British, Terrestrial, Digital TV service.

OnDigital is the alternative to Sky Digital for British viewers who wish to recieve digital TV through their existing aerial, rather than through a satellite dish.

6 UHF frequency bands each carry a multiplex of several digital streams. Most of these are MPEG streams, although some of them contain teletext and EPG data.

Unlike American digital TV schemes, there is no element of HDTV involved: these broadcasts are at normal TV resolution. Many programs are broadcast in 16:9 widescreen format however.

The UK has only five analogue terrestrial channels, so the 30+ provided by OnDigital are welcome (although only a few of these are non-subscription) -- however SkyDigital provides dozens more channels via a dish.

I've just bought my set top box, and although normally the picture is excellent, electrical interference (e.g. from thermostats switching) often causes glitches in the picture. For analogue reception this causes tolerable flickering in the picture -- but for digital broadcasts all sorts of ugly MPEG artefacts show up: mosaicing, break-ups in the sound, freezing etc.

For a flat fee of £40, OnDigital will do whatever aerial upgrades are necessary to correct such problems. When I've had that done, I'll let you know how much it's improved.

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