26 MHz DRM and Band II (88-108 MHz) DRM+ Tests

DRM test transmissions are taking place in Hannover in the 11m band to determine the suitability of that band (25.67 to 26.1 MHz) for local digital broadcasting.

Like other shortwave bands, the 11m band is susceptible to interference from other broadcasting stations, or other transmissions on the same frequencies, operating in other countries. This interference varies according to the time of
day, the season of the year, the solar activity and the solar cycle.

The band could also be prone to local interference from sources such as electrical equipment, trams, overhead power lines, ADSL networks, etc.. Such interference tends at any instant to affect only some of the 43 channels available in that band.

The tests will investigate the feasability of using frequency-hopping techniques among a particular combination of those channels to avoid local interference as it occurs.

DRM receivers in the service area will be connected to the transmission control centre so that measured interference could bring about a frequency change - first manually, later automatically, at the transmitter.

The test results should help establish whether the 11m band would be suited to this type of local transmission using DRM. A number of different programme sources will be used during the tests, including those of the public-service broadcasters NDR and DeutschlandRadio, and private broadcasters such as
Truckradio and N-Joy Radio.

At present, the transmissions are centred on 26.045 MHz from the University of Hannover's Institut für Kommunikationstechnik. The Institut also plans later to test DRM+ transmissions in Band II.

From http://www.wohnort.demon.co.uk/DAB/

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