I suppose this contribution would come under the heading "discuss general technical topics".

This refers to the UK's DAB service, and def. NOT to satellite radio as in say the US. I understand this has different problems unique to that partic. format/platform.

I trawled the government site "Of-com" trying to find why results from DAB radio were so bad out in the real world, and I came up with the reason why DAB is jocularly called "Distorted Audio Broadcasting".

The sampling rate of cd, the first available digital sound to domestic users is 44.1Ksamples/sec. This means the voltage of the analog audio waveform is measured 44.1 thousand times a second, and a digital 16-bit number raised each time. This achieves audio bandwidth 20Hz. to 20KHz, well wider than most people's hearing. The signal/noise ratio is so good a dynamic range (quietist to loudest sound) of around 90db. obtains, which is excellent, lots better than LP records or FM broadcasts. A combined development between Philips and Sony. (I have considerably simplified the above; it's much more complicated than that).

This makes the results from DAB er... disappointing to say the least. The sampling rate quoted on Of-com's site, is only 24Ksamples/sec. at the so-called 'half-rate coding'.The bit rate is only 128Kbit/sec., at best, when everyone says 190Kbit/sec. is required for half-decent quality. AND there is provision for only 96Kbit/sec!!! So the baseband audio has to be limited to only 11.25KHz. NOT GOOD when Philips/Sony get 20KHz. from a system which was born in 1988! On top of this, while cd is not mutilated by compression, DAB has a Mpeg-g2 compression built in. But it actually gets worse...

The UK DAB is sent out on band III VHF around 222 to 225MHz. But the power is very much lower than the more penetrating frequencies of 88 to 108MHz used by FM broadcasts. So we have a 'double-whammy' degradation here. In other countries the L-band of around 1.4 GHZ is used which it is said, is actually worse than our already awful system.

Because of low power, it is advised that external aerials be used to maintain a strong signal. So what happens when you're on the move as in a car? Unlike satellite broadcast radio, there is considerable signal variation in band III due to all sorts of reasons, dead-spots, reflections off hills and big buildings etc.

I hope someone from the Of-com dept. reads this...
IF YOU CLOSE DOWN THE FM TRANSMITTERS, THERE WILL BE THE BIGGEST HOWL OF PROTEST THERE HAS EVER BEEN, ESPECIALLY FROM CAR DRIVERS. It will be a political blunder worse than Lady Thatcher's change to the rating system/council tax, called poll-tax. Don't ever say you weren't warned...
Leedsman.
Here's a straightforward site -- http://www.stevelarkins.freeuk.com/dab-reception.htm which you might find interesting.
Also, Google -- "dab problems". Now there's an eye opener!
Further information: There has been a better codec/format called DAB+ around now for a couple of years or so, and is being adopted by some countries, notably Australia. Now, it's impossible to say if this DAB+ really is better, but whether it is or not, it is imcompatible with the DAB being broadcast in UK now. Your present DAB radio CANNOT be altered except in one case needing a factory refit. There is a plethora of different data codecs (like a format) in different countries, even in the EU, so there is no guarantee your portable UK radio will work outside UK. Also DAB radios are fearsomely power-greedy, flattening the batteries in portables in about an hour.