03-07-2019, 07:40 AM
The odd thing is that early work on DAB showed a lot of promise. I remember going to a talk at the IEE some years ago where BBC Research showed a film about their DAB work. They had a equipped a coach with FM and DAB receivers and set up an experimental DAB TX in Birmingham. They drove the coach around Brum's tunnels and underpasses. DAB stayed rock solid except in the longest tunnels, FM was pretty horrendous.
That's the RF side. I don't know what got downgraded between the tests and start of service, or if for some reason the tests weren't representative of real life. I don't believe that BBC Research frigged the results. Perhaps it's a bit like the introduction of VHF FM in the 1950s, where the assumptions were wrong for hjow the service actually developed. For VHF FM the service was predicated on the use of outdoor aerials, just like TV. Needed more power and mixed polarisation to get it work well with portables. Should be posible to find the relevant reports on the BBC Research website.
The audio side is another matter. I think DAB was conceived with 256kb/s and MP2 data compression. I understand this is pretty good but as you push down the bit rate then MP2 is far from ideal. It was too soon for MP3, AAC or other data reduction which can give better results at lower bit rates.
So we're saddled with a half-a****d system. What's the betting that FM will outlast DAB? With internet now being an important platform for radio what's the real point of DAB?
That's the RF side. I don't know what got downgraded between the tests and start of service, or if for some reason the tests weren't representative of real life. I don't believe that BBC Research frigged the results. Perhaps it's a bit like the introduction of VHF FM in the 1950s, where the assumptions were wrong for hjow the service actually developed. For VHF FM the service was predicated on the use of outdoor aerials, just like TV. Needed more power and mixed polarisation to get it work well with portables. Should be posible to find the relevant reports on the BBC Research website.
The audio side is another matter. I think DAB was conceived with 256kb/s and MP2 data compression. I understand this is pretty good but as you push down the bit rate then MP2 is far from ideal. It was too soon for MP3, AAC or other data reduction which can give better results at lower bit rates.
So we're saddled with a half-a****d system. What's the betting that FM will outlast DAB? With internet now being an important platform for radio what's the real point of DAB?
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
