DAB, Digital Radio, Digital Audio Broadcasting, Review, Reviews Opinion, Information

	DAB Digital Radio - THE FUTURE OF RADIO?
	ADVANTAGES OF DAB TO THE LISTENER: > Very easy station location using a simple menu and station name display with no 'tuning' - a massive boon! > New stations not available on FM or AM are available on DAB: e.g. specialist music, news, sports, spoken word,comedy > A fairly wide choice of radio stations, particularly in metropolitan areas > Good reception is possible in areas of good signal strength > No AM type crackling or buzzing and no FM type hiss and multipath distortion > Quite good sound quality is possible - BUT only when high bit-rates are used by the broadcasters - (generally audio quality is poorer than FM) > New ranges of easy to use radios and tuners are available for portable, home hi-fi and car use.. I particularly like the PURE range of 'EVOKE' portables, which are solidly built, easy to use, have great reception sensitivity for weak signals and sound better than all ather competing radios that I have heard.
	THE DISADVANTAGES OF DAB THAT MUST BE CONSIDERED: > Station choice is dictated, and thus limited, by the particular multiplex* operator who may tend to favour only stations owned by their particular broadcasting conglomerate - thereby excluding competing and maybe more interesting radio stations. see note below > Reception is often unsatisfactory in areas of marginal signal strength on portable DAB sets - marred by severer background "warbling sounds" - like boiling mud - that are more annoying than a little bit of FM "hiss". > An external DAB aerial is essential in these marginal areas otherwise sound can be marred by burbling noises. > The MPEG type of digital compression used by DAB is now already archaic and out of date and demands higher bit rates to produce reasonable audio quality compared to modern digital compression systems - commercial broadcasters seem to avoid high bit rates wherever possible and thereby force listeners to endure poor sound quality that is much worse than FM radio. > The Ultimate sound quality achievable can approach that of the very best FM reception when high bit-rates are used - but can never be anywhere near the 'CD' quality that is sometimes erroneously claimed by the advertising (This claim has since been quietly dropped and the phrase 'crystal clear sound' is more often used, though this is of course completely meaningless! The audio on my telephone is crystalclear, in that I can understand every word being said - but you could NEVER describe a phone call as Hi-Fi !) > LOW BIT RATES : When the dab system was developed, high bit rates of 256 or 192 kbps were intended, and as such would give a sound quality that coild almost approach that of FM radio standards. However the broadcasters have opted for vastly inferior bit rates in many cases of 128 kbps, which provides a very annoying and very poor sound quality when compared to FM or CD sound. Some commercial broadcasters are lobbying Ofcom for even lower bit rates - down to 96kbps - which is utterly disgraceful and will give woeful audio. > Choice is restricted in some counties/regions where no local multiplexes can technically be made available. > DAB is not a worldwide standard. The Americas, for example, have not adopted DAB so DAB radios will not work in those countries. Other countries that do run DAB may use incompatible frequencies, eg Canada - and even in Europe it has not been universally adopted and some countries such as Germany and parts of Scandanavia may even drop DAB altogether due to its technical deficiencies. YES - FM really does usually sound MUCH BETTER than DAB! OTHER CONSIDERATIONS: > The government has not released enough radio spectrum to allow full local coverage - though OFCOM is releasing additional frequencies in due course to improve national coverage and allow every area of the UK to have a local multiplex. > As established radio companies operate and charge for carriage on the individual multiplexes*, these operators therefore have the ultimate political control and influence over which radio stations are (or are not) carried. > Smaller local independent stations (currently operating on AM or FM) are priced off the local multiplex particularly if the multiplex is operated by a competing radio group or conglomerate. > Will we be sacrificing high quality analogue FM radio on the altar of MUCH lower quality digital radio and greater station numbers?
	GENERAL CONCLUSION A good radio delivery system that, in operation, is very user-friendly but is utterly compromised by the [commercial] broadcasters desire to transmit programmes at less than adequate bit rates (128 kbps - or even lower if they get their way with Ofcom) thereby making the audio quality very poor in most cases - and completely unlistenable for many listeners who have a good sense of hearing and a good Hi Fi system that with ruthlessly expose the awful quality of many staions carried on DAB. Sound quality could be quite good with high bit rates (192 kbps) but due to the lower 'bit-rates' adopted by most stations/groups/conglomerates DAB can be regarded mostly as an opportunity missed and a great disappointment. It is an improvement over AM stations, but does not any where near match the sound quality available from a high quality FM tuner and certainly not up to the standards available from CD via a good Hi-Fi system. The sound is usually acceptable for portable listening but not for serious music, or indeed speech, radio requirements. Wide choice of stations not available on AM or FM - particularly BBC radio. An improvement in sound quality over AM stations such as BBC Five Live, Virgin, Talk Sport, and oldies stations. Choice is, however, not as wide as is available on internet or satellite delivered radio, but should be more than enough for the great majority of listeners. DAB is ideal for car radios as it is easy to find the required station and subsequently needs no further re-tuning, but reception quality can be very poor and unlistenable when the signal is not at its strongest. DAB does not cover as much of the UK land area as analogue AM and FM radio and the signals are often weaker. There is no background interference on a good DAB signal, the crackles of AM and the possible hiss of FM are absent. However the DAB signal needs to be quite strong otherwise the audio can be inturrupted by irritating burbling and warbling noises which are extremely annoying, or the sound may be muted altogether if the signal strength drops due to passing vehicles or the movement of people etc. Therefore a good externally mounted Band III aerial is recommended where reception is unreliable, but these DAB aerials are quite inexpensive. A question mark perhaps hangs over the operators of certain multiplexes concerning how and which stations are carried locally. A Question That Must Be Asked: Are we replacing a high quality sound delivery system - in the form of analogue FM broadcasting - with an inferior sounding digital delivery method simply in the drive for greater number of radio stations?? Overall - Interesting if you are looking for some extra stations and especially if you are listening on a good quality portable such as those produced by PURE and with a good aerial. BUT you must accept the much lesser audio quality of DAB when compared to FM radio.
	*NOTE: A MULTIPLEX is a DAB radio channel that is used to transmit several radio stations or services. The Multiplexes are organised thus: One National BBC Multiplex carrying the BBC national radio stations incl. BBC Six Music, BBC7 & Five Live Sports Extra. One National Commercial Multiplex (operated by Digital One) carrying various national independent stations such as Virgin Radio, Classic FM, Talk Sport, OneWord etc. One (or sometimes more) Local Commercial multiplexes carring local radio stations and which are obliged by OFCOM to carry the local BBC station(s). Several Regional Commercial multiplexes carrying regional independent radio stations.

DAB COVERAGE MAPS
To Give You An Indication As To Whether You Are Within The DAB Reception Area

Interesting And Useful Link About DAB and VHF/FM Aerials:
http://www.aerialsandtv.com/fmanddabradio.html

DAB - A GENERAL OVERVIEW

Now that the long wave, medium wave and vhf/fm bands are effectively full up and can accommodate no further stations, DAB could be the ideal way to expand future domestic radio broadcasting.

DAB is a system developed by the BBC and European broadcasters under the EUREKA 147 project and has been adopted by the EBU (European Broadcasting Union) as the future standard for digital audio broadcasting in Europe. DAB has been adopted by numerous other countries around the world too, with the notable exeption of the USA where the FCC is experimenting with a different digital broadcasting standard known as IBOC (In Band On Channel) which piggybacks a digital service alongside a current station on FM. IBOC has not proved to be a complete success as yet, however.

DAB, meanwhile, is transmitted in vhf band III (174 to 230 MHz), the band that the old 405 line black and white televison used to occupy in the UK from 1955 to 1982. Many areas can receive three multiplexes; the BBC National DAB Multiplex: the national commercial multiplex Digital One : and a Local Multiplex operated by a commercial operator. Some heavily populated areas can receive a additional regional multiplex. In my own area which has good radio reception, I can receive BBC, Digital One, a regional multiplex (MXR), a local multiplex (NOW), PLUS two other 'out of area' multiplexes (TWG-EMAP and CE Digital).

Each Multiplex can carry several radio stations, perhaps six or more depending on the data rates of each station. The lower the data rate of each service the more programme choice can be provided - but at lower audio quality. Typically 160 or 192 kbs is required for good audio quality and these rates are sometimes used by national music stations. 128 kbs is accepted as the minimum quality required for music reproduction, although the audio quality is really rather annoying when compared to FM or CD, and this is the rate used by most local music stations and is set by the commercial operator so that maximum revenue can be squeezed out of the multiplex from the greatest number of stations carried.

The fabulous sounding little Pure Evoke 1 portable DAB receiver - now in improved "XT" form!

DAB is eminently portable, quicker and far easier to use than any other type of radio delivery system and offers very good sound quality, much better than AM and free of the hiss and crackles, pops and multipath distortion that could effect FM reception.   Technically the sound quality is not as good as that which can be achieved with a standard analogue wideband FM band II vhf signal and when comparing a 128kbs stereo DAB station with a good analogue broadcast on FM via a high quality hi-fi tuner the DAB sound quality is VERY noticeable worse. However given the good bit rates (160kbs - 192kbs) offered by Classic FM, Virgin Radio and Radio Three the sound quality is a little better if being played through a hi-fi system, though subjectively still not equal to a good FM signal. I prefer FM every time over DAB.

HIGHEST QUALITY: If you are looking for the best radio quality then you need to consider radio via digital satellite - the SKY system - or via digital terrestrial television - i.e. Freeview.

DAB currently has one and has one major advantage over FM radio, that of significantly lower audio compression, such as the awful Optimod and Omnia systems so heavily used by most stations on FM.   I use a Pure Evoke 2 for portable use, and this offers quite amazing audio from its built in ported hi-fi speakers on FM and the high bit-rate DAB stations. The Pure range of radios are really quite impressive despite the poorer sound quality offered by most DAB stations.

The lack of audio compression is, of course, purely at the broadcasters whim. As DAB is more widely adopted by the listening public there is a chance that audio compresion may gradually be introduced on some stations, which would be a shame for an audio broadcasting medium that can offer reasonable audio quality without the hiss and crackles of FM and AM.

DAB seems to me to be an ideal portable digital radio medium, but I think the system should be used to expand choice rather than to simply replace the existing AM and FM bands, and certainly 'squashing' (digitally compressing) too many stations into each DAB multiplex will have a very detrimental effect on sound quality due to lower bit-rates that would then have to be employed.

The down-side of DAB is that the listener will really only hear those stations that the authorities (the government and Ofcom) and the multiplex operators themselves deem that they want you, the listener, to hear. Since each block of frequencies (multiplex) is re-used over and over again the possibilities of DX-ing (distant reception) other services and stations is very limited since the chances are that a distant multiplex will be blocked by a more local one using the same frequecy block.   It's not the same as AM or FM DX-ing whereby a listener can 'weedle out' a distant station from in-between two more local transmitters by careful tuning and adjustments.   So we are in danger of becoming far too regulated and restricted in this respect. Where I am located I can listen to Alan Beswick on BBC GMR many many miles outside the service area of BBC GMR on FM by careful tuning and a strategically placed dipole aerial, I have no chance on DAB however, so that avenue of enjoyment would be cut off if FM did not exist.

The biggest problem, it seems to me, is the one of which radio stations and services your local multiplex operator allows you to hear. If they don't want station 'Y' carried on their multiplex for economic or competitive reasons then they don't have to carry it. The smaller radio stations may be priced off the local DAB multiplex simply because the multiplex operator can charge what it wants to allow a station on to its programme stream. If a particular radio station cannot justify the costs being charged by the local multiplex operator then it simply will not be carried and could be left 'ghettoised'.

This is very worrying and could lead to anti-competitive practices, since all the local multiplexes are owned by the very big radio groups/conglomorates, and with ownership rules and regulations being relaxed by Ofcom, these multiplex operators will inevitably merge and consolodate and be in an even stronger position to squeeze out the smaller stations from their DAB multiplex 'market'.

Since the BBC has only been allocated one single national multiplex and no local multiplex the authorities (Ofcom) have required the local commercial multiplex operators (i.e. Capital, GWR, EMAP etc) to carry the BBC local station in the area on their multiplex.

Here is the other rub. The government only allowed a very small portion of the band III v.h.f. spectrum to be allocated to DAB broadcasting, this limited number of frequency blocks means that many areas of the UK will have no band III local DAB multiplex. In consequence areas with no local commercial DAB multiplex available cannot be provided with coverage of BBC local radio on DAB in that area. The areas that will have no local DAB reception on band III include Oxfordshire, Cambridgeshire, Suffolk, Lincolnshire, Kent Coast, Somerset, North Devon, Derbyshire, Nottinghamshire, and Northern Ireland (which has to make do with one combined national / regional commercial DAB multiplex).

In 2005 OFCOM announced that additional frequencies in Band III v.h.f. may be made available to expand national commercial and BBC DAB coverage and to guarantee that every area would have its own LOCAL DAB multiplex. The expansion of local multiplexes to fill in uncovered 'white' areas commences in 2006 and may take several years to complete.

DAB could offer excellent expansion opportunities and reception quality and a good choice of new stations, but perhaps it should not be at the expense of current AM and FM bands just yet. DAB is still in its infancy we cannot tell how the authorities will treat the development of this new medium or, indeed, the future development of domestic radio in general.

There will be additional possibilities for expansion of DAB into local areas without current reception with the introduction of services in a new higher frequency bands. A new DAB band in the 1400 MHz region may be released in or after 2007 to allow more expansion of very localised DAB services. The trouble is that nearly all DAB radios sold to date do not include these new frequencies and will be unable to exploit the new services. This seems quite daft planning on the part of the UK government (hardly surprising then, I suppose) that all current DAB radios can receive all the frequency blocks in vhf band III (174 to 230 MHz) but that the government only chose to use a limited number of blocks in a very small portion of this band for DAB - hopefully this situation will soon change after 2005.

This is no doubt due the the fact that rather than institute good DAB planning, the government have auctioned off these more suitable frequencies to make a quick buck. But whenever did the government do anything sensible, practical, economical or popular with the common-sense thinking public? The usual government motto seems to be 'If a job is worth doing it's worth fudging and botching and making inefficient and almost unworkable'.

So at the moment we are left with a typically British compromised system.

The radio manufacturers have come up with some pleasing, interesting and quite good sounding portable designs. The broadcasters, particularly the BBC, have put some good stations on the multiplexes. Sound quality, however, is the biggest disappontment and cannot even match the heights of top-quality FM radio, let alone CD, due to DAB's currently restricted bit-rates. DAB is generally free from crackles, however. We can hear BBC Five Live and Talk Sport in higher quality than that available on AM and have the benefit of additional services such as BBC7 and BBC 6 Music and Oneword to name but a few.

We are, of course, waiting for the additional space allocated on band III to bring DAB to unserved localities. It is slightly worrisome that the commercial local multiplex operators (owned by big conglomerates) are in a position to dictate what we can and cannot hear and price some stations off DAB altogether. Let's hope that DAB is used to expand choice rather than simply a means for the government to close down the VHF/FM and Medium Wave and Long Wave bands so that they can sell those frequencies off to make yet more fast bucks to pay for the usual government follies.

I am extremely pleased with the PURE EVOKE-2 DAB radio, the additional stations are very welcome and the set is extremely easy to operate. Such a shame that the broadcasters have spoilt the potential sound quality!

The Pure Evoke 2 is a high quality stereo DAB portable
receiver with additional FM coverage. The Pure Evoke 2
is ideal for the kitchen window shelf,
bedroom, lounge or study.
The sound quality is absolutely first class.

I am a huge fan of the PURE range of receivers, they are superbly designed, well built and solid very easy to use and sound fantastic.
I would go as far as to say that they must be among the best, if not THE BEST DAB receivers available.
See the excellent retailer JOHN LEWIS for the range of PURE EVOKE DAB radios.

DAB COVERAGE MAPS (click here)

EXTERNAL LINKS:

www.aerialsandtv.com - Aerial installations, theory and practice

http://www.aerialsandtv.com/fmanddabradio.html - FM and DAB Radio Aerials

www.atvcircuitsandservicemanuals.co.uk - TV service information

http://www.wrightsaerials.tv/ - Bill Wright's aerial installers website

For a comprehensive frequency and station listing of what is available from DAB digital radio and what this system can offer you,
please visit Dr. Paul Groves' page FREQUENCY FINDER UK

Also have a look at these useful pages:

BBC Reception advice

BBC Digital Radio

BBC Local Radio

Digital One

MXR - Regional DAB multiplex privider

RADIO-NOW.co.uk

PURE DIGITAL

dab-digital-radio.com

DAB Ensembles Worldwide

Related link:

Some notes about Digital Terrestrial Television (DTT) - FREEVIEW and TOP-UP TV

MORE RADIO LINKS:

Radio Links Page

DAB Coverage Maps

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