Re: [Swprograms] Interesting DRM wrinkle: Synchronized single-frequency transmitters (Deutsche Welle)

[Mike Barraclough <softbulletin1@xxxxxxxxx>]

> Hmmm...I thought that DRM was supposed to reduce
> transmitter power
> requirements, not increase those requirements.

Just because it is digital does not mean it is immune
to propagation and interference. The BBC WS DRM
service to Europe is a network including AM 648 which
has an AMSS encoder fitted to it allowing a signal to
be added to the analogue transmission, this very low
bit rate signal uses a low level of phase modulation
to provide station name and alternative frequency
information thus enabling the receiver to switch to it
if it cannot find a suitable DRM frequency.

The other requirement DRM needs is some form of
monitoring system so that the bandwidth and robustness
of the system can be altered at times of unfavourable
propagation, albeit at the expense of audio quality.

Mike




		
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