and is in another mode DVB-T2 256QAM.

64 QAM (3/4) mode

In this mode, the digital TV signal is transmitted in groups of 64 symbols. The "forward error correction" is 2/3, and this results in a bitrate of 24M.1b/s (megabits per second). This can be used to carry up to eight simultaneous television channels.

64 QAM (2/3) mode

In this mode, the digital TV signal is transmitted in groups of 16 symbols. The "forward error correction" is 3/4, and this results in a bitrate of 27.1Mb/s. This can be used to carry ten simultaneous television channels.