Monday 23 January 2017

Start of FM Switch-off in Norway Reveals DAB Vulnerability

Norwegian government close to a national broadcasting failure.
In the balance before February 8: Trøndelag and Geneva.

After starting the switch-off of FM transmitters for nationwide radio in Nordland county January 11 many listeners had sparse or no DAB reception at all. Quite different from what the public service broadcaster NRK has promised. There are strong indications that DAB will not be complete and sufficient replacement for FM. Now the government has to decide upon a switch-off postponement for the rest of the country. But the official picture of the switch-off is still bright with pomp and circumstance.

After a week, half of the respondents in a survey said that they have left NRK in Vesterålen area when FM transmitters were turned off. In Narvik, with about 20,000 residents reported that more than 50% of the listeners could not receive DAB + and about 25% had unstable coverage. It is estimated that 75-80% of Narvik's population no longer had access to NRK.

The cause of the coverage problems with DAB cannot primarily be blamed on flawed technical preparedness of NRK and broadcast provider Norkring. The DAB system has built-in flaws in stability and range. In this respect, the FM system retains its superiority.

Veteran radio technician Lars Mossberg in Stockholm says that to cover an entire area with DAB using a mux (multiplex) with many simultaneous radio channels takes up a broader spectrum than a single FM channel. This means automatically a problem to cover a specific geographical area. This, together with a higher transmission rate and error protection that is not optimized require both more powerful ERP output power for the antennas, more transmitters which are almost as closely spaced as mobile network transmitters. Only then will you benefit from more simultaneous transmitters transmitting on the same frequency (SFN).

DAB is also a treacherous system because reception is very close to the authorized threshold value. This means that the environment and the weather can sometimes play in as the reception of DAB mux severely limited. When such weather occurs, it gives problems in a mux with numerous DAB channels. Therefore the system is uncertain at times. Since the transmitters operate at maximum output power there are no reserves left and then reception holes easily rather occur.

Mobile network transmitters are often heavily throttled to accommodate more concurrent users. Coverage holes can be filled with problems, and this is controlled by the operators at the expense of the number of users that can use the network simultaneously, says Mossberg to Public Access.

Why then has not the these problems been observed in other countries where there are regular DAB broadcasts? According to a German expert, it is simply that in Germany and other countries where DAB or DAB + still ithe basic platform for terrestrial radio still is FM. Everyone has access to FM.

If there is such reception problems with DAB, which are now reported from Nordland, changing radio listeners simply because usually FM receivers, particularly for radio, has both DAB / DAB + and FM. This can partly be done automatically when the DAB falling out. But in Norway, the radio listener now does not have the any option for receiving terrestrial radio. Problems also becomes clear in Nordland and other sparsely populated areas, unlike for example in some European metropolitan cities where there are always several platform options for radio listeners.

This week the Norwegian Minister of Culture Helleland is due to present the report on the work of the switch-over to the Parliament which in December  demanded that the Government should report on this regularly. The Conservative media policy spokesman in the Parliament Svein Harberg, has been clear that in the worst case the government must postpone the FM switch-off, if not everything works out as planned.

However, it is not likely that such a decision is taken before the next scheduled switch-off in Trøndelag, Møre and Romsdal fylke on February 8 because this event is coordinated by the EBU's "Digital Radio Summit" in Geneva the same day. A deferred switch-off announced before the conference would be an embarrassing loss of prestige for the government, NRK and the DAB lobby.

Also read
Norwegian Broadcast Engineer Discusses Impending FM Shutdowns
National Radio Network Switch-over from FM to DAB+ in Norway
Local Radio Demanding FM Frequencies Left By National Channels Going DAB