Abstract :
The HF bands still have valuable properties in terms of their ability to provide long-distance communications without intermediaries. As a result, new systems continue to be developed for them. An example is the new digital broadcasting system under development by the Digital Radio Mondiale (DRM) consortium, which promises to re-invigorate broadcasting in the frequency bands below 30 MHz. But both existing and new users of these bands face the challenge of potential new sources of interference, namely various systems such as power line telecommunications/transmission (PLT) and xDSL which use existing mains and telephone wiring respectively for communications purposes. Calculations for a PLT system, whose results are summarised, show that very many radio users stand to suffer serious disruption of their services if this kind of (wired) communications system were allowed to be widely deployed. The problem clearly has an international dimension-interference can be caused at very considerable distance from the source-and any `local´ permission to `use´ a part of the HF band for wired systems would deny it to others elsewhere for legitimate radio. It would also hamper subsequent re-planning of the HF band for radio users and new radio systems
