[cma-l] MiniDAB

Wed Mar 9 14:24:51 GMT 2016

I don't understand these comments about number of channels and
interference.  I wonder if there is some old analogue/FM thinking going on?

DAB has the capability to transmit on the same channel without causing
interference (in fact delivering a significant gain in the overlap area).
It's called SFN - but it requires all the transmitters to carry the same
Mux content.

So for large metropolitan areas you could have one mux covering the centre,
and three or four relays in the suburbs - all on the same channel.  Use
AAC+ coding and it could easily deliver 30 services with pretty good audio
quality.   The alternative is not worth considering - 5 transmitters on
separate channels would deliver far too much capacity (150+ programme
services), and 5 separate muxes on same channel would deliver far too much
interference rendering it unusable.

Unless I'm missing your points...?

Glyn

On 9 March 2016 at 11:11, Two Lochs Radio <tlr at gairloch.co.uk> wrote:

> An orderly migration to DAB+ ought to be a priority, and ought to be
> mandatory for new services in my opinion. That would gradually release
> capacity on existing multiplexes, but of course their operators would be
> looking for more commercial services to raise revenue, not community
> services.
>
> The currently trialled model of mini-DAB multiplex should work in smaller
> towns and less densely served regions. In major metropolitan areas A good
> start for community would be a publicly funded DAB+ multiplex which could
> probably offer 24 channels at 48k AAC+ quality at affordable carriage costs
> using modern technology and a non-profit model. But DCMS would have to fidn
> the cash, and I guess the commercial operators might lobby heavily against
> it though.It seems to me that would have been a more productive use of some
> of the millions being put into local TV, but that's just a personal opinion.
>
> That could be supplemented by some mini DAB multiplexes for hyper-local
> stations - for example four low power co-channel multiplexes in N, S, E and
> W of a large metropolitan area, with reduced guarantees of freedom from
> interference at the margins.
>
> Alex
>
> On 09 March 2016 at 09:46 Tony Bailey <ravensound at pilgrimsound.co.uk>
> wrote:
>
>
> The thread is really about small scale DAB so: MiniDAB - it's a
> technically clever setup although as Phil points out will in some ways
> be less effective in metropolitan areas. London now has a total of six
> digital multiplexes using up the equivalent of nearly half the FM band
> in Band 3 without a single community station slot. There are probably
> 30 odd prospective CR licensees in the city and the sensible solution
> would be a city-wide single transmitter CR mux. MiniDAB would need too
> many channels to do the job, unless someone can come up with a narrow
> band version. Has there been a spectrum usage/ benefit analysis of
> small scale?
>
> Tony Bailey
>
> On 08/03/16 18:10, Phil Edmonds wrote:
>
> It's interesting to "compare and contrast" these small scale DAB
> trials with the "Access Radio" pilots.
>
> Hopefully I've got the time scales "more or less" right here (someone
> do please correct me if I'm wrong.)
>
> 2001 - Radio Authority sort applications from interested parties to
> take part in Access Radio trial.
>
> 2002 - Pilot stations launched "12 month" trial.
>
> 2003 onwards - numerous "extensions" of trial licences. Ultimately
> until 31st December 2005.
>
> 2003/4 Legislation for Community Radio proceeds.
>
> 2004 Full time Community Radio licences advertised.
>
> 2005 First "Community Radio Licenced" station launches.
>
> 2006 Most of the pilots commence full licence.
>
> 2006/7 'Round One' Community Radio licences launch.
>
>
> Between 2002 pilots starting and the opportunity for others to apply
> and start broadcasting under a Community Radio licence several years
> down the line there were many "interested parties" ready and waiting
> "biting at the bit" to get a licence and go "on-air".
>
> Sounding familiar with the situation today with interested parties
> with the small scale DAB?
>
> So I can see a perfectly reasonable argument for Ofcom to extend the
> trials.
>
> However I'd be asking for reassurances that just like the Access Radio
> pilots that the relevant "processes" needed to get licencing for
> others to apply to be "part of the party" is put in place while these
> extensions are in place. Logic dictates this must be the "general
> plan" unless Ofcom are just going to roll over a second extension.
>
> However this is were my analogy with the Access Radio pilots hits a
> road block. In areas with 'high demand', lets case study Greater
> Manchester here, not only did Ofcom find "space" for the two
> "incumbent" access radio pilot stations to stay on-air, but also
> numerous other "new comers" on FM.
>
> This probably won't be the case of multiple "interested parties" to
> operate DAB multiplexes in addition to the incumbent pilot.
>
> Having said that Greater Manchester is an unusual conurbation in such
> high density of "radio stations" in one urban conurbation. That's
> probably only equalled by the Greater London conurbation who, in the
> main, haven't even had the same bite of the "FM cherry" for community
> radio operators.
>
>
>
> On the other hand I could just argue to just get the nationals and
> regional's off FM in the majority of "mainland" UK were there is DAB
> equivalence, let the smaller Community and Commercial stations have
> higher TX powers on clear frequency allocations to give decent field
> strength in their core service areas and encourage receiver
> manufacturers to build sets that display the FM RDS station names in
> the same "station list" as the DAB stations for users to select from
> and everyone would be happy!
>
> Phil.
>
> --
> Local Reports at http://www.ravensound.pilgrimsound.co.uk
>
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-- 
Glyn Roylance - Principal Consultant
Associated Broadcast Consultants <http://www.a-bc.co.uk/>
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