London DSO

If you'll excuse the terrible website: there's a DSO-related exhibition on at a gallery on Marylebone Road, with 1001 TVs, flickering away. Presumably some are tuned to ITV1, so will go to static next week, and the rest a fortnight later.

http://davidhallart.com/bio.html

That is what I had gathered from comments on a couple of YouTube videos I'd seen - hence why I said "I understand" - I wasn't claiming it to be the truth. Clearly what I had learnt was wrong, though!

So...those of us who might be staying up to see them go (ahem...just enquiring for "a friend"....!) shouldn't wait up for Channel 5 then?

Although of course as they don't need to clear that frequency, there's no need to send someone to Croydon until the big job at CP is done.

I don't really see why they would go to the effort of backing up a service that's about to cease, and at Stage one they do some tests in the new high-powered MUXs don't they?


For those few still relying on analogue. It's probably a good extra way of pointing out to them that things are changing.

Sounds like it's best if you... er, your friend... might be better off watching everything switch off and then go to bed and set your alarm for 8ish.

Although of course things come on-air though out the night so you might want to get the matchsticks out

I know that Crystal Palace doesn't have a generator back up, instead it uses they use supplies from 2 separate parts of the grid. I'm not sure if this is just because it's in an urban setting or whether it's the case in other sites too.

This sounds interesting: http://www.arqiva.com/corporate/press/archive/2012/2012-3-26%20-%20Crystal%20Palace%20tower%20lights%20up%20the%20London%20skies.pdf

No, but at Stage 1, BBC 1 and C4 analogue with probably have to go off the air overnight, while the new PSB 1 Tx is plumbed in, (replacing the old ITV analogue transmitter). The BBC 2 analogue tx will need to have its input changed over to ITV.

It would be a lot easier, to switch the whole lot off at CP at midnight, and instantly switch BBC 1, ITV (ex BBC2) and C4 on at Croydon, for the few hours the replumbing at CP will take ?

We'll find out in 8 days from now !



Yes, true !



Yes, all main sites, with the exception of Bilsdsale (very remote) and Rowridge (on an island )

Generator back up is however used for DTT at all main sites, and that will continue post DSO, (with upgraded units to cope with the higher power),

If 1 and 4 have to go off then I'd have thought that 2 will as well. Any idea how much 'plumbing' actually needs doing? They've been testing the new MUXs over the last few months so wouldn't they already be connected to the aerials? Or is the overnight work more about finalising the new setup and removing the old TXs from circuit

I assume that putting ITV into the old BBC2 TX is just a case of running a cable through from the ITV/C4 part of the building to the BBC transmitter room.



Interesting. I assume it's more viable to do that for DTT because there's less power needed?

They need to unplug the brand new transmitters to plug in the lights though

AIUI at present the analogues are being radiated from the uppermost aerial (S1). Low power DTT is from the lower one, S2, that will act as standby post DSO. Post DSO channels will use the S1, so between April 4th and 18th, the S1 will carry PSB 1, BBC 1, ITV, and C4. I've visited another site on DSO eve a while back, there's an awful lot of temporary feeders (and by feeder, that's 6inch diameter copper piping) connecting the old analogue transmitters, to the new 6 Tx DTT combining units. Everything is duplicated for the upper and lower half of the aerials. The high power tests that are conducted a few months prior to DSO, usually do one half of the aerial at a time, and the second half the following night, to minimise disruption.

London does have the luxury of having the four analogues backed up at Croydon, and Croydon does seem to have been used for periods recently (a few hours at at time) to allow complete of partial shut downs at CP for DSO work;



That's what I thought, but at most other sites where similar swaps have occurred, the swap is done post TIE/PIE bays at the RF drive stage ! I'm told it's simpler, and saves messing about with very different legacy methods the BBC and IBA had for input signal processing, and telemetry.



Yes ! Though there's an enormous genny at Rowridge, where total Tx power (up the feeders) is very high, owing to horiz and vertical radiation components post DSO