The situation in the UK where DAB has been in use for some time appears to be dire as far as analog FM stations go. Latest policy was that all but low power FM (I presume that means like our local community type stations)will be shut down fairly soon. Reports seem to indicate general dissatisfaction with the DAB quality. Hardly surprising with the all or nothing digital signal and when the bit rate is 'economised' to allow more channels on the one carrier.
Here in Australia, DAB has officially been in operation for about 6 months. Our version is DAB+ and not the same as the UK. (Here we go with incompatibility).Like digital TV, there's no general consumer interest; it's still in the geek/nerd toy stage. There is at this stage no plan to turn off any analog radio "for many years to come".
Given the distances between population centres in Australia, medium wave AM is still highly regarded in rural areas because it travels whereas VHF FM is dependent on topography. Given DAB is up in Band 3 (roughly 200MHz) I would expect even shorter distances than FM. And, of course unlike AM or FM where the reception just gets noisier (but still useable) with a weakening signal, DAB leaves you with nothing under the same circumstances. So, I think analog is likely to survive in rural areas after it is eventually shut down in the cities.
One serious threat to AM stations though, is Sydney where most of the transmitters are in what is now highly sought after area for development (i.e. ugly blocks of Soviet style flats). Given nothing can be built within about 250m of the towers in case they collapse, there is pressure to move them. One could be cynical and see this as an excuse to shut them down altogether.
Also, consider the changing demographic of listeners. We now have a generation that don't listen to AM and once the baby boomer generation has gone AM is sure to go with it. Generation Y while it grew up after FM was introduced here is making the switch to mp3 players and internet downloads, so I don't think they'll miss it too much. How often do you see a Gen Y or younger person with a portable radio now?
As for receiving DAB on existing radios, that's an important issue as I collect and restore ancient valve radios. The only way to do it is simply feed the audio output of a DAB receiver into an AM or FM modulator. But while an extra box is tolerable with digital TV, it would be a complete pain with portable sets. The tuning in of stations would still have to be done on the DAB receiver. Whichever way you look at it, the charm of tuning in stations with a variable condenser in your old valve radio will be gone.
