<html>
<head>
<meta content="text/html; charset=UTF-8" http-equiv="Content-Type">
</head>
<body bgcolor="#FFFFFF" text="#000000">
<div class="moz-cite-prefix">Just in case anyone hasn't had enough
of this topic, I found a useful document on the subject of Coded
Orthogonal Frequency Division Multiplexing as used for DAB - see
link below. Just to further clarify (or possibly not!) the
situation with DAB transmitters, the rated average power output
(as e.g. heating up a dummy aerial load) may be only 10% of the
peak power output. So a 100 watt (average) rated unit needs to be
capable of handling transient peaks equivalent to 900-1000 watts.
<br>
<br>
<cite class="_Rm"><a class="moz-txt-link-freetext" href="https://tech.ebu.ch/docs/techreview/trev_278-stott.pdf">https://tech.ebu.ch/docs/techreview/trev_278-stott.pdf</a><br>
<br>
</cite>Tony Bailey<br>
<cite class="_Rm"><br>
<br>
<br>
</cite><br>
On 10/03/15 16:36, Two Lochs Radio wrote:<br>
</div>
<blockquote cite="mid:08BB8E15BB91481D8AE5306C17CBAAE0@wwpc04"
type="cite">
<meta content="text/html; charset=UTF-8" http-equiv="Content-Type">
<meta name="GENERATOR" content="MSHTML 8.00.6001.23588">
<style></style>
<div><font face="Calibri" size="2">Yes, the multiplex signal
itself is one size fits all. The 'couple of stations'
does refer to economic factors rather than technical. For 10
stations each with a budget of (say) £1m sharing a 10kW
transmitter the cost equation is a bit different from from a
couple of stations each with, say, £30,000 budget buying a
100W transmitter.</font></div>
<div> </div>
<div><font face="Calibri" size="2">The old first-principles way of
measuring the average rms power of any arbitrary signal is to
feed it into a resistive load and measure how much heat it
generates. But more usually nowadays, spectrum analyzers,
which are needed anyway for commissioning a broadcast
transmitter, can easily measure the total rms power of a
signal at an instant or averaged over time. Often there is an
add-on pack for spectrum analyzers that contains extra bits
(such as a directional coupler/SWR bridge and extra software)
that calculates the various radio-related parameters such as
power, spectral occupancy, out-of-band harmonics etc. </font></div>
<div> </div>
<div><font face="Calibri" size="2">And for all I know the digital
signal processors in the SDR can also calculate the average
total power at the same time as they are doing all the amazing
on the fly maths to create the signal in the first place -
just a little bit more arithmetic for them to do on the side!</font></div>
<div><font face="Calibri" size="2">Alex</font></div>
<div> </div>
<blockquote style="BORDER-LEFT: #000000 2px solid; PADDING-LEFT:
5px; PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px"
dir="ltr">
<div style="FONT: 10pt arial">----- Original Message ----- </div>
<div style="FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color:
black"><b>From:</b> <a moz-do-not-send="true"
title="ravensound@pilgrimsound.co.uk"
href="mailto:ravensound@pilgrimsound.co.uk">Tony Bailey</a>
</div>
<div style="FONT: 10pt arial"><b>To:</b> <a
moz-do-not-send="true" title="tlr@gairloch.co.uk"
href="mailto:tlr@gairloch.co.uk">tlr@gairloch.co.uk</a> </div>
<div style="FONT: 10pt arial"><b>Sent:</b> Tuesday, March 10,
2015 3:45 PM</div>
<div style="FONT: 10pt arial"><b>Subject:</b> Re: [cma-l] DAB
trials</div>
<div><br>
</div>
<div class="moz-cite-prefix">Thanks,<br>
<br>
Arising from that (without boring the readers!) I was under
the impression that the mpex carrier was one lump, i. e.
independent of the number of programme feeds, so presumably
the "couple of stations" is an economic rather than technical
factor? How do you arrive at an average power figure for 1500
parallel carriers any of which could presumably be zero or
100%? <br>
<br>
Tony<br>
</div>
</blockquote>
</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>