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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.<br>
<br>
I hope the trials prove to be of benefit to the industry. <br>
<br>
Phil Dawson<br>
FANTASY RADIO 97FM<br>
Devizes ,<br>
Wiltshire<br>
<br>
<div class="moz-cite-prefix">On 09/03/2015 09:27, Ian Hickling
wrote:<br>
</div>
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<div dir="ltr">Not so I'm afraid Phil.
<div>The information that we have suggests that <span
style="font-size: 12pt;">transmitters for the project will
be produced specifically by a UK manufacturer already
producing similar equipment for existing broadcasters.</span></div>
<div><span style="font-size: 12pt;">Ian</span></div>
<div><span style="font-size: 12pt;"><br>
</span></div>
<div><span style="font-size: 12pt;">------------------------------------------------</span></div>
<div>
<div><br>
<div>> Date: Sun, 8 Mar 2015 18:36:25 +0000<br>
> From: <a class="moz-txt-link-abbreviated" href="mailto:office@fantasyradio.co.uk">office@fantasyradio.co.uk</a><br>
> To: <a class="moz-txt-link-abbreviated" href="mailto:cma-l@mailman.commedia.org.uk">cma-l@mailman.commedia.org.uk</a><br>
> Subject: [cma-l] DAB trials<br>
> <br>
> Whilst we're delving deeply into the theory of RF
propogation, I suggest <br>
> there could be another reason for Ofcom's suggesting
100 watts. Clearly, <br>
> to acheive 10km radius at 220MHz, you'll need more
power than 5km at <br>
> 100MHz. So, perhaps Ofcom have 'sourced' a handful of
100 watt models, <br>
> which will be OK for this trial, which is all
guesswork anyway.... It <br>
> has to be, as there are so many unknown quantities.<br>
> <br>
> Most importantly, whatever comes of this trial, it'll
be an awful lot of <br>
> work for a handful of people. The most important
consideration must be <br>
> 'how does this affect the listener?' and how will it
benefit our <br>
> station? Probably the most overlooked questions in
all of this debate.<br>
> <br>
> <br>
> Phil Dawson<br>
> FANTASY RADIO 97FM<br>
> Devizes ,<br>
> Wiltshire<br>
> <br>
> <br>
> On 08/03/2015 16:21,
<a class="moz-txt-link-abbreviated" href="mailto:cma-l-request@mailman.commedia.org.uk">cma-l-request@mailman.commedia.org.uk</a> wrote:<br>
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> ><br>
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> > Today's Topics:<br>
> ><br>
> > 1. Re: Ofcom announces trials to help small
stations join<br>
> > digitalradio - 100w limit (Tony Bailey)<br>
> ><br>
> ><br>
> >
----------------------------------------------------------------------<br>
> ><br>
> > Message: 1<br>
> > Date: Sun, 08 Mar 2015 15:58:21 +0000<br>
> > From: Tony Bailey
<a class="moz-txt-link-rfc2396E" href="mailto:ravensound@pilgrimsound.co.uk"><ravensound@pilgrimsound.co.uk></a><br>
> > To: <a class="moz-txt-link-abbreviated" href="mailto:cma-l@mailman.commedia.org.uk">cma-l@mailman.commedia.org.uk</a><br>
> > Subject: Re: [cma-l] Ofcom announces trials to
help small stations<br>
> > join digitalradio - 100w limit<br>
> > Message-ID:
<a class="moz-txt-link-rfc2396E" href="mailto:54FC719D.6080100@pilgrimsound.co.uk"><54FC719D.6080100@pilgrimsound.co.uk></a><br>
> > Content-Type: text/plain; charset="iso-8859-1";
Format="flowed"<br>
> ><br>
> > Ofcom states that the coverage limit is set at
40% of the "corresponding<br>
> > local DAB multiplex area" and that a practical
limit of 100 W ERP "may<br>
> > achieve a service area of approximately 10 km
radius". A synchronised<br>
> > two tx (not repeater) system would be spaced at
no more than 15 km<br>
> > apart. As pointed out below, this has to based
on a practical antenna<br>
> > situation to have any relevance.<br>
> ><br>
> > Tony Bailey<br>
> ><br>
> > On 08/03/15 14:01, Ian Hickling wrote:<br>
> >> It seem there's a lot of second-guessing
going on here from people who<br>
> >> may know a lot about administration and
encoding but possibly not so<br>
> >> about the black magic that is RF
propagation.<br>
> >> There's no point in trying to relate 100W
ERP to 5km for Band III DAB<br>
> >> - just as it's equally irrelevant to relate
25W with FM to 5km - sorry.<br>
> >> Topography, geology, refraction, refraction,
foliation, antenna<br>
> >> efficiency and launch conditions have far
too large an influence.<br>
> >> In terms of propagated signal transit,
there's not a huge difference<br>
> >> in practical terms between FM at say 100 MHz
and DAB at 200 MHz when<br>
> >> you take into account antenna size,
efficiency, reflection and refraction.<br>
> >> Because of the difference between
demodulation formats, a receiver<br>
> >> can tolerate a much lower signal level on
DAB than on FM to resolve an<br>
> >> acceptable audio service.<br>
> >> This was originally proposed at 20dB from
the point of view of<br>
> >> transmitted power but then revised to 10dB -
meaning that a DAB<br>
> >> transmitter in Band III would need one tenth
of the ERP of an FM<br>
> >> transmitter in Band II to achieve the same
audience.<br>
> >> Hence it is puzzling why Ofcom has set so
high a required signal level<br>
> >> for a DAB service area of the order of
72dBuV/m as opposed to 54<br>
> >> dBuV/m for FM.<br>
> >> Beware - there is a distinct difference
between a Power Decibel in<br>
> >> transmission and a Voltage Decibel in
reception!<br>
> >><br>
> >> Let's not invoke DAB+ and DRM - Ofcom
specifically rules them out in<br>
> >> 2.30 and 2.32<br>
> >><br>
> >> Yes, Block 5A would be ideal as it's
relatively clear, allocated and<br>
> >> accessible to modern receivers - but Ofcom
apparently doesn't accept<br>
> >> that as it hasn't headed straight for it.<br>
> >><br>
> >> As I've protested many times, there is
technically nothing at all to<br>
> >> prevent a standalone transmitter radiating a
single programme stream<br>
> >> to serve a discrete area either on DAB, DAB+
or DRM as far as I'm<br>
> >> aware. If I'm wrong I'd appreciate the exact
reasons why.<br>
> >><br>
> >> Looking at only the RF component in the
transmission chain, several UK<br>
> >> manufacturers could offer a 2U Band III 300W
unit at around ?2000 if<br>
> >> the demand were high enough - no real cost
differences from today's<br>
> >> Band II units.<br>
> >><br>
> >> Let's not get distracted - the encoding is
software-defined - the<br>
> >> actual RF transmitter is not!<br>
> >><br>
> >> Ian<br>
> >><br>
> >>
------------------------------------------------------------------------<br>
> >> Date: Sun, 8 Mar 2015 11:13:25 +0000<br>
> >> Subject: Re: [cma-l] Ofcom announces trials
to help small stations<br>
> >> join digitalradio - 100w limit<br>
> >> From: <a class="moz-txt-link-abbreviated" href="mailto:alan.coote@5digital.co.uk">alan.coote@5digital.co.uk</a><br>
> >> To: <a class="moz-txt-link-abbreviated" href="mailto:tlr@gairloch.co.uk">tlr@gairloch.co.uk</a>;
<a class="moz-txt-link-abbreviated" href="mailto:transplanfm@hotmail.com">transplanfm@hotmail.com</a>; <a class="moz-txt-link-abbreviated" href="mailto:info@a-bc.co.uk">info@a-bc.co.uk</a><br>
> >> CC: <a class="moz-txt-link-abbreviated" href="mailto:cma-l@mailman.commedia.org.uk">cma-l@mailman.commedia.org.uk</a><br>
> >><br>
> >> I can't help thinking that someone at Ofcom
ran the simulations and<br>
> >> came up with 100W = 5km radius.<br>
> >><br>
> >> Therefore if small scale DAB became a
reality it wouldn't annoy Radio<br>
> >> Centre too much (they'd still complain as
that's their mentality) and<br>
> >> at worst secondary legislation could make it
happen.<br>
> >><br>
> >> Kind Regards<br>
> >><br>
> >> Alan<br>
> >><br>
> >><br>
> >> Hear Alan Every Week on Let's Talk Business
The UK's Premier Radio<br>
> >> Programme For Current and Future
Entrepreneurs - Now Broadcast To Over<br>
> >> 5 Million People
<a class="moz-txt-link-rfc2396E" href="http://www.letstalkbusinessonline.com/"><http://www.letstalkbusinessonline.com/></a><br>
> >><br>
> >><br>
> >> From: "<a class="moz-txt-link-abbreviated" href="mailto:tlr@gairloch.co.uk">tlr@gairloch.co.uk</a>
<a class="moz-txt-link-rfc2396E" href="mailto:tlr@gairloch.co.uk"><mailto:tlr@gairloch.co.uk></a>"<br>
> >> <<a class="moz-txt-link-abbreviated" href="mailto:tlr@gairloch.co.uk">tlr@gairloch.co.uk</a>
<a class="moz-txt-link-rfc2396E" href="mailto:tlr@gairloch.co.uk"><mailto:tlr@gairloch.co.uk></a>><br>
> >> Reply-To: "<a class="moz-txt-link-abbreviated" href="mailto:tlr@gairloch.co.uk">tlr@gairloch.co.uk</a>
<a class="moz-txt-link-rfc2396E" href="mailto:tlr@gairloch.co.uk"><mailto:tlr@gairloch.co.uk></a>"<br>
> >> <<a class="moz-txt-link-abbreviated" href="mailto:tlr@gairloch.co.uk">tlr@gairloch.co.uk</a>
<a class="moz-txt-link-rfc2396E" href="mailto:tlr@gairloch.co.uk"><mailto:tlr@gairloch.co.uk></a>><br>
> >> Date: Sunday, 8 March 2015 00:45<br>
> >> To: "<a class="moz-txt-link-abbreviated" href="mailto:transplanfm@hotmail.com">transplanfm@hotmail.com</a>
<a class="moz-txt-link-rfc2396E" href="mailto:transplanfm@hotmail.com"><mailto:transplanfm@hotmail.com></a>"<br>
> >> <<a class="moz-txt-link-abbreviated" href="mailto:transplanfm@hotmail.com">transplanfm@hotmail.com</a>
<a class="moz-txt-link-rfc2396E" href="mailto:transplanfm@hotmail.com"><mailto:transplanfm@hotmail.com></a>>, Associated<br>
> >> Consultants <<a class="moz-txt-link-abbreviated" href="mailto:info@a-bc.co.uk">info@a-bc.co.uk</a>
<a class="moz-txt-link-rfc2396E" href="mailto:info@a-bc.co.uk"><mailto:info@a-bc.co.uk></a>><br>
> >> Cc: "<a class="moz-txt-link-abbreviated" href="mailto:cma-l@mailman.commedia.org.uk">cma-l@mailman.commedia.org.uk</a><br>
> >>
<a class="moz-txt-link-rfc2396E" href="mailto:cma-l@mailman.commedia.org.uk"><mailto:cma-l@mailman.commedia.org.uk></a>"
<<a class="moz-txt-link-abbreviated" href="mailto:cma-l@mailman.commedia.org.uk">cma-l@mailman.commedia.org.uk</a><br>
> >>
<a class="moz-txt-link-rfc2396E" href="mailto:cma-l@mailman.commedia.org.uk"><mailto:cma-l@mailman.commedia.org.uk></a>><br>
> >> Subject: Re: [cma-l] Ofcom announces trials
to help small stations<br>
> >> join digitalradio - 100w limit<br>
> >><br>
> >> I simplistically presumed they settled on
the 100W suggested limit on<br>
> >> the basis that at the Band III frequencies
of DAB it would give<br>
> >> roughly the same coverage area (at
58dBuV/99%) as 25W on Band II (at<br>
> >> 54dBuV/90%).<br>
> >> NB the average *local* DAB multiplex power
is 1.3kW, not 2kW, but of<br>
> >> course they tend to be from sites with much
higher antennas than<br>
> >> economically available to community
stations, so the chances are the<br>
> >> 100W represents an even tinier coverage area
in comparison to current<br>
> >> local multiplexes than might appear at first
sight from a simple<br>
> >> comparison of powers. But I can see it is
much easier for Ofcom to<br>
> >> control the allowed power than to get into
arguments over exact<br>
> >> percentages of area covered. Maybe 500W
would have been more realistic<br>
> >> if they wanted to take that simplistic
approach, with a lower limit<br>
> >> applied in the few cases where 500W coud
cause difficulties.<br>
> >> (I guess there is also the question that
Ofcom is paying for the<br>
> >> transmitters in the trial, and a band III
amplifier running at , say,<br>
> >> 250W is a lot more expensive than a 50W one,
especially if one uses<br>
> >> the technique of greatly underrunning a much
higher power design to<br>
> >> help achieve the necessary linearity.).<br>
> >> Seems to me that block 5A, (currently
unused, but allocated for local<br>
> >> DAB) could be used as a UK-wide frequency
block for terrain limited<br>
> >> single station services up to 500W to deal
with all the areas where<br>
> >> there is a low density of local stations (ie
only one within the<br>
> >> interference range of a 500W TX) and it
could be done tomorrow,<br>
> >> without any fancy trials or risk of
interference, clearing out one<br>
> >> whole tier of demand without any fuss,
leaving trials and more<br>
> >> complicated sharing and co-channel planning
issues to be threshed out<br>
> >> over time in the other seven frequency
blocks allocated to local<br>
> >> ensembles in areas of more dense demand.
It's also much lower in<br>
> >> frequency than the other blocks, which
reduces the demands on the<br>
> >> low-cost software defined transmitter.<br>
> >> Alex<br>
> >><br>
> >> On 25 February 2015 at 13:04 Associated
Broadcast Consultants<br>
> >> <<a class="moz-txt-link-abbreviated" href="mailto:info@a-bc.co.uk">info@a-bc.co.uk</a>
<a class="moz-txt-link-rfc2396E" href="mailto:info@a-bc.co.uk"><mailto:info@a-bc.co.uk></a>> wrote:<br>
> >><br>
> >> We challenged the 100w limit in the
consultation - suggesting that<br>
> >> the "no greater than 40% of the local
commercial Mux area" was an<br>
> >> adequate limit. 100w is roughly 5% of the
average existing DAB<br>
> >> transmitter power, so presuming community
stations don't deploy<br>
> >> their DAB transmitters using tethered
balloons or satellites etc<br>
> >> they unlikely ever to get near 40% unless
they deploy multiple<br>
> >> numbers of transmitters (thus undermining
the low-cost aim).<br>
> >> The standard consultation deflection
response was invoked (ie:<br>
> >> address a different question) - stating that
"it is not<br>
> >> necessarily the case that allowing a higher
power will in all<br>
> >> cases reduce the number of transmitters
needed". We never said it<br>
> >> would in all cases, but were suggesting that
by removing the 100w<br>
> >> cap you retain some flexibility when it
/would/ make a difference<br>
> >> in some cases! Unfortunately though,
consultations are single shot<br>
> >> - no possibility to clarify the point or
challenge the response.<br>
> >> I think we can all imagine the real
(unstated) reason why they are<br>
> >> limiting it to 100 watts ;-)<br>
> >> Don't get me wrong - 100w at 200MHz can
still provide useful<br>
> >> coverage if planned correctly (other DAB
coverage planning<br>
> >> services are available!), but in some cases
more may be required.<br>
> >> Otherwise we risk repeating the same problem
that analogue CR has<br>
> >> - the paltry standard 25w power is often
inadequate and quite<br>
> >> literally blasted off the dial by much
stronger commercial and BBC<br>
> >> signals. And this problem is even worse with
DAB (for technical<br>
> >> reasons that I will not go into here).<br>
> >> Glyn<br>
> >> --<br>
> >> Glyn Roylance - Principal Consultant<br>
> >> Associated Broadcast Consultants
<a class="moz-txt-link-rfc2396E" href="http://www.a-bc.co.uk/"><http://www.a-bc.co.uk/></a><br>
> >>
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