The British DX Club

Shortwave interference from Power Line Modems / Adaptors

There is a new and deadly threat to our hobby of Shortwave DXing and Listening and it comes in the form of a little device designed to distibute broadband and television signals through the 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 being supplied to BT Vision customers in the UK seems to be causing the most concern. The models in question are usually made by Comtrend - model DH-10PF. 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.

UK QRM videos

See a demonstration of the interference on Youtube

Demonstration of BT Vision interference

Second video with update

Third video - Know Your Enemy Demonstration of interference from the Comtrend adaptor and how to track down interference.

Reporting the interference

Since July 2010 the BBC has been handling complaints about domestic radio and TV reception, 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 should continue to be made to Ofcom using Ofcom's 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 will be able to replace the Comtrend 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 April 2012 It is now reported by UKQRM that Ofcom is no longer accepting complaints directly except 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.

UKQRM news group

If you are suffering from this interference from a neighbour or are concerned about the issue, we also recommend you join UKQRM. The group is campaigning to get these devices withdrawn and also offers advice on how you can get Ofcom and BT to resolve a specific interference complaint. UKQRM Yahoo group

Further Information

For more information about interference from Power Line Adaptors see the UK QRM web site

Helpful information and advise on solving general short wave interference problems is also available on the RSBB web siteRSGB interference page