Author Archives: radiohead

Raspberries, Steroids and Low Cost DAB


On the horizon there is a real possibility that digital radio broadcasting in the UK could become affordable….

TODROID-U3he picture on the right is of a small yet powerful Linux computer called the ODroid.  It was described yesterday by Martin James (Manager of Broadcast Radio) at Ofcom as “like a Raspberry Pi on steroids”.

It is smaller than a pack of playing cards, yet it is this hardware that they were using to demonstrate the potential of Low Cost DAB at Riverside House yesterday.   It seems incredible, but this diminutive device was being used to encode 6 audio streams into MP2 (the current codec of choice for DAB in the UK) and then multiplex them together into a DAB multiplex suitable to be fed to a Band III transmitter modulator.   Thus for around $65 plus some free open-source software it seems possible to produce a mux signal equivalent in many ways to that generated by professional DAB Mux equipment costing tens of thousands of pounds.

And it seemed pretty stable too.  Rashid Mustapha (low cost DAB guru at Ofcom) demonstrated the lack of impact by failing on of the programme streams (by pulling the plug!).  The other five streams on the Mux happily carried on – as demonstrated on a domestic DAB radio set alongside the demo equipment.

Of course more is needed to transmit DAB – not least a modulator (to turn the Mux bistream into a radio signal), an amplifier (to amplify!) a filter (to remove any sprogs generated in the amplification stage) and an antenna plus some kind of tall structure to mount it on.  All this does not come cheap, but then again, compared to the cost of carriage on existing commercial Mux’s, it is not expensive either.

Nor should we forget the cost of links – the important lines that get programme services from different stations to the little ODroid Mux box, and potentially a broad link from the output of the little Mux box up to the transmitter site.  Yet here too there are low cost alternatives to current approaches.  Trials indicate that the internet is stable enough for individual programme feeds.  And for the big link between Mux and transmitter there are affordable digital microwave links available.   Intruigingly also Ofcom hinted at the possibility of using on-channel repeaters.  This means the mux could be connected to a low power transmitter at a suitable host location (possibly one of the radio stations hosted on the Mux), and then this signal could be received, amplified and re-transmitted from a big hill giving wide area coverage.

Low cost DAB spectrum analyser

Spectrum Analyser showing the Low Cost DAB signal

There is still a long way to go.  The current stage is very much prototype.   The next stage is a trial next year for which Ofcom recently issued a consultation (see post below).

It will be interesting to see how this low-cost DAB concept develops, and how incumbent DAB Mux operators  will react.  Hopefully there is room in the UK Broadcast industry for both “Gold Plated” and “Low Cost” DAB.


Ofcom revises its invitation for applications for community radio services in the East of England


In a surprise move Ofcom today announced that it had revised its invitation for applications for community radio services in the East of England.

The change regards Southend-on-Sea where it had previously said there were no available FM frequencies for a new community radio service.  Apparently one of the main concerns was interference from a very high power transmitter in Lille, France, although potential applicants in the area say they have never noticed any French stations receivable on the FM dial in their area.

Funky SX logoThis is great news for (currently) internet-only station Funky SX who won £50,000 through ITV’s the People’s Millions to establish a youth-led urban and dance music radio station for Southend-on-Sea.


Ofcom consults on new short-term licences for small-scale DAB Trials


The wheels turn slow, but things seem to have started moving at Ofcom with regard to what they variously call either “Low-Cost DAB” or latterly “Small Scale DAB”.  One wonders if the new name is to pacify the incumbent DAB multiplex operators who surely must have been a bit jittery by the original “low cost” name?   Anyway Ofcom published today a consultation on  new short-term licences for small-scale DAB Trials.  Is that a trial of small-scale DAB, or a trial of DAB that is small in scale?   Generally the idea is to find a digital solution that addresses the needs to small-scale and community radio broadcasters in the UK.

Currently such broadcasters find it difficult to get on DAB due to the huge expense – resulting in a bizarre situation where there is demand, but many commercial Mux’s are running significantly below maximum capacity.  Cynics will say this is due to the lack of competition for DAB transmission services in the UK, although partly it is as a result of the structure of the DAB industry.   Also the technology requires a collection of radio services to be broadcast on one frequency instead of one service, one frequency like for FM.  Whilst this does not explain the expense (surely sharing transmission should reduce costs?), it does explain the need for “transmission middle-men” – the Mux operators.

The Ofcom trial, and others like the Total Broadcast DAB trial in Ireland have demonstrated that it is possible to provide DAB services for significantly lower cost that existing UK DAB Mux providers.

This consultation will give interested parties an opportunity to shape the future of DAB in the UK.  No doubt it will also give the DAB incumbents an opportunity to create obstacles to creating viable competition to their lucrative businesses!


CR station wins High Court battle to continue broadcasting


An interesting David & Goliath storey of how a CR station won a High Court battle to continue broadcasting here.   The judge Mr Justice Treacy said of the Ofcom decision:

“In my view it was unfair for the breach decision and the no extend decision to have been taken without conscientious engagement with the request for an oral hearing……I also consider that without such safeguards the decision is disproportionate.”

It will be interesting to see if this changes how other CR stations approach their key commitments, or how Ofcom deals with trangressions.


Ofcom invites applications for licences to provide community radio services in localities within the East of England


In a surprise move today, Ofcom  invited applications for licences to provide community radio services in localities within the East of England together with Northamptonshire and Milton Keynes.

It is not known if this tactic is an opportunistic way to bring more radio choice to the East of England a little earlier than expected, or a cynical way to further delay the invitations for London and the South East (originally planned “First half of 2014”).

What is obvious though is that Ofcom, maybe inspired by the recent Scottish referendum debate, has re-drawn the map of regions in Southern England compared to what it envisaged in the original Third Round licencing guidance.

Ofcom Community Radio Regioons Map - Eastern England

Ofcom has created a new Greater London region 10 (that should get people hot under the collar!) and the old Region 7 for London and South East now becomes Region 9 for South East minus London.   In fact this is not new – they did something similar when they invented a new West Midlands region for the invitation earlier this year.

What is less of a surprise is the usual Ofcom guidance notes for would-be applicants.  It reminds them of the limits on advertising.  It also advises on limits to frequency availability, but helpfully suggests that AM frequencies may (not will) be available.   Near the end it also lists some poor little commercial stations that need to be protected from the ravages of competition from Community Radio – entertainingly including Heart!

Full details available in the Ofcom Invitation of applications for community radio licences: EAST OF ENGLAND (WITH NORTHAMPTONSHIRE AND MILTON KEYNES)

Applications for community licences for these areas must be received by 5pm on 16 December 2014.  Associated Broadcast Consultants is expecting a busy time ahead – we advised a record number of applicants during the last invitation for the East and West Midlands.


“DAB is the Future” – so have another 12 years on your FM Licence!


Yesterday Ofcom published a statement detailing the extension of advertised or readvertised local commercial analogue radio licences from seven to 12 years – lending these stations a somewhat greater degree of certainty than Community Radio stations that only get 5 years at a time.

Implicitly they are saying the FM waveband will remain until at least 2026 and probably beyond.  Given the sheer quantity of analogue receivers in customers hands, and the average replacement cycle (surely 10 years plus) then this seems like a very pragmatic line to take.

It’s great news for those stations – they can continue on FM effectively as long as they like.  If DAB becomes mainstream in that time, no doubt they can just hand-back their FM licences – although they may think twice about freeing the band for unwelcome competition!

The full statement can be found on Ofcom’s website.


Ofcom FM/VHF Protection Ratios Illustrated


Ofcom are on the record stating that there is frequency congestion on the FM Broadcast band in many areas.  This can often cause frustration because to the layman it appears that there are plenty of unused frequencies on the dial.  The cause of this situation is the technical criteria that Ofcom use for their spectrum planning of this band.  There are many criteria, but in this post we focus on just one – the Protection Ratio, and in particular the co-channel (same channel) protection ratio.

It’s a bit of a dry subject, but has profound consequences.  Therefore we’ll use pictures and try and short-hand some of the technical language to make it more accessible.

Take by example our local Community Radio station – Bradley Stoke Radio (note we designed and commissioned their transmission system last year).  They broadcast with 25 watts on 103.4MHz from a low antenna attached to a community centre in North Bristol.   Their coverage area (the standard 54dBμV/m one that BBC and commercial stations use) is illustrated below – it’s that small green blob in the middle.


Click to Enlarge. Underlay map by

Now the cynics among you will probably ask why such a big map – perhaps we are trying to exaggerate how small their coverage is – but there is method in our madness – please read on.

The above-mentioned Ofcom technical criteria state (on page 12) that the co-channel protection ratio for stereo services is 45dB.  To the layman that’s just a number, but to a radio engineer they think “heck that means the interfering signal has to be 31623 times smaller than the wanted signal to avoid interference half the time!”.  Gut feel indicates it can’t be right, but Ofcom cannot plan their spectrum strategy on gut-feel – the figures are based on internationally-recognised recommendations published by the ITU (page 5 of this document).   Adding this factor on top of little Bradley Stoke Radio’s signal results in an interference area indicated below.


Click to enlarge. Underlay map by

That’s right – according to this protection ratio Bradley Stoke Radio’s lowly 25 watt transmitter effectively sterilises 103.4MHz across large swathes of south west England and south east Wales.  So in large areas from the southern edge of Birmingham, to Exeter, and Oxford to Cardiff it is not (apparently) possible to have another FM radio service on that channel.  This is borne-out by Ofcom’s actual frequency plan – only 11 transmitters on 103.4MHz across the entire UK.

UK Stations on 103.4MHz

UK Stations on 103.4MHz – Click to enlarge

This level of re-use is actually slightly above the national average of 9.3 (excluding the heavily under-utilised spectrum territory around 87.5-88.0MHz – presumably to ease the workload of RSL spectrum planning).

UK VHF/FM Frequency Re-use

UK FM channel re-use – Click to enlarge

To put that in context, each mobile phone network would probably have more than 50 20watt transmitters on the same frequency in Bristol alone and many hundreds across the same area of the UK.  However we are not comparing apples to apples there – the frequencies are different, and FM is an old analogue system that, in human terms, should be drawing its pension by now.   In contrast mobile phone networks are digital systems that have had over half a century extra human ingenuity in their development.  This is a major reason why Ofcom drives “re-farming” of spectrum from old to more spectrally efficient technologies (eg analogue to digital TV)

This is all caused by that 45dB protection ratio for FM.  It’s all too easy to stamp our feet and say “it must be wrong” – but as Scottie always said to Captain Kirk – “ye cannae change the laws of Physics“.  Nevertheless, there is a worthwhile goal here to achieve more listener choice and greater social gain – so could there be a third way?   Associated Broadcast Consultants think there could be – let’s outline a few possible approaches below:-

  1. Re-study the protection ratios.  We think this will not be a fruitful angle of approach.  Even with global warming, the laws of physics of radio propagation are unlikely to have changed over the last few decades.  True you could look at some of the assumptions (eg: that assumed receiving aerial height is 10m above ground level) – but in reality it could be difficult to get sufficient support to make this happen at ITU, and even if it were possible we’d probably all be pushing-up the daisies by the time the study finished!
  2. Band Re-plan.  An alternative approach is to re-plan the FM band to deliver a small amount of spectrum that is managed with lower protection ratios for use by stations at their own risk.  In practice this is not practical – too costly and disruptive to for wholesale frequency and power changes for a band/system with limited life.  Maybe if Radio 3 made an early exit from the FM band it could be an option to create a sub-band with tighter re-use of frequencies.
  3. Consider TSA instead of MCA – Many stations’ Target Service Area (TSA) is smaller than their Measured Coverage Area (MCA).  Therefore it seems rather a waste of spectrum to protect incumbent stations’ signals outside of their target area.  This approach could allow significantly denser packing of stations on the same channel.  Come to think of it, reduced protection may act as a gentle “nudge” to encourage incumbents to  transition to DAB should Ofcom want that.
  4. Review approaches of other regulators – There has been anecdotal evidence that other European regulators take a different approach to the ITU protection ratio recommendations (and other restrictions like the 10.7MHz image channel).  We are not aware of evidence of listeners in other countries complaining about FM interference any more than the UK.  Therefore we request Ofcom to consult their European colleagues and review what approaches to FM planning are taken in neighbouring countries.
  5. Pragmatic reduction in protection ratios – For example select a small number of stations that wish to have a power increase.  Carefully increase their power and see if there is any impact to the listen-ability of co-channel stations.  Most of those “interfered” stations will anyway be benefiting from increased protection since they came on-air because many will have alternative channels that could be used by listeners experiencing difficulties (eg DAB, satellite, DTV, mobile, internet…)

Associated Broadcast Consultants encourage Ofcom to consider options 3, 4 and 5 above. They are relatively small changes that should be within Ofcom’s power to change as part of its’ remit to efficiently manage the nation’s spectrum, and should not require primary legislation.

You are welcome to use the images and text in this post as long as you credit Associated Broadcast Consultants and give a link to this website.


Keep this Frequency Clear!


Real Radio Wales logo

Capital FM logo

Heart logo

The poor Heart listeners of North Wales have had a confusing time lately.  Their old Heart station has changed to Capital – not the kind of “More Music variety” that the average Heart listener likes!  But all is not lost because in the same area the old Real Radio has changed to Heart.  Confused – you won’t be after their slick marketing guys came up with some crafty communications to make everything clear.  They even avoid using the word “frequency” which is far too technical for their listeners to understand 😉

Phil Edmonds describes in more detail, with audio clips here.


Radio Stations are like Pubs!


Whilst reading the endless debate on Media UK about radio groups and takeovers it struck us that actually the Radio industry is much like the Drinks industry:

whitworthPhoto: Adam Bruderer

  • There are large breweries (radio groups), small breweries and plucky independents that run pubs (stations)
  • The industries follow fashions, and occasionally a pub needs a refurbishment or re-invention with the addition of mock beams, rows of old books or leather sofas (name, format, music etc).  Inevitably the regulars moan, but usually the update brings new punters.
  • People (especially “radio people”) are fiercely loyal about their pub/radio station preference – it’s a head not heart decision that no amount of debate can change.


Next we started wondering about what kind of pub each station would be – for fun we list some below:

Wetherspoons (Capital, Kiss…) Packed full of twenty-somethings drinking lager out of the bottle and downing Jagermeisters

Harvester (Heart, Smooth…) The safe bet where people go for breaded mushrooms or a prawn cocktail washed down by a nice glass of Chardonnay.

Yates’s Wine Lodge (Real Radio, GWR, BRMB, Piccadilly…) Although once very popular, now looking a bit run down and shabby and need of a refurb/reinvention

Old House at Home (BBC local) Patterned carpets and aging pine kitchen chairs.  Where people go for a good old gossip and chin-wag over a game of cribbage.

Busy Freehold Pub (Jackie, Sunshine…) Great atmosphere, friendly service, good range of well kept beers and good honest pub grub

Brewery Trip (Community radio) Where enthusiasts go to find out how beer is made and talk to people about making beer.  They do home brew with varying degrees of success.  Breweries have a limited distribution network (coverage) and are limited to 50% of their revenues selling beer.  They survive by begging and holding cheese and wine evenings (OK we made that last bit up!)

Village Local (Radio Caroline) Full of character with wonky old beams and an open fire.  Normally frequented by aging men with beards talking about the good old days.

Boose Cruise (Pandora, Spotify) Hire a van, drive abroad and load up with tons of whatever you want, siphoning profits and taxes away from the UK.

Please don’t take offence – it’s only a bit of fun.  See you in the Village Local for a pint!


East and West Midlands – Attention! They are not joking!


Today 1 April 2014 Ofcom invited applications for the third round of Community Radio licences in the East and West Midlands. Despite the date they are not joking!  The Ofcom definition of East and West Midlands is best shown in the map in their document:

Ofcom East West Midlands

As usual there is the list of areas where they will not accept applications due to “no suitable FM frequencies available” – these are:

  • City of Birmingham
  • Solihull
  • City of Coventry
  • Derby
  • Nottinghamshire (with the exception of Newark on Trent)
  • Nottingham
  • Lincoln
  • Leicestershire
  • Leicester

And the Black Country gets special treatment as follows:

Applicants wishing to provide a service to a locality within any of the following
districts of the West Midlands – Dudley, Sandwell, Walsall or Wolverhampton –
should note that there is only one suitable FM frequency available for a service in
these areas (in other words, FM applicants from any of these areas will be competing
with each other for the single available frequency).

The closing date for applications is 5.00 pm on Tuesday 24 June 2014. A non-refundable fee of £600 will be payable for each application submitted and considered. Full details here.