[cma-l] MiniDAB

Wed Mar 9 17:07:48 GMT 2016

Quite so Glyn - you've put it more concisely than I was going to.As regards available capacity, can I point out that Digital Terrestrial Radio - commonly referred to generically as "DAB" - has the potential use of the previous CCIR TV channels 5 to 13 in Band III between approximately 174 and 240 MHz offering 41 "SFN" channels - of which the UK is currently only using 10, - 10B, 10C, 10D, 11B, 11C, 11D, 12A, 12B, 12C. 12D for major services and another 3 - 7D, 8A and 9A for the 10 trial muxes. (Source - Ofcom TXParams - updated 19 February)So - quite a bit of space for expansion?

Ian HicklingPartnerOffice: 016 3557 8435  (07h to 22h GTS)Car: 075 3098 0115 (only responds when driving)6 Horn Street, Compton, NEWBURY, RG20 6QS

Date: Wed, 9 Mar 2016 14:24:51 +0000
From: info at a-bc.co.uk
To: cma-l at mailman.commedia.org.uk
Subject: Re: [cma-l] MiniDAB

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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