BBC Licence Fee Channels on 27.5w

Yep, from my (very brief) time there i think it was 2 satellites (called Orion although I don't think these exist now) each with 2 of their 4 regions on. They could switch any transmitter remotely to any of the 4 allowing for very specific adverts or opt outs If they ever felt the need.

Croydon had a line feed added and they added a 5th region, I think when Astra was added (although as their playout centre and server farm was built around 4 regions, I don't know how they crow-barred in the extra one so soon!). Presumably the old 'region 1' became London via line feed and the other 4 (2-5) became the dynamic satellite fed ones

Off topic slightly but something I've never understood about ENG uplinks...

Satellite transponders for DTH carry several different services all multiplexed together on earth and uplinked from a single site.

But with sat trucks they're all in different locations so their signals can't be MUXed on the ground, and they'd double illuminate if more than one uplinked to the same transponder. So how does that work, do they share transponders somehow or do they have lots of little sections of bandwidth for each ENG truck?

Yes, each uplink uses a 'small' symbol rate, just enough for that particular stream, and a spot carrier within the allocated transponder range. Nevertheless I think the carrier must be locked to a common reference, that can only be GPS derived ?

That is because consumer broadcasts use MCPC - Multiple Channels Per Carrier - and multiple multiple video, audio and data streams onto one high symbol rate carrier that takes up a large amount of bandwith. (Typical symbol rates of 22k, 27.5k, 29k)

SNG and OB uplinks can run using SCPC - Single Channel Per Carrier - and carry just a single video and audio stream on a much narrower bandwith portion of a transponder with a low symbol rate carrier. (Typical symbol rates around 3k-6k)

NB Symbols are not bits. QPSK encodes two bits per symbol, 8PSK encodes 3 bits per symbol.

SCPC isn't as efficient as MCPC as you have to allow some guard bands between different carriers on the transponder to avoid interference, and you also can't stat mux. However it is the only real way of using a single transponder with multiple uplinks from different locations.

Thanks for the replys, interesting reading, Five feeds are also on 16e as well also in PowerVu along with the likes of Setanta Africa (also Powervu)

I can receive this transponder quite easily, however I can't get any video or audio out of it (my receiver has picked up the names and all the channels have VPIDS/APIDs assigned (seems to stay locked at about 82% quality, 88cm dish):



I would like to see what something like TSreader has to say about it, however it (TSreader) absolutely refuses to work with my DVB-S2 card.

interesting my box cannot pick it up at all.

AIUI, these feeds are redundants for use across the UK, including at BBC centres across the country (I.e. the Mailbox in Birmingham where I've witnessed these feeds coming in, and Salford Quays in Manchester and Broadcasting House in Belfast). Again, as I understand it, the downlink station for Virgin Media at Brierley Hill in the Black Country also uses these feeds as a redundant, including the Channel 5 ones at their cable head-end that is based there, and also for their premises at the nearby Waterfront.

I'm not sure about whether there are downlinking capabilities at the tx's for these to be used as sustaining DTT relays, I'm pretty sure Sutton Coldfield for example doesn't have a set up pointing to 27.5, but I'll ask a bloke who definitively knows and report back!

well gave it another go, still can't pick these up except for Channel 5, except that's in PowerVu.