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 November 2015: The new Sky Q TV system will reportedly use the power line communications system PLT which has the potential to render the HF radio spectrum 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, but any complaints about short wave interference should continue to be reported to Ofcom. You can report interference to domestic BBC services filling in the online form at this link TV or Radio Interference or 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 abuse on 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 will 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.

Update It is now reported by UKQRM that Ofcom is only accepting complaints from licensed radio amateurs and that complaints from broadcast listeners should, in the first instance, be made throught the BBC's Radio and Television Interference Service (link above) which should then refer such cases to Ofcom for action. However complainants have been receiving the following message from RTIS:
"Ofcom will not accept a referral from RTIS or undertake an investigation where:
1) Interference only affects equipment using indoor aerials.
2) Interference only affects LW/MW (AM) services.
3) Interference only affects non-domestic services; eg, short wave services.
4) Interference only affects non-broadcast service; eg, alarms, portable phones, Wi-Fi systems, Amateur Radio users."

We recommend that you initially report cases of short wave interference to Ofcom but if your complaint is not accepted by Ofcom then you should report it to the BBC and request that the BBC refer it to Ofcom on your behalf.

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Updated: 20 Nov 2015