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How is small-scale DAB changing the radio landscape?

What started as a pilot three years ago is poised to enter regular service. But how is small-scale DAB changing the radio landscape?

On Thursday, a call for expressions of interest from potential multiplex operators comes to an end.

The responses received by regulator Ofcom will give a indication of how the industry sees demand for small-scale DAB and where in the UK listeners might be able to look forward to receiving additional radio stations.

Small-scale DAB, a cheaper way of distributing digital radio across localised coverage areas, using open source software, pioneered by Ofcom engineer Rash Mustapha, began as a trial in ten locations in 2015. Legislation enabling the creation of further small-scale multiplexes across the UK received Royal Assent in 2017.

As the FM band fills up and stations eye up a digital future, small-scale DAB is seen as a future platform for community radio stations as well as niche stations that haven't been able to afford a slot on the existing wide coverage multiplexes. From 24 hour weather stations, to stations dedicated to jazz, country, soul and vintage music, small-scale DAB has grown to offer something very different from the output of mainstream commercial broadcasters.

But is there a need for small-scale DAB to expand, given the number of other existing multiplexes and services out there? a516digital editor Mike Manning asked Ash Elford, who secured a pilot licence for Portmouth's small-scale DAB multiplex and is helping other small-scale operators, for an industry view. The response was optimistic:
"Small-scale DAB can be very affordable for broadcasters, especially when you consider that broadcasting on all ten existing small-scale DAB multiplexes would still be cheaper than the ratecard fee for most local DAB multiplexes, yet would yield potential total population coverage of nearly four million adults."

His multiplex, operating under the name "Solent Wireless" has seen a steady demand for broadcast capacity. So much that it, and other small-scale DAB multiplexes have led the UK's ongoing switch to the newer DAB+ standard, which allows more stations to broadcast per multiplex, moving ahead of traditional broadcasters who continue with the older standard. I ask how many stations could fit on a small-scale multiplex.
"From the moment Ofcom awarded our licence to today, we have always had more services asking for capacity than we can accommodate. There has been a steady stream of stations and potential stations getting in touch, and it's great to see that there is still a lot of enthusiasm from broadcasters that want to broadcast!

"The Portsmouth DAB multiplex has been making use of DAB+ longer than any other multiplex in the UK, something I am very proud of. We've never forced our existing MP2 DAB services to switch to DAB+, it's always been their own decision to make, and that's three of our twenty stations are still broadcasting in MP2 DAB. Currently, even though there is capacity for expansion, we're limited to twenty services."

But what of the risk to audio quality if too many stations share the same bandwidth? And are smart speakers threatening traditional platforms?

"I don't believe DAB is losing ground to anything because of sound quality issues. Audio purists probably never used DAB in the first place. I think where smart speakers post a threat to DAB is through convenience of use. So that's why I've been keen to push stations to provide good quality DLS, provide slideshow [e.g. images such as album art] and ensure our coverage is as good as it can be. We have an additional transmitter coming online in the next month to help improve indoor coverage. I believe it is possible for DAB and smart speakers to coexist. "

Once Ofcom has completed its call for expressions of interest, it will digest the responses and make further decisions about how small-scale DAB can move beyond the current ten trial multiplexes, to a service that can reach millions more listeners across the UK, after the Government introduces the necessary secondary legislation.

A cheaper "gateway" to DAB for niche stations, and an opportunity to provide listeners with more music variety beyond mainstream pop: small-scale DAB may provide a welcome boost to digital radio.