The British DX Club

Shortwave interference from Power Line Modems / Ethernet Adaptors and other electrical devices

One of the most serious threats to our hobby of shortwave DXing and listening comes in the form of a little device designed to distibute broadband and television signals through domestic mains wiring. Severe interference across the shortwave band from 3-30 MHz is the effect of these units known as "Power Line Modems" or "Power Line Adaptors".

One model in particular, which was initially supplied to BT Vision customers in the UK, caused a great deal of concern - Comtrend model DH-10PF. It has since been recalled by BT but there may still be units in use. Devices from other manufacturers are also reported to cause similar interference. The interference, in the form of a high pitched digital noise, has been noted from such devices 24 hours a day over a wide area, often exceeding 100m.

Update 2017: We are receiving reports of severe interference on the HF bands from Sky Q TV installations using the power line communications system PLT. Although Sky Q has notches to reduce interference on the amateur radio bands the shortwave broadcast bands are not notched and broadcast signals can be completely obliterated by severe PLT interference from Sky Q installations. It can effectively render the SW bands unusable.

Severe short wave interference can also be caused by other electronic apparatus such as plasma television receivers, switch mode power supplies, LED lighting systems, touch tone lights, security alarms, faulty street lights, etc. The web sites below will help you to identify the type of interference you are suffering from.

Further Information

For more information about interference from Power Line Adaptors and other sources of electrical interference see the UK QRM web site.

A web site set up specifically to campaign against Power Line Adaptors is at Ban PLT.

Helpful information and advise on solving general short wave interference problems is also available on the RSGB web pageI am experiencing interference

Examples of PLT interference

Demonstrations of interference from Power Line Adaptors can be found on Youtube. Simply search for "PLT interference".

Reporting the interference

Since July 2010 the BBC has been handling complaints about domestic radio and TV reception in the UK, although any complaints about short wave interference should continue to be reported to Ofcom. The BBC has set up a web site Radio & TV Investigation Service to help viewers and listeners with domestic radio and TV reception problems.

Complaints about interference from Power Line Adaptors from both licensed amateurs and short wave listeners can be made to Ofcom using the form which is labelled "Report interference or abuse to an amateur radio system" (Interference from Power Line Adaptors is regarded as spectrum abuse). If you do not have an amateur call sign you should put "N/A" in the "Your licence number" and "Your call sign" boxes. You can also phone Ofcom's advisory team on 0300 123 3333.

Don't worry about any fees as this would not apply if the source of the interference is outside your property. After you report a complaint, Ofcom should send an engineer to investigate the source of the interference. This will be treated confidentially by Ofcom and if it turns out to be BT Vision adaptor in a neighbouring property, they can ask BT to solve the problem. In most cases BT are able to replace the PLT adaptors with a hard wired or wi-fi link to remove the interference. By mid 2011 Ofcom had dealt with around 280 cases of interference from PLT devices reported by shortwave listeners, many of which had been satisfactorily resolved. We hope that this will also be the case where Sky Q installations are found to be radiating unacceptable shortwave interference.

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Updated: 7 Sep 2017