[cma-l] DAB trials
Ian Hickling
transplanfm at hotmail.com
Mon Mar 9 13:18:15 GMT 2015
My apologies if I misinterpreted your words Phil.By "..... Ofcom have 'sourced' a handful of 100 watt models....." I visualised locating a redundant batch of units on someone's storage rack.I asked the relevant Ofcom engineers about manufacturers of all the hardware required for Band III DAB because we are in contact with UK companies who do precisely that and the response was - "I think you'll find we are already talking to them".Hence what I previously wrote:".....transmitters for the project will be produced specifically by a UK manufacturer already producing similar equipment for existing broadcasters......"All very cloak-and-dagger - I love it!Ian
Date: Mon, 9 Mar 2015 12:27:36 +0000
From: connect at catlake.uk
To: cma-l at mailman.commedia.org.uk
Subject: Re: [cma-l] DAB trials
We've seen them Phil. They do exist.
Regards,
Cat Lake
Social Technologist, Writer & Broadcaster
Tel: 0333 37 00 250 • Mobile: 07973 400 423On-line: www.catlake.uk • Twitter • Facebook
On 9 March 2015 at 10:51, Fantasy Radio Office <office at fantasyradio.co.uk> wrote:
Thanks for your response Ian, but with respect, that's exactly what
I said - Ofcom have 'sourced' suitable transmitters. Whether they've
actually been built yet is of no consequence. I wouldn't expect
there to be ten units sitting on a shelf just waiting to be
delivered.
I hope the trials prove to be of benefit to the industry.
Phil Dawson
FANTASY RADIO 97FM
Devizes ,
Wiltshire
On 09/03/2015 09:27, Ian Hickling
wrote:
Not so I'm afraid Phil.
The information that we have suggests that transmitters for the project will
be produced specifically by a UK manufacturer already
producing similar equipment for existing broadcasters.
Ian
------------------------------------------------
> Date: Sun, 8 Mar 2015 18:36:25 +0000
> From: office at fantasyradio.co.uk
> To: cma-l at mailman.commedia.org.uk
> Subject: [cma-l] DAB trials
>
> Whilst we're delving deeply into the theory of RF
propogation, I suggest
> there could be another reason for Ofcom's suggesting
100 watts. Clearly,
> to acheive 10km radius at 220MHz, you'll need more
power than 5km at
> 100MHz. So, perhaps Ofcom have 'sourced' a handful of
100 watt models,
> which will be OK for this trial, which is all
guesswork anyway.... It
> has to be, as there are so many unknown quantities.
>
> Most importantly, whatever comes of this trial, it'll
be an awful lot of
> work for a handful of people. The most important
consideration must be
> 'how does this affect the listener?' and how will it
benefit our
> station? Probably the most overlooked questions in
all of this debate.
>
>
> Phil Dawson
> FANTASY RADIO 97FM
> Devizes ,
> Wiltshire
>
>
> On 08/03/2015 16:21,
cma-l-request at mailman.commedia.org.uk wrote:
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> > Today's Topics:
> >
> > 1. Re: Ofcom announces trials to help small
stations join
> > digitalradio - 100w limit (Tony Bailey)
> >
> >
> >
----------------------------------------------------------------------
> >
> > Message: 1
> > Date: Sun, 08 Mar 2015 15:58:21 +0000
> > From: Tony Bailey
<ravensound at pilgrimsound.co.uk>
> > To: cma-l at mailman.commedia.org.uk
> > Subject: Re: [cma-l] Ofcom announces trials to
help small stations
> > join digitalradio - 100w limit
> > Message-ID:
<54FC719D.6080100 at pilgrimsound.co.uk>
> > Content-Type: text/plain; charset="iso-8859-1";
Format="flowed"
> >
> > Ofcom states that the coverage limit is set at
40% of the "corresponding
> > local DAB multiplex area" and that a practical
limit of 100 W ERP "may
> > achieve a service area of approximately 10 km
radius". A synchronised
> > two tx (not repeater) system would be spaced at
no more than 15 km
> > apart. As pointed out below, this has to based
on a practical antenna
> > situation to have any relevance.
> >
> > Tony Bailey
> >
> > On 08/03/15 14:01, Ian Hickling wrote:
> >> It seem there's a lot of second-guessing
going on here from people who
> >> may know a lot about administration and
encoding but possibly not so
> >> about the black magic that is RF
propagation.
> >> There's no point in trying to relate 100W
ERP to 5km for Band III DAB
> >> - just as it's equally irrelevant to relate
25W with FM to 5km - sorry.
> >> Topography, geology, refraction, refraction,
foliation, antenna
> >> efficiency and launch conditions have far
too large an influence.
> >> In terms of propagated signal transit,
there's not a huge difference
> >> in practical terms between FM at say 100 MHz
and DAB at 200 MHz when
> >> you take into account antenna size,
efficiency, reflection and refraction.
> >> Because of the difference between
demodulation formats, a receiver
> >> can tolerate a much lower signal level on
DAB than on FM to resolve an
> >> acceptable audio service.
> >> This was originally proposed at 20dB from
the point of view of
> >> transmitted power but then revised to 10dB -
meaning that a DAB
> >> transmitter in Band III would need one tenth
of the ERP of an FM
> >> transmitter in Band II to achieve the same
audience.
> >> Hence it is puzzling why Ofcom has set so
high a required signal level
> >> for a DAB service area of the order of
72dBuV/m as opposed to 54
> >> dBuV/m for FM.
> >> Beware - there is a distinct difference
between a Power Decibel in
> >> transmission and a Voltage Decibel in
reception!
> >>
> >> Let's not invoke DAB+ and DRM - Ofcom
specifically rules them out in
> >> 2.30 and 2.32
> >>
> >> Yes, Block 5A would be ideal as it's
relatively clear, allocated and
> >> accessible to modern receivers - but Ofcom
apparently doesn't accept
> >> that as it hasn't headed straight for it.
> >>
> >> As I've protested many times, there is
technically nothing at all to
> >> prevent a standalone transmitter radiating a
single programme stream
> >> to serve a discrete area either on DAB, DAB+
or DRM as far as I'm
> >> aware. If I'm wrong I'd appreciate the exact
reasons why.
> >>
> >> Looking at only the RF component in the
transmission chain, several UK
> >> manufacturers could offer a 2U Band III 300W
unit at around ?2000 if
> >> the demand were high enough - no real cost
differences from today's
> >> Band II units.
> >>
> >> Let's not get distracted - the encoding is
software-defined - the
> >> actual RF transmitter is not!
> >>
> >> Ian
> >>
> >>
------------------------------------------------------------------------
> >> Date: Sun, 8 Mar 2015 11:13:25 +0000
> >> Subject: Re: [cma-l] Ofcom announces trials
to help small stations
> >> join digitalradio - 100w limit
> >> From: alan.coote at 5digital.co.uk
> >> To: tlr at gairloch.co.uk;
transplanfm at hotmail.com; info at a-bc.co.uk
> >> CC: cma-l at mailman.commedia.org.uk
> >>
> >> I can't help thinking that someone at Ofcom
ran the simulations and
> >> came up with 100W = 5km radius.
> >>
> >> Therefore if small scale DAB became a
reality it wouldn't annoy Radio
> >> Centre too much (they'd still complain as
that's their mentality) and
> >> at worst secondary legislation could make it
happen.
> >>
> >> Kind Regards
> >>
> >> Alan
> >>
> >>
> >> Hear Alan Every Week on Let's Talk Business
The UK's Premier Radio
> >> Programme For Current and Future
Entrepreneurs - Now Broadcast To Over
> >> 5 Million People
<http://www.letstalkbusinessonline.com/>
> >>
> >>
> >> From: "tlr at gairloch.co.uk
<mailto:tlr at gairloch.co.uk>"
> >> <tlr at gairloch.co.uk
<mailto:tlr at gairloch.co.uk>>
> >> Reply-To: "tlr at gairloch.co.uk
<mailto:tlr at gairloch.co.uk>"
> >> <tlr at gairloch.co.uk
<mailto:tlr at gairloch.co.uk>>
> >> Date: Sunday, 8 March 2015 00:45
> >> To: "transplanfm at hotmail.com
<mailto:transplanfm at hotmail.com>"
> >> <transplanfm at hotmail.com
<mailto:transplanfm at hotmail.com>>, Associated
> >> Consultants <info at a-bc.co.uk
<mailto:info at a-bc.co.uk>>
> >> Cc: "cma-l at mailman.commedia.org.uk
> >>
<mailto:cma-l at mailman.commedia.org.uk>"
<cma-l at mailman.commedia.org.uk
> >>
<mailto:cma-l at mailman.commedia.org.uk>>
> >> Subject: Re: [cma-l] Ofcom announces trials
to help small stations
> >> join digitalradio - 100w limit
> >>
> >> I simplistically presumed they settled on
the 100W suggested limit on
> >> the basis that at the Band III frequencies
of DAB it would give
> >> roughly the same coverage area (at
58dBuV/99%) as 25W on Band II (at
> >> 54dBuV/90%).
> >> NB the average *local* DAB multiplex power
is 1.3kW, not 2kW, but of
> >> course they tend to be from sites with much
higher antennas than
> >> economically available to community
stations, so the chances are the
> >> 100W represents an even tinier coverage area
in comparison to current
> >> local multiplexes than might appear at first
sight from a simple
> >> comparison of powers. But I can see it is
much easier for Ofcom to
> >> control the allowed power than to get into
arguments over exact
> >> percentages of area covered. Maybe 500W
would have been more realistic
> >> if they wanted to take that simplistic
approach, with a lower limit
> >> applied in the few cases where 500W coud
cause difficulties.
> >> (I guess there is also the question that
Ofcom is paying for the
> >> transmitters in the trial, and a band III
amplifier running at , say,
> >> 250W is a lot more expensive than a 50W one,
especially if one uses
> >> the technique of greatly underrunning a much
higher power design to
> >> help achieve the necessary linearity.).
> >> Seems to me that block 5A, (currently
unused, but allocated for local
> >> DAB) could be used as a UK-wide frequency
block for terrain limited
> >> single station services up to 500W to deal
with all the areas where
> >> there is a low density of local stations (ie
only one within the
> >> interference range of a 500W TX) and it
could be done tomorrow,
> >> without any fancy trials or risk of
interference, clearing out one
> >> whole tier of demand without any fuss,
leaving trials and more
> >> complicated sharing and co-channel planning
issues to be threshed out
> >> over time in the other seven frequency
blocks allocated to local
> >> ensembles in areas of more dense demand.
It's also much lower in
> >> frequency than the other blocks, which
reduces the demands on the
> >> low-cost software defined transmitter.
> >> Alex
> >>
> >> On 25 February 2015 at 13:04 Associated
Broadcast Consultants
> >> <info at a-bc.co.uk
<mailto:info at a-bc.co.uk>> wrote:
> >>
> >> We challenged the 100w limit in the
consultation - suggesting that
> >> the "no greater than 40% of the local
commercial Mux area" was an
> >> adequate limit. 100w is roughly 5% of the
average existing DAB
> >> transmitter power, so presuming community
stations don't deploy
> >> their DAB transmitters using tethered
balloons or satellites etc
> >> they unlikely ever to get near 40% unless
they deploy multiple
> >> numbers of transmitters (thus undermining
the low-cost aim).
> >> The standard consultation deflection
response was invoked (ie:
> >> address a different question) - stating that
"it is not
> >> necessarily the case that allowing a higher
power will in all
> >> cases reduce the number of transmitters
needed". We never said it
> >> would in all cases, but were suggesting that
by removing the 100w
> >> cap you retain some flexibility when it
/would/ make a difference
> >> in some cases! Unfortunately though,
consultations are single shot
> >> - no possibility to clarify the point or
challenge the response.
> >> I think we can all imagine the real
(unstated) reason why they are
> >> limiting it to 100 watts ;-)
> >> Don't get me wrong - 100w at 200MHz can
still provide useful
> >> coverage if planned correctly (other DAB
coverage planning
> >> services are available!), but in some cases
more may be required.
> >> Otherwise we risk repeating the same problem
that analogue CR has
> >> - the paltry standard 25w power is often
inadequate and quite
> >> literally blasted off the dial by much
stronger commercial and BBC
> >> signals. And this problem is even worse with
DAB (for technical
> >> reasons that I will not go into here).
> >> Glyn
> >> --
> >> Glyn Roylance - Principal Consultant
> >> Associated Broadcast Consultants
<http://www.a-bc.co.uk/>
> >>
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