[opendtv] Re: IBA Technical Review available online

  • From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
  • To: "opendtv@xxxxxxxxxxxxx" <opendtv@xxxxxxxxxxxxx>
  • Date: Wed, 4 Dec 2013 01:25:58 +0000

Donald Koeleman wrote:

> Currently broadcasters are being forced onto DAB+.

This is what I expected from the start. As usual, these choices of broadcast 
system are political. Any pretense at technical reasons always sounds lame.

I am aware of the codec update in DAB+, which brings it in line with DRM and HD 
Radio, however the frequency bands used for DAB+ continue to be bands in much 
higher demand than the analog AM and FM radio bands.

DAB+ is designed for Band III, Band IV, and the L Band.

Band III is the TV VHF band, available in the UK but not elsewhere. Other 
European countries do use VHF for TV.

Band IV is the TV UHF band. So that's 470-614 MHz in the UK, expanded in the 
upper regions for non-TV use.

The L Band is 1 to 2.6 GHz, much better used for cellular systems or satellite, 
actually. Although DAB+ does include a satellite mode, so I suppose that's what 
the L-Band is being retained for. But that's not why it was first introduced.

So none of these options includes the lower frequencies, which work very well 
for one-way terrestrial broadcast digital radio, where channel widths can be 
much narrower than those used for TV or for wireless broadband, and where you 
want good propagation qualities.

On the other hand, both HD Radio and DRM are specified for the traditional 
radio AM and FM bands. DRM also goes to shortwave.

> The government being forced into the release of frequencies and the
> public broadcasters having to reduce its coverage.

Reduction of coverage is probably due in large part to the much higher 
frequencies being used, compared with FM (or AM). L Band would be particularly 
bad for this. Canada found this out and disbanded DAB entirely (CBC quit DAB in 
2010). They're testing HD Radio instead, which quite honestly, is a darned good 
idea. Assuming broadcast radio needs to continue.

Here is the good ole USA, when radio stations transmit HD Radio (which in this 
market they virtually all do), they still have to use hybrid mode. So their 
first digital channel is a simulcast of the analog channel, and then they 
typically offer one or two other channels in addition, all on the same 
frequency channel as the analog. But "cheating," by making low power use of the 
guard bands. In full digital mode, the power can be increased by at least 10X, 
and more than 10X in the AM band, compared to the very low power they are 
restricted to in hybrid mode.

Come on Europe. Do the right thing. DRM or HD Radio.

Bert

 
 
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