Effect of HF broadcast interference on powerline telecommunications above 1 MHz

In response to the liberalisation of telecommunications service provision in the U.K., NOR.WEB has demonstrated the use of the LV (240/415 V in the U.K.) mains network for the provision of a wide range of digital powerline telecommunication services to customers. NOR.WEB has shown that communication is possible in the HF region of the spectrum, above 1 MHz. One of the many problems associated with the HF frequency range is ingress of HF broadcast carriers, which can cause significant interference with the powerline communication signal. This paper describes the results of measurements made on the mains network to characterise the interference encountered at these frequencies. HF ingress was indeed one of the most significant sources of interference discovered. Hence hardware and software were developed to identify these signals on the network, and to collect statistics on their distribution. The paper also discusses the distribution of their amplitude, and also their distribution with frequency and time-of-day. The results are used to give limits (to a given statistical confidence level) on the interference encountered by a powerline telecommunication system, as a function of its bandwidth.