The 450 band
The first real Nordic decision was about frequencies. To begin with, the Swedish participants had advocated the 250 MHz band, but this was used by NATO and therefore impossible for NATO members Denmark and Norway. The Danes and Norwegians suggested the 450 MHz band instead, which they had used for their earlier manual mobile systems. This, however, was reserved for the armed forces in Sweden for use both during mobilization and hostilities. They had invested heavily in military equipment using this frequency band.
Haug recalls: “After lengthy negotiations, we came to a compromise. The defense authorities accepted our use of the frequency band in peacetime. If mobilization was required, the defense forces would be able to use half the band.”
Another early discussion point was whether the mobile terminals should be portable (not mounted permanently in vehicles). In Denmark, mobile stations were forbidden because of the risk that “in practice, they could become stationary” and thereby interfere with television and radio reception. In Norway, on the other hand, portable stations were seen to play an important role for mountain rescue services. Norway also allowed the installation of fixed stations in areas that cable networks could not reach.
One fundamental issue was whether there should be a large number of short-range base stations or a small number of long-range ones. The former would offer advantages in urban areas, which had many subscribers. But subscribers in such a scenario could be expected to move frequently from one base-station area to another, and this would make major demands on the automatic handover system.
The NMT group also discussed in 1971 whether it was realistic to attempt to create a European mobile telephone system. It concluded that there would be major problems in reaching agreement on radio frequencies, signal systems and other matters, and that work towards a European system would have to take “a very long-term view.”
Agreement on the 450 MHz band made it possible to launch mobile telephony across the Nordic borders with the existing MTD system. This came into use in Denmark in 1974 and Norway in 1976, and meant in principle that an MTD phone could be used as subscribers traveled around in Sweden, Norway and Denmark, and – if there was coverage – could theoretically allow them to call anywhere in the world. In this way MTD also became a test bench for international commercial cooperation.
There were examples of base stations in the territory of other countries – for example, Germany had placed base stations for its automatic B-Netz system in neighboring Austria. But apart from this, MTD was probably the world’s first mobile system designed for cross-border use.
Author: Svenolof Karlsson & Anders Lugn
Frequency spectrum as planned for use in Sweden in 1978; the frequency chart was reworked by Televerket’s frequency expert, Krister Björnsjö.