BBC R&D

Abstract

A visit to Crieff in June 2004 is described, in which measurements were made to assess the emisssions of a Power-Line Telecommunications (PLT) system and its propensity to cause interference to HF radio reception. The PLT system was developed by the Spanish company DS2 whose representative unfortunately prevented measurements being made in a way that was either comparable to tests made on other systems in 2002 or of obvious relevance to normal radio reception. All measurements were outdoors whereas normal radio reception takes place inside listeners' homes. This was unfortunate, especially as DS2 makes claims of significant advances in reducing interference which it would have been good to confirm.

Nevertheless it was possible to demonstrate that significant interference was still caused to reception at the outdoor locations and it would be reasonable to infer that this would apply with at least equal force to reception indoors.

The DS2 system had some capacity for inserting notches in the used spectrum which was explored in the tests. Nothing was seen to mitigate interference substantially in the bands where it was applied.

Some audio recordings demonstrating the effects of interference and the benefits of notching have been made available for download and are described in the document.

The measurements, their limitations, and what can nevertheless be inferred from them are discussed at some length. There remains a clear need to perform an unencumbered assessment of this PLT system (and any future ones also claiming improvements in interference mitigation) so that the threat from PLT to reception of HF broadcasting can be properly assessed.