In article ,
Mike wrote:

Hello,
has anyone come across any projects or info on building your own DAB radio.

This is my (limited) understanding:

How it's sent: The audio (or whatever) signal is split and sent using
Quadrature Amplitude Modulation over many narrow band carriers (each
carrier at a different frequency): Ie it's spread spectrum. Error
correction Coding is also used, etc.
To decode it: This is where I'm confused; Can I build a receiver which
will receive the whole collection of narrow band carriers, then feed it
into a computer that will do some FFT?

Yes, that's usually how it's done. The approach I've seen is to grab
the whole slice of the RF section, downconvert to a convenient IF (via
superhet or direct conversion), then feed the whole signal into
something which can use DSP to detect and demodulate the individual
carriers.

A common approach for Digital Radio Mondiale broadcasting (which has a
relatively narrow RF bandwidth) is to use a single-sideband receiver
architecture of some sort, downconverting the DRM signal from RF to a
same-width slice of audio spectrum, then feed it into a PC via the
PC's sound card, and doing the DSP work using the PC's CPU.

The commercial high-fidelity DAB systems used in the US may very well
have a bandwidth too wide to allow this simple approach to be used (I
haven't studied them in any detail) but the same basic principles
would apply. Block-convert the RF range you want to an
easily-captured IF range, do an A-to-D on it, and do the rest of the
processing digitally in a CPU or dedicated DSP chip.

Take a look at http://www.gnu.org/software/gnuradio/ for a look at
some open-source software-radio techniques.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
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