DAB+ radio broadcasting has a long way to go
This month, we have a couple of letters discussing DAB+ and the main one is from Joan Warner, CEO of Commercial Radio Australia, promoting the cause of DAB+ against those who would argue that it has been a disappointment. From my point of view, DAB+ is a disappointment because its sound quality is usually nowhere near as good as it can be. This topic has been raised in our Mailbag pages several times since the introduction of DAB+ and nothing has changed to cause a reassessment of that view.
The basic problem is that most broadcasters have elected to use too low a data bit rate and therefore audio quality is severely compromised.
While this may be of no real consequence for stations that are mainly talk-back and sports-oriented, it is pretty poor for stations that mainly broadcast music, whether it is classical, rock, country & western or whatever. Perhaps the worst example is the DAB+ station ABC Classic which broadcasts the same program as ABC Classic FM. Sadly, the sound quality from the FM stereo broadcasts is clearly superior to that from DAB+. This is a pretty poor effort from the national broadcaster.
Furthermore, as bad as it is, sound quality is not the main issue. DAB+ can be an advance for listeners in areas of reasonable signal strength where existing reception from AM or FM broadcasts is noisy and subject to interference. AM radio seems to be particularly subject to interference from digital services such as ADSL and pay TV where there are above-ground cables present and DAB+ can be a revelation by comparison. The fact that there are many extra stations available to listen to is a bonus.
But DAB+ reception in cars or in the canyon-like streets of major cities is a major problem. Whereas FM may be subject to multi-path distortion or rapid variations in signal strength which can make reception quite noisy, DAB+ just drops out completely. One moment you have clear reception and the next you have nothing or maybe words or parts of words sputtering on and off. In this situation, you just switch off in disgust – or go back to FM, if you can. Of course, DAB+ radios normally do not even give you the option of listening to AM!
So DAB+ signal strength in many metropolitan locations is simply not good enough to generate good car radio sales in the future. Commercial Radio Australia may not be happy about that statement but it would difficult to argue against it. There is also a further impediment to acceptance of DAB+ in cars and that is that sound equipment in cars made over the last five years or more is so closely integrated that it is difficult, if not impossible, to upgrade to an after-market system, whether it is DAB+ or not. And if car manufacturers are aware of the poor reception of DAB+, why should they make any effort to change?
We have another reason to be critical of DAB+. We put a great deal of development work into the DAB+ tuner that we featured in the issues from October-December 2010 and which has been made available as a kit by Jaycar Electronics. That design potentially delivers the best sound quality that you can get from any DAB+ signal. If we had known that music stations would generally select such poor data bit rates, we would probably not have committed to all that design work which was a major investment on our part. Other organisations who have developed good-quality DAB+ products must feel exactly the same.