In preparation for the launch of national versions of BBC One HD, the BBC is changing key parameters to enable five HD services to use its HD satellite transponder, according to an announcement on a BBC blog.
The date of the technical change was changed on the "About the BBC" blog post several times, before settling on the 27th September 2012.
So, providing the BBC don't change their minds again, from the early hours of 27th September, the corporation will change the forward error correction rate on the HD transponder from 8/9 to 2/3. In addition the modulation is changing from QSPK to 8PSK. The frequency (10,847 V) and the symbol rate remain the same.
The changes will have the affect of changing the amount of available bandwidth. Currently the HD transponder transmits BBC One HD and BBC HD. Freesat and Sky users should see changes being automatically applied - although Freesat viewers may need to ensure that Freesat HD boxes are put in standby for 30 seconds in order for the change to be made. Users of generic "free-to-air" satellite receivers, including continental satellite receivers will need to make adjustments on the 27th September.
The BBC's Alix Pryde confirmed that an announcement will also be published on BBC Red Button Text informing satellite viewers that don't have an internet connection of the change.
ITV1 HD Meridian, located on the BBC's transponder is moving over to another transponder, and BBC One HD national varients for Scotland, Wales and Northern Ireland are anticipated to launch in the next few months. In addition BBC HD is becoming BBC Two HD, but the exact date hasn't yet been announced.
The national versions of BBC One HD will ultimately increase the amount of sport on HD, with sporting coverage unique to BBC One Scotland, Wales and Northern Ireland finally seeing the HD treatment.
The transponder currently in use for BBC Red Button services is expected to be ditched by the BBC, with BBC Radio services distributed evenly across remaining transponders. BBC Red Button is being reduced to just one videostream on all platforms from later this year, according to reports, with future emphasis on providing red button content via a broadband internet connection or 'apps' for smart TVs.