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<div class="moz-cite-prefix">I'm not so sure about that analysis,
after all, the report implied that it was the SDR that was
under-run at 5mW presumably because the output daughterboard was
intended for AM/FM modulation? Also, it was common IBA practice
to run a several kilowatt bottle at a hundred watts or so, the
excess input power being necessary to ensure class A linear
operation. The point being that the rf amp has to be linear, and
it isn't, you can't just turn it down a bit.<br>
<br>
Tony Bailey<br>
<br>
<br>
On 09/03/15 22:41, <a class="moz-txt-link-abbreviated" href="mailto:tlr@gairloch.co.uk">tlr@gairloch.co.uk</a> wrote:<br>
</div>
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cite="mid:1897030229.182675.1425940898814.JavaMail.open-xchange@oxbaltgw15.schlund.de"
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<div> Pete: We know what software and modulator they will probbaly
be using, but one of the key features of Ofcom's proposals for
low-cost DAB broadcasting is avoiding the use of the
conventional large and expensive DAB mask filters (typically
6-cavity high power devices) on th efinal output. </div>
<div> </div>
<div> This can be achieved by a combination of tactics, including
a very under-run driver stage (eg 100mW stage running at only
5mW) and relatively underrun RF amplifiers (eg maybe using an
amplifier potentially capable of say 250-500W continuous carrier
power to produce a DAB signal of less than 100W), so that there
are fewer spectral regrowth components to be filtered. Plus with
the whole kit running at relatively low ERP anyway, the
filtering is not as critical as it would be for a high-power
transmitter because the absolute level of spurious products is
low relative to neighbouring high-power signals and aeronautical
limits. </div>
<div> </div>
<div> Alex </div>
<div> <br>
> On 09 March 2015 at 20:18 Pete
<a class="moz-txt-link-rfc2396E" href="mailto:peter@engineeringradio.co.uk"><peter@engineeringradio.co.uk></a> wrote: <br>
> <br>
> <br>
> It's obvious what type of exciter they will be using if you
have been following them. It's obvious it will be SDR based. The
amps may be a different matter. I don't think it is clear what
they would be using. They would probably use filtering to the
spec set out for DAB. </div>
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