Salut Phil,
[...]
 JK>> DAB is intended for terrestrial broadcast ("over the air"). It is not
 JK>> related to any TV format.
 PR> OK, so this is sent over a carrier on conventional FM?  Sounds like it'd
 PR> be simple enough to implement.
No, it's not that simple.
DAB uses COFDM and a different frequency spectrum:
.....cut.....
In the COFDM (Coded Orthogonal Frequency Division Multiplex) the signal to be 
transmitted is distributed to a great number of narrow-band transmission 
channels (sub-bands). With such an approach only one information segment is 
lost at maximum in the event of interference on a frequency range - which is 
different from FM broadcasting where a programme were interfered entirely.
In order to keep the interference at a minimum level the COFDM technique 
provides the useful signal with extensive error protection (redundancy). 
Moreover, the individual COFDM symbols are emitted with a guard interval so 
that reflected waves which arrive within the interval may be identified and 
used in perfect condition. The information is initially collected in a buffer 
where a composite signal is generated - by contrast to analog transmission, 
the multipath reception in COFDM even enhances the quality in transmission.
The application of a frequency block with a width of 1.5 MHz has been adopted 
for the DAB system; depending on the transmission mode 192 to 1536 sub-bands 
are modulated on this block, which generates an ensemble. This ensemble is 
then transmitted at a gross bit rate of 2,304 bits per second, which 
corresponds to a net bit rate of roughly 1.2 to 1.5 megabits per second, in 
dependence on the protective features.
Up to 7 MUSICAM-encoded stereo programs and additional data services can be 
transmitted in this bandwidth, or a correspondingly higher number of mono 
programmes or programmes with lower demands on the audio quality. The 
allocation of data rates to individual providers and services and the 
administration of these data rates is referred to as bit rate management.
System details:
Radio frequency properties : Mode I  : Mode II : Mode III : Mode IV :
Bandwith                   :             1.536 MHz                  :
Number of carriers         :1536     : 384     : 192      : 768     :
Total modulation interval  :1.246 ms :0.312 ms :0.156 ms  :0.623 ms :
Guard interval             :0.246 ms :0.062 ms :0.031 ms  :0.123 ms :
Modulation                 : differential 4-phase modulation (QPSK) :
Service technology
Frequency range for speeds :<300 MHz :<1.2GHz  :<3GHz     :<600 MHz :
< 130 km/h                 :         :         :          :         :
Coverage area for single   :           terrestrial even             :
transmitters               :                                        :
supranational service by   :   ---   :satellite:satellite :   ---   :
Distance between trans-    :up to ap.:up to ap.:up to app.:up to ap.:
mitters in terrestrial SFN :60 km    :20 km    :10 km     :30 km    :
Multiplex properties
Gross transmission rate     2.304 MBit/s
Net transmission rate       ca. 1.2 MBit/s
(degree 3)
Free configurability        up to 64 audio programmes and data services, in
                            typical cases 5 to 8 audio programmes and several
                            data services
Reconfigurability           dynamic during programme operation
Typically unbalanced        6 stereo programmes with 192 kBit/s each,
configurations              including PAD plus 24 kBit/s for data services
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Hope this is still readable. MUSICAM is also known as MPEG Layer II.
 JK>> I have no idea about the situation in the USA, but as far as I know,
 JK>> the NAB (National Association of Broadcasters) refuses the
 JK>> introduction of DAB in the USA. Apparently because of internal
 JK>> political reasons, they have admitted the technical superiority of
 JK>> DAB.
 PR> I'd suspect ASCAP has something to do with it.  Any time audio is
 PR> distributed in a digital format, ASCAP worries about piracy.
Same scenario as with the DVD, I suppose.
bye ....
         Joe
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