All posts by Trevor Harris
Below are all of Trevor Harris's postings, with the most recent are at the bottom of the page.
The traffic service is defined in the 2006 spec but it has not been implemented by the BBC. I don't know of any uk reciever that supports it in any case.
Infact there was a traffic service on DAB but the Government scraped it in 2011.
DAB traffic info axed The Register
That article also descibes the commercial operators attitude to DAB.
Looking into my crystal ball I would say that in the near future the BBC will have to continue to duplicate transmissions on both FM and DAB. In the longer term DRM+ may be introduced into band 2. DRM+ and FM can coexist in the same band.
I think eventually the internet will be the medium of choice.
It is interesting to see the rise of "connected tv". Internet speeds are increasing with 1gb/s available in some areas. This could make satellite and terestrial broadcasting redundant.
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Actually I have found some DAB car radios do support traffic anouncements but is a useless feature in the UK.
Ironically some DAB car radios actually do support TA by using FM RDS.
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Beware every review I have seen in car DAB adaptors have been very negative. Even the BBC did a piece on them and should that they did not work. One manufacturer was getting 90% returns and so discontinued them.
One of the problems is the aerial an FM one will not work efficiently because DAB use a different frequency band. I think windscreen aerials are dangerous because they can be distracting.
Ironically some of these units use a low power FM transmitter to connect to your radio. So you have to find a frequency which is not being used in order to avoid interference. I bought an FM transmitter with a audio input to play from phone. I live in Surrey and I could not find any frequency that did not have interference.. You need to test this with the car on the move.
I have just installed a radio (not DAB) into my wifes car. It has bluetooth and so the radio can play from the internet or from music stored in the phone.
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The problem with installing an external aerial is that can invalidate your warrenty unless it is manufacturer installed. I know some adapters can connect to the FM aerial of the car radio but then you loose FM. Some have a bypass option so you can still switch between FM and DAB but that is a bit messy.
Yep you would need a better data allowance. 4 hours a day at 128kb/s is about 7 GB/month but there are plenty of unlimited plans out there. You then get all the internet services as well.
Actually if you don't listen to FM the so called switch off won't affect you in any case.
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Giffgaff does an "all you can eat" for £12 pm. Judging by what is happening at three it looks like there is a bit of a price war at the moment.
Yep if your out of warrenty there is no problem other than it might get nicked.
@Brian Write
You raise another interesting point. Many metal framed flats will have to have DAB added to thier distribution systems if the BBC goes ahead with its plans.
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I am not sure if everyone has noticed that the BBC does not broadcast in stereo on any of its DAB stations. The BBC uses Joint stereo which encodes the stereo information in a compressed form. Like all lossey compression this produces an inferior stereo effect which has its own artifacts.
Another very contentious thing the BBC does is to apply fairly heavy digital signal processing. This not only includes dynamic range compression but also adds processing designed to reduce the MP2 artifacts. This results in the output bearing very little resemblance to the original sound.
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Not true FM does not use joint stereo. FM uses a subcarrier to transmit a left minus right signal. The left and right signals are retrieved by the addition and subraction of the left+right signal.
L= ((L+R) + (L-R))/2
R=((L+R)-(L-R))/2
This system has the advantage of mono compatability but a loss in signal to noise ratio.
Joint Stereo basically transmits the lower and upper frequencies in mono to save on bandwidth.
My argument about DAB is that it is not a suitable replacement for FM. That is why the public have been so resistant to buying DAB radios. We need a radio systems that is superior to FM to make it worth while changing. It seems that DRM+ is the best of the bunch at the moment.
The BBC has spent hundereds of millions of licence payers money on an obsolete radio system.
Some would argue that we don't actually need a dedicated radio service. The internet provides a far superior radio service.
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The other big advantage of DAB+ is that it has full Hamming error correction. DAB has a very weak form of error correction which does not do full error correction. DAB+ has a sharper cutoff point when the signal quality drops. DAB has a softer dropoff which causes the famous babling under poor signal conditions. This is one reason that DAB has black spots even well inside the coverage area.
I think it is a mystery to everone as to why the BBC did not switch to DAB+ in the early days when there were few recievers.
No matter what Ofcom says DAB+ is only suitable for national stations because it is a multiplexed system. The EBU does not recommend DAB. The EBU does recommend DRM+ where DAB+ is not suitable.
As far as I know the UK is the only country still using DAB. European countries has also experienced the lack of demand that the UK has. Most are still trialing DAB+. Sweeden has abandoned DAB+ altogether and is trialing DRM+.
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Sorry I was wrong about Sweden. The goverment will allow it's development but refused any sort of funding. There is strong opposition to a FM switch off in Sweden.
It is France that is trialing DRM+. Sorry for my country dyslexia.
I should of course have said Finland.
My point was that the most of Europe is trialing DAB+. and not DAB.
Just checked Radio 3 and you are right real stereo. So you have to tune in after 5. Great what a wonderful service only one BBC station with real stereo part time.
Actually I just tried Classic FM and guess what Joint Stereo at 128k. Even more interesting I got the burbling I mentioned earlier. You might have guessed I don't listen to DAB my ears have had centuries of fine tuning listening to a HiFi system.
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Thursday 29 August 2013 11:09PM
@briantist
I did not say that those wanting digital radio were in a minority. I said that there is a minority wanting DAB. It is a favourite scam of BBC and others to confuse the issue by using "digital radio" and DAB interchangeably.
RDS is not just about "alternative frequencies" it also supplies 9 other services. One of the most usefull is the "traffic program" which DAB does not support.
If the commercial stations want DAB why did Ofcom had to bribe the to go on DAB. I don't think any commercial station would be prepared to loose 50% of it audience with a switch over. As we know Channel 4 was unable to find any stations to go onto it's multiplex and so we still have a whole commercial multiplex empty.
Yes a interested organisations may have signed up to the plan but the public have not.
And as for DAB providing a choice of 55 stations the Internet gives a choice of thousands.