<html>
<head>
<meta content="text/html; charset=ISO-8859-1"
http-equiv="Content-Type">
</head>
<body bgcolor="#FFFFFF" text="#000000">
<div class="moz-cite-prefix">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.<br>
<br>
Tony Bailey<br>
<br>
On 08/03/15 14:01, Ian Hickling wrote:<br>
</div>
<blockquote cite="mid:DUB125-W706449DF6E4C1DC8CC5130AD1A0@phx.gbl"
type="cite">
<style><!--
.hmmessage P
{
margin:0px;
padding:0px
}
body.hmmessage
{
font-size: 12pt;
font-family:Calibri
}
--></style>
<div dir="ltr">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.
<div>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.</div>
<div>Topography, geology, refraction, refraction, foliation,
antenna efficiency and launch conditions have far too large an
influence.<br>
<div>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.</div>
<div>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.</div>
<div>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.</div>
<div>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.<br>
Beware - there is a distinct difference between a Power
Decibel in transmission and a Voltage Decibel in reception!</div>
<div><br>
</div>
<div>Let's not invoke DAB+ and DRM - Ofcom specifically rules
them out in 2.30 and 2.32</div>
<div><br>
</div>
<div>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.</div>
<div><br>
</div>
<div>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.</div>
<div><br>
</div>
<div>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.</div>
<div><br>
</div>
<div>Let's not get distracted - the encoding is
software-defined - the actual RF transmitter is not!</div>
<div><br>
</div>
<div>Ian<br>
<br>
<div>
<hr id="stopSpelling">Date: Sun, 8 Mar 2015 11:13:25 +0000<br>
Subject: Re: [cma-l] Ofcom announces trials to help small
stations 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>
<div>
<div>I can’t help thinking that someone at Ofcom ran the
simulations and came up with 100W = 5km radius. </div>
<div><br>
</div>
<div>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. </div>
<div><br>
</div>
<div>Kind Regards</div>
<div>
<div style="font-size:14px;">
<p class="ecxEmail"><span style="font-size:15px;">Alan<br>
<br>
<span style="color:blue;"><br>
<a moz-do-not-send="true"
href="http://www.letstalkbusinessonline.com/"
target="_blank">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 </a><br>
</span><br>
</span></p>
</div>
</div>
</div>
<div><br>
</div>
<span id="ecxOLK_SRC_BODY_SECTION">
<div
style="font-family:Calibri;font-size:11pt;text-align:left;color:black;BORDER-BOTTOM:medium
none;BORDER-LEFT:medium
none;PADDING-BOTTOM:0in;PADDING-LEFT:0in;PADDING-RIGHT:0in;BORDER-TOP:#b5c4df
1pt solid;BORDER-RIGHT:medium none;PADDING-TOP:3pt;"><span
style="font-weight:bold;">From: </span> "<a
moz-do-not-send="true"
href="mailto:tlr@gairloch.co.uk">tlr@gairloch.co.uk</a>"
<<a moz-do-not-send="true"
href="mailto:tlr@gairloch.co.uk">tlr@gairloch.co.uk</a>><br>
<span style="font-weight:bold;">Reply-To: </span> "<a
moz-do-not-send="true"
href="mailto:tlr@gairloch.co.uk">tlr@gairloch.co.uk</a>"
<<a moz-do-not-send="true"
href="mailto:tlr@gairloch.co.uk">tlr@gairloch.co.uk</a>><br>
<span style="font-weight:bold;">Date: </span> Sunday,
8 March 2015 00:45<br>
<span style="font-weight:bold;">To: </span> "<a
moz-do-not-send="true"
href="mailto:transplanfm@hotmail.com">transplanfm@hotmail.com</a>"
<<a moz-do-not-send="true"
href="mailto:transplanfm@hotmail.com">transplanfm@hotmail.com</a>>,
Associated Consultants <<a moz-do-not-send="true"
href="mailto:info@a-bc.co.uk">info@a-bc.co.uk</a>><br>
<span style="font-weight:bold;">Cc: </span> "<a
moz-do-not-send="true"
href="mailto:cma-l@mailman.commedia.org.uk">cma-l@mailman.commedia.org.uk</a>"
<<a moz-do-not-send="true"
href="mailto:cma-l@mailman.commedia.org.uk">cma-l@mailman.commedia.org.uk</a>><br>
<span style="font-weight:bold;">Subject: </span> Re:
[cma-l] Ofcom announces trials to help small stations
join digitalradio - 100w limit<br>
</div>
<div><br>
</div>
<div>
<div style="">
<div> 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%). </div>
<div> </div>
<div> NB the average <strong>local</strong> 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. </div>
<div> </div>
<div> (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.). </div>
<div> </div>
<div> 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. </div>
<div> </div>
<div> Alex </div>
<div> </div>
<div> </div>
<div> </div>
<blockquote
style="padding-left:10px;border-left:solid 1px
blue;"> On 25 February 2015 at 13:04 Associated
Broadcast Consultants <<a
moz-do-not-send="true"
href="mailto:info@a-bc.co.uk">info@a-bc.co.uk</a>>
wrote: <br>
<br>
<div dir="ltr">
<div> 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). </div>
<div> </div>
<div> 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 <span style="text-decoration:underline;">all</span>
cases, but were suggesting that by removing
the 100w cap you retain some flexibility when
it <em>would</em> make a difference in <span
style="text-decoration:underline;">some</span>
cases! Unfortunately though, consultations are
single shot - no possibility to clarify the
point or challenge the response. </div>
<div> </div>
<div> I think we can all imagine the real
(unstated) reason why they are limiting it to
100 watts ;-) </div>
<div> </div>
<div> 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). </div>
<div> </div>
<div> Glyn </div>
<div> -- <br>
<div class="ecxgmail_signature"> Glyn Roylance
- Principal Consultant
<div> <a moz-do-not-send="true"
target="_blank"
href="http://www.a-bc.co.uk/">Associated
Broadcast Consultants</a> </div>
<div> </div>
<div> </div>
<div> </div>
<div> </div>
<div> </div>
</div>
</div>
</div>
_______________________________________________ <br>
<br>
Reply - <a moz-do-not-send="true"
href="mailto:cma-l@commedia.org.uk">cma-l@commedia.org.uk</a>
<br>
<br>
The cma-l mailing list is a members' service
provided by the Community Media Association - <a
moz-do-not-send="true"
href="http://www.commedia.org.uk"
target="_blank">http://www.commedia.org.uk</a> <br>
Twitter: <a moz-do-not-send="true"
href="http://twitter.com/community_media"
target="_blank">http://twitter.com/community_media</a>
<br>
<a moz-do-not-send="true"
href="http://www.facebook.com/CommunityMediaAssociation"
target="_blank">http://www.facebook.com/CommunityMediaAssociation</a>
<br>
Canstream Internet Radio & Video: <a
moz-do-not-send="true"
href="http://www.canstream.co.uk/"
target="_blank">http://www.canstream.co.uk/</a>
<br>
_______________________________________________ <br>
<br>
Mailing list guidelines: <a
moz-do-not-send="true"
href="http://www.commedia.org.uk/about/cma-email-lists/email-list-guidelines/"
target="_blank">http://www.commedia.org.uk/about/cma-email-lists/email-list-guidelines/</a>
<br>
_______________________________________________ <br>
<br>
To unsubscribe or manage your CMA-L mailing list
subscription please visit: <br>
<a moz-do-not-send="true"
href="http://mailman.commedia.org.uk/mailman/listinfo/cma-l"
target="_blank">http://mailman.commedia.org.uk/mailman/listinfo/cma-l</a>
</blockquote>
<div> <br>
</div>
</div>
</div>
_______________________________________________
Reply - <a moz-do-not-send="true"
href="mailto:cma-l@commedia.org.uk">cma-l@commedia.org.uk</a>
The cma-l mailing list is a members' service provided by
the Community Media Association - <a
moz-do-not-send="true"
href="http://www.commedia.org.uk" target="_blank">http://www.commedia.org.uk</a>
Twitter: <a moz-do-not-send="true"
href="http://twitter.com/community_media"
target="_blank">http://twitter.com/community_media</a>
<a moz-do-not-send="true"
href="http://www.facebook.com/CommunityMediaAssociation"
target="_blank">http://www.facebook.com/CommunityMediaAssociation</a>
Canstream Internet Radio & Video: <a
moz-do-not-send="true"
href="http://www.canstream.co.uk/" target="_blank">http://www.canstream.co.uk/</a>
_______________________________________________
Mailing list guidelines: <a moz-do-not-send="true"
href="http://www.commedia.org.uk/about/cma-email-lists/email-list-guidelines/"
target="_blank">http://www.commedia.org.uk/about/cma-email-lists/email-list-guidelines/</a>
_______________________________________________
To unsubscribe or manage your CMA-L mailing list
subscription please visit:
<a moz-do-not-send="true"
href="http://mailman.commedia.org.uk/mailman/listinfo/cma-l"
target="_blank">http://mailman.commedia.org.uk/mailman/listinfo/cma-l</a></span></div>
</div>
</div>
</div>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<br>
<pre wrap="">_______________________________________________
Reply - <a class="moz-txt-link-abbreviated" href="mailto:cma-l@commedia.org.uk">cma-l@commedia.org.uk</a>
The cma-l mailing list is a members' service provided by the Community Media Association - <a class="moz-txt-link-freetext" href="http://www.commedia.org.uk">http://www.commedia.org.uk</a>
Twitter: <a class="moz-txt-link-freetext" href="http://twitter.com/community_media">http://twitter.com/community_media</a>
<a class="moz-txt-link-freetext" href="http://www.facebook.com/CommunityMediaAssociation">http://www.facebook.com/CommunityMediaAssociation</a>
Canstream Internet Radio & Video: <a class="moz-txt-link-freetext" href="http://www.canstream.co.uk/">http://www.canstream.co.uk/</a>
_______________________________________________
Mailing list guidelines: <a class="moz-txt-link-freetext" href="http://www.commedia.org.uk/about/cma-email-lists/email-list-guidelines/">http://www.commedia.org.uk/about/cma-email-lists/email-list-guidelines/</a>
_______________________________________________
To unsubscribe or manage your CMA-L mailing list subscription please visit:
<a class="moz-txt-link-freetext" href="http://mailman.commedia.org.uk/mailman/listinfo/cma-l">http://mailman.commedia.org.uk/mailman/listinfo/cma-l</a></pre>
</blockquote>
<br>
<br>
<pre class="moz-signature" cols="72">--
Local Reports at <a class="moz-txt-link-freetext" href="http://www.ravensound.pilgrimsound.co.uk">http://www.ravensound.pilgrimsound.co.uk</a></pre>
</body>
</html>