As new technology replaces old, how do we find out how many people are still using the old technology, and when is the right time to stop supporting old equipment?
That's one of the main issues facing those in charge of switching radio to digital. In Switzerland, a group comprising of public and commercial radio groups has proposed replacing FM with DAB+ by 2024.
The matter in the UK is not so clear cut. A decision on when digital radio switchover will occur has been deferred; the radio industry is first of all sorting out DAB coverage and looking to launch a second national DAB multiplex.
Although FM radio is still very healthy in the UK, there's evidence that listening on AM continues to decline. And reaction from listeners is a principal way of finding out how many are still listening - a method tried and tested when various BBC Local Radio stations trialled closedowns of their AM service two years ago. Interestingly, with the Droitwich BBC Radio 4 long wave (LW) transmitter site undergoing maintenance at the moment, there's been relatively little interest outside of the world of radio enthusiasts - and on a516digital, the biggest reaction has come from listeners in France and Belgium.
On the 15th May, a516digital received reports that RTÉ Radio 1 on 252 kHz LW was off air. A few posts scattered around the internet from users across the UK confirmed this. There was no mention on the usual transmitter information outlets from RTÉ or Irish transmitter company 2rn via internet and teletext. In fact, looking back, it's almost as if nothing ever happened. Rollback to previous occasions when the RTÉ long wave signal has been lost due to transmitter work or reduced power, and you get the distinct impression that in the past two years, there's been a noticeable drop in LW listeners - or those that do listen aren't the type to flock to the internet to complain. Incidentally, RTÉ Radio 1 can be received in the UK via internet radio or via Freesat, Sky or Virgin Media - and has the advantage of being more reliable and not susceptible to "noise" from various types of electronic equipment so common in homes today.
It seems AM, and especially LW for all but die-hard enthusiasts will die out long before any decision is made to fix a date for digital radio switchover in the UK. Broadcasters will be trying to figure out when the right time is to stop supporting AM radio.
The BBC finally updated its DAB webpage in the past week to show how it has expanded its DAB radio network in recent months.
Since February, new transmitters have been added at Aberdare, Bala, Deiniolen, Betwys-Y-Coed and Wrexham-Rhos improving DAB reception for households and motorists in North Wales. In Derbyshire, transmitters at Calver Peak and Birch Vale have gone live, improving reception in parts of the Peak District. And a transmitter serving Thetford in East Anglia is now in service.
Additional transmitters on local DAB multiplexes have gone into service in recent months. A transmitter at Boar's Hill expands coverage of the Oxfordshire multiplex, and a new transmitter at Daventry expands the Coventry multiplex eastwards, filling the gap left when the West Midlands regional DAB service ceased last year.
Tests continue in Derbyshire for the new Derbyshire local DAB multiplex. A test consisting of a carrier, but no radio stations has been observed on VHF block 10B over the past few days. Many DAB radios therefore ignore the tests until there's an actual radio station broadcasting.