I started a thread on this topic around this time last year, so i thought i would do the same this year!
Digiguide now has listings for BBC ONE and BBC TWO in early January 2006. However, the listings dont show any details of an analogue shutdown yet.
Any ideas where a shutdown could slot into the listings? Does anyone else know any details yet?
The early morning of Friday 6th January 2006 looks most likely (the last engineering test was Friday 7th January 2005). BBC ONE ends programmes at 3.30am. So, the BBC ONE test COULD be 3.30am - 4.30am. BBC TWO finishes programmes at 2.00am and then joins BBC News 24 until 3.30am. So, the BBC TWO test COULD be 2.00am - 3.00am. This follows the exact time pattern as the last test.
BBC2 closes down at 2.30am on Friday 7th January after which The Learning Zone returns so it probably won't be then. Maybe the engineering shutdown will be on Saturday 8th January on BBC2.
BBC2 closes down at 2.30am on Friday 7th January after which The Learning Zone returns so it probably won't be then. Maybe the engineering shutdown will be on Saturday 8th January on BBC2.
Friday 7th January 2006 doesnt exist. Saturday 8th January 2006 doesnt exist either.
The Learning Zone returns to BBC TWO at 2.30am on Saturday 7th January 2006 (according to Digiguide). The BBC Engineering tests are most likely to be in the early hours of Friday 6th January 2006 (as i have already said).
The usual test done during these shutdowns is that of the Rebroadcasting System (RBS). Most (all?) transmitters have a system built in whereby if they lose their incoming main feed of BBC1 and/or BBC2 for a set amount of time, they pick up the signal from their nearest transmitter and 'rebroadcast' it. During this test, the engineers in London cut the feed of BBC1 and BBC2 to the network and instead only send it to Crystal Palace. All transmitters other than CP lose their output, then steadily the ones nerest to CP go into rebroadcast mode (RBR), then the next ones and so on all the way up country. Engineers across the country then watch the output of their local transmitters and report back when they manage to get a signal again. Testcard fans often get a good long look at various test patterns sent from London so that various quality checks can be made.
It's very unlikely that the signal in Northern Scotland would ever be a rebroadcast of CP (effectively) but it's often amazing how reasonable the picture quality can be. It's far more likely that (for instance) Sutton Coldfield might lose it's feed and would switch to rebroadcasting the output of the Oxford transmitter.
RBS (Re-Broadcast Standby) is almost instantaneous. I think the setting is about 1/2 second no more, perhaps less. A "tool" sometimes used to fix faulty equipment in a region. I've pulled the outgoing U-Link before now and not seen the picture glitch in any way. Only the 'scope shows a marginally impaired trace!
Note, each region gets a direct Energis line feed of BBC1 & BBC2 analogue and passes it on to their main transmitter. If this feed fails or doesn't pass certain tests at the transmitter then the TIE (Transmitter Input Equipment) will automatically switch to the RBS feed, very quickly.
Regional engineers will be looking on 'scopes to see that the off air feeds are of reasonable quality, and that the RBS switch has happened..
Threads like this always make you want to ask questions, though I generally never fully understand the reply - but why is it only the BBC that do these?
I wonder if the Beeb have to pay extra "bank charges" to have someone come in in the middle of the night and whip out an odd u-link, here and there, to trigger the tests?
Don't forget the smaller tests - recently I spotted a small white marker on BBC1 analogue from Belmont that wasn't present on digital, usually a small flicker when it's removed. I've seen similar tests from The Wrekin using a different marker the past few years. Usually seen during the sign zone.
