Goodbye analogue telly, hello digital! Part 1
Post categories: distribution
| 16:00 UK time, Tuesday, 17 April 2012
This post was written by Tom Ellinor & Martin Thorp, of our Distribution Core Technology °ù±ð²õ±ð²¹°ù³¦³óÌý²µ°ù´Ç³Ü±è.
It might be old news for most of the UK, but this week sees the final implementation of the big switchover to digital TV for the London area. ’s Crystal Palace transmitter that towers above South London, and is revered by most UK broadcast engineers / broadcast geeks, will complete its switchover in only a few days’ time.
Spectrum Analyser output for TV spectrum in the London area on April 2nd 2012. Graphic includes identifiers for the analogue TV stations and digital multiplexes (Mux)
Here at ³ÉÈËÂÛ̳ R&D’s Distribution Core Technologies group, we’ve been involved right from the very start of Digital Terrestrial TV (DTT) in the UK. We’ve helped to conceive and develop many of the technologies and standards used to build the network. Over the years, this work has included the development of prototype modulator and demodulator reference designs as well as performance testing and know-how which have been licensed commercially. The group has also contributed heavily to the standardisation of the physical layer aspects, not least the development of DVB-T2, an entirely new second generation physical layer standard, conceived and standardised in record time. So it’s not surprising that we’re more than a bit interested to watch the completion of the switchover process in our local area, and thought it would be nice to share some pictures that illustrate the process underway. These have been taken using a Spectrum Analyser that’s connected to our roof antenna here at Centre House in Shepherd’s Bush, West London.
The switchover in London is a 2 stage process. The first stage happened on 4 April 2012, with ITV1’s analogue service being replaced by the new high power ³ÉÈËÂÛ̳-A multiplex. At the same time, ³ÉÈËÂÛ̳2’s analogue service was switched off forever, being temporarily replaced by ITV1 analogue. (For anyone who’s failed to notice the intense publicity around switchover, this might explain why your VCR recording of Top Gear last week looked more like Emmerdale.) The second stage due on 18 April 2012 completes the process, with all the old analogue and digital services turned off and new high power digital multiplexes coming on air. With a hint of irony, the new high power digital transmitters at Crystal Palace actually use Inductive Output Tubes (IOTs), essentially valve technology! So the forefront of digital technology still borrows from the past.
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Spectrum Analyser output as of 5th April 2012. TV spectrum usage has changed as compared to 2nd of April and is now in the 'interim' configuration. Click for full sized image.
Be ready to rescan your set top box!! You really can’t have failed to see the publicity if you live in this city – there is even an entire Central Line tube train decked out to remind commuters of what is about to happen.
Crystal Palace has played a key role throughout the development of the UK’s DTT network. It has been used for a number of pilot trials over the years, prior to the introduction of on-air services, allowing technical performance to be measured, and niggles sorted out prior to the launch. This was the case when DTT was originally launched (remember OnDigital?), but also more recently when testing the new technologies that have enabled High Definition on Freeview.
Crystal Palace is at the tail end of this country-wide conversion so for many years we have had both the pre-switchover digital and analogue services transmitted side by side. Now that the analogue TV will finally disappear from the London transmitter forever, what will the London TV transmissions look like after the 18th April?
Pop back to this blog on 18 April 2012 to find out!
Comment number 1.
At 17th Apr 2012, Trev wrote:Unfortunatly switching to digital is not all good news. As your article mentions several times it is a system that continuousely needs retuning. We now have so many channels squeezed into each multiplex that picture quality has really suffered. For me the biggest failure of the system is that we are now lumbered with a system which cannot support an adequate HD service. Again squeezing 5 HD channels into each multiplex results in a picture quality that falls far short of being High Definition. Pictures are 1440x1080 pixels where 1920x 1080 is the standard used by other UK broadcasters.
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Comment number 2.
At 19th Apr 2012, The Grail wrote:@trevorjharris - surprise surprise - needle stuck in the groove again! Same boring old comments...you ought to get out more...well I think ³ÉÈËÂÛ̳ HD picture quality is great...mind you I don't site 6 inches away from my 42 inch screen analysing the details and not appreciating the program quality...
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