Help with TV/radio stations?
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Tuesday, 21 February 2012
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Steve P11:20 AM
FIGHT for MW and LW.
They will always get to places the others cannot reach.
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Mark7:39 PM
@ Dave Lindsay
That's true up to a point, but there will be public funding for local DAB multiplexes (from the DCMS & the BBC) and the North Devon mux will reach well over 90% of the area's population before Radio Devon on FM is switched off.
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Mark: Thanks. So the commercial operators do get some support.
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Alvin Pritchard9:04 PM
If the powers that be addressed this low bit rate issue once and for all maybe more manufactures of DAB and DAB+ Hi-Fi Tuner separates would release more models as these are far too thin on the ground at the moment,currently portables dominate this sector.
A good well designed solid DAB Tuner separate will always be a good investment in any domestic Hi-Fi setup.
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Wednesday, 22 February 2012
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michael9:57 AM
Some areas may not get an acceptable indoor or in-car DAB signal when the existing AM and FM transmitters are switched off. The BBC will not be able to piggyback where commercial operators choose not to invest. Heart (formerly Lantern) set up a local FM relay years ago to cover our coastal black-spot. The BBC did not follow suit; there was no need as AM gives good coverage almost everywhere. If Heart replaces the FM relay with a DAB one, would the BBC be under a legal obligation to use the commercial multiplex for a Radio Devon DAB relay? If Heart maintained the status quo, there would be no chance of DAB reception of BBC Radio Devon in many valleys and coastal locations. Similar scenarios could arise in other parts of the country. This might result in compromise, with some AM and FM transmitters being saved from the chop. The future continues to offer more ifs and buts than bits and bytes...
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Mike Dimmick2:51 PM
Alvin Pritchard: The only ways to fix the problem are to close some services, to allocate some additional frequencies, or to convert to a more efficient standard.
Despite the actually fairly low number of DAB receivers out there, the government have completely ruled out an upgrade to DAB+ until at least after switchover, possibly ever. This is, in my view, idiotic - voluntary takeup is stalling and will continue to stall with DAB as the deployed technology. Remember that DAB started up *before* digital terrestrial TV, it did so in an empty spectrum band, not one already congested with high-power analogue services, and it still hasn't achieved 50% of listening.
While you can do a piecemeal upgrade, as DAB+ is simply a different format of data carried on an underlying DAB data stream, you have to decide which service or services will no longer be receivable on DAB devices - unless you also have some more frequencies.
VHF Band III signals travel a long way and bend well over terrain - compared to UHF TV signals, but less far/bendy than FM (VHF Band II) or AM (Medium Wave, Long Wave) - so must be co-ordinated internationally and across the country. There are 24 frequencies that can be used (excluding those that overlap), but we only have rights to use some of them.
We have actually negotiated block 11A for the second national commercial ensemble. This was licenced to Channel 4 and partners as 4radio, but didn't launch. We could possibly launch national BBC DAB+ services on 11A, if there's some way to get DAB+ receivers to only tune in the DAB+ transmissions - and if someone else will pay for it, or the government will allow the licence fee to rise with inflation again, as the BBC are a bit strapped right now.
Or, of course, we could continue with DAB and fill National 2 with BBC and commercial services transferred from the other ensembles, allowing bitrates to improve for the other services.
Alternatively, we give up DAB completely as a bad loss - as DAB+ isn't significantly more efficient, it's actually less efficient in bits/Hertz - and encourage take-up of some other technology. The promising candidates are DRM+, which deploys in existing radio bands alongside existing transmissions, much as digital TV has, or DVB-T2 taking over DAB allocations. Yes, DVB-T2 was originally designed for TV but it's really just a way of transmitting an ensemble of data streams, and it's a lot more efficient than DAB or DAB+. If you're going to break everyone's receivers, you might as well do it properly!
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Mike Dimmick4:35 PM
michael: The whole ensemble must be carried on all transmitters that carry it, because all transmitters using the same frequency must carry the exact same bits, very closely synchronized. Extending coverage to additional transmitters will probably require negotiation between the services carried on the ensemble and the multiplex operator, to distribute the costs accordingly. That is, if the existing frequency can continue to be used in the new location without either interfering too much with another user of the block, or too much self-interference.
DAB does allow for a service to be carried in different ensembles in different parts of the country, which I believe are linked (similar to RDS) allowing mobile receivers to retune automatically. For example (picking the top one from the list) Absolute Christian Rock transmits from numerous local ensembles, with different frequencies but always with service ID C7C9. However, because of the relative shortage of frequencies, it's unlikely that a very small service area would be created just to allow some services to opt out of an extension of the main coverage area.
In fact North Devon carries the same ensemble as Exeter & Torbay, only on block 10C rather than 11C. They have been licensed to the same operator. So radios will retune automatically on moving from south to north Devon and vice versa.
Ofcom's DAB coverage consultation is based entirely on equalling, as far as possible, both the BBC Local Radio and Independent Local Radio coverage areas. Ilfracombe is included as the second transmitter in the list, after Huntshaw Cross, although I have to admit I don't see where they get the population percentage increase from!
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Sunday, 26 February 2012
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Alvin Pritchard4:42 PM
Mike Dimmick: You write some very interesting observations on this topic, but asking over a million owners to scrap their standard DAB receivers so the nation can start afresh with a new digital format is going to be asking for the impossible.
It looks as if we have shot ourself's in the foot by diving straight in and opting for DAB as a national standard C/w with all its foreseen limitations as we are now caught between the devil and the deep blue sea, the only way forward now in my opinion would be for manufactures to ease in DAB+ or DRM+ on all new models as these formats are backwards compatible and this option would keep sales going until the level of ownership eventually gets to a level to warrant a switch over.
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Monday, 27 February 2012
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Mark7:01 PM
DRM+ is not backward compatible with the DAB network, the BBC would have to tear down its DAB transmitters and start again.
However the good news is that DAB+ can be broadcast on the BBC's current DAB transmitter network without any further expense necessary, and of course it's much more efficient than original DAB.
DAB+ is quickly becoming a de facto digital radio standard in Europe, with Germany, Italy & France all intending to use it.
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Mark: DAB+ introduces only a new data compression layer to the system, it doesn't change the nature of the COFDM transmissions. So DAB+ receivers are backwards compatible, so using it for transmissions renders DAB equipment useless.
DRM/DRM+ is a totally different type of technology which is designed to "fit into" existing radio broadcast bands, whereas DAB/DAB+ uses a section of the old VHF TV network allocation (a quarter-channel per mux).
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