[cma-l] Digital Radio - some views

[Jaqui Devereux]

Dear all

Clive from Radio Verulam has kindly put this brief guide to digital 
radio platforms
together for us all, as a draft for any of you to add to and comment on:


I have attempted to put together a very short note on "digital" radio
to help anyone struggling with the concepts (i.e. judging by yesterday, 
everyone!).

It is NOT definitive and I am not an expert by any means!

I think my conclusions are that there will not sensibly be a digital
switch off of radio for decades. In one sense, that is enough for most
CR stations to know. Day to day running of the stations is rather more
important than something that probably won't happen within most
people's lifetime!

If I were the DCMS/OFCOM I would be pushing for a switch to DAB + for
national & regional services. It would mean everyone with an existing
DAB set will be disenfranchised after a few years so I would set up a
voucher system or similar where returning an existing DAB set to buy a
DAB + one would benefit from a discount (with Government plus
manufacturers contributing). Every week they don't do this more people
will buy DAB sets so there is also a need to persuade manufacturers to
make only DAB + sets from asap.

But the most promising technology is DRM and DRM+ so this should be
encouraged when it is fully available and, again, manufacturers should
be making universal sets asap. (And yes, DAB + sets won't work on DRM
either!)

Most likely Government response in my view? Head in sand for several
years...

regards,

Clive

DIGITAL RADIO

DAB – Eureka 147 development now 20 years old. Based on MP2 audio 
coding. Now looks (and sounds!) dated.

In order to squeeze more stations into the frequencies used both BBC and 
commercial broadcasters have lowered the bitrates used so quality is 
less than on FM and many are being broadcast in mono while they are in 
stereo on FM. BBC research originally suggested 256 kbs for high quality 
stereo but now broadcasts at 128 kbs (but Radio 3 at 190 kbs after 
complaints!)

DAB + system much more recent development (agreed 2006) using AAC+ 
encoding (same as iPod for example). Approximately 3 times more 
efficient than MP2, meaning more stations per multiplex and better 
quality (at higher bitrate). But DAB + is not backwards compatible so 
anyone (5 million plus!) with an existing DAB receiver will NOT be able 
to receive DAB + stations. New DAB + receivers will be able to receive 
the “old” DAB signals but these are not available and there is no move 
to make manufacturers switch to DAB + receivers...

DAB & DAB + still much more expensive and based on multiplexes so 
unsuitable for Community or Local radio.

DRM (Digital Radio Mondiale) is a digital system agreed in 2005 (?) 
designed for use on Short Wave, Medium Wave and Long Wave (frequencies 
below 30 Mhz). It is based on a single frequency transmitter (like 
analogue systems) so costs are likely to be more than for analogue 
systems (say, 10-20%) but not excessively so. A BBC lady told me that 
DRM “doesn't work” because the BBC's tests had shown problems using it 
at night time (anyone who has ever listened on SW or even MW will know 
propagation changes at night time so this should hardly be a surprise!).

DRM + is similar but for use in High Frequency bands (FM or DAB 
frequencies). Still under development so not likely to be agreed for 2/3 
years (say, 2011/12). Could be ideal for Community and Local Radio but 
this is still to be proved!

It would be possible to develop radio receivers which can receive 
everything (OFCOM suggested this would be called a “Universal” radio), 
perhaps in a similar timescale – let's say the first consumer ones would 
be available in 2012. They would be expensive, more like DAB or DRM 
receivers (£100-150 in today's money?). All that would be needed then 
would be for them to be made as kitchen radios, portables, car radios, 
clock radios etc etc and everyone in the country to buy them and throw 
away their old radios and we have Digital Switchover for Radio in....2070?


Clive Glover