GCHQ Letter Points To Powerline Interference


A letter from GCHQ suggests power line networking interferes with spooks, or does it just affect radio amateurs?

A broadband technology that is being used in British homes is hampering the ability of the UK’s top secret listening station, GCHQ, to do its job.

The information came to light in a letter written by GCHQ’s spectrum manager back in March, but according to various media reports the letter has been officially renounced by the organisation because of inaccuracies and is not apparently an official document.

However the letter (PDF file) is available on the site of pressure group Ban PLT and features GCHQ logos and letterheads.

Power Line Interference

“GCHQ wishes to express its concern over the manufacture, importation and sales of equipment used in support of the above technologies (i.e. power line technology and associated home networking devices,” reads the letter.

It then goes on to say that interference from power line networking “is likely to cause a detrimental affect to part of the core business of this Department”.

For those that don’t know, power line networking is typically used in homes where owners utilise the mains wiring in their building as an alternative to a Wi-Fi signal. This allows computers or devices to connect to the web in room or areas of the house that struggle to receive a viable WiFi signal. In January it was announced that 1,000 Liverpool homes would get broadband over power lines.

Comtrend is the leading manufacturer here and has apparently supplied the technology to more than 1.5 million UK households via BT.

“We are already measuring an increase in the HF noise floor in the vicinity of our HF receiving stations, with wide variations between day time and night time levels. The propagation of noise in this band also varies according to seasonal changes and other natural phenomena,” the letter states.

“Other interference issues have been raised by the MoD, the BBC, RSGB, and other players in the telecommunications industry.”

Ofcom Statement

“The Wireless Telegraph Act also gives the provision for Ofcom to act against specific instances of interference from this technology when in use. We urge them to adopt such powers,” the letter concludes.

eWEEK Europe UK approached Ofcom to get its take on whether there really is inference from power line networking.

“There are about 1.8 million pairs of PLT products in the UK. Since 2008 we have received 272 complaints relating to these devices. These have come from one user group – amateur radio users,” said the Ofcom spokesperson.

“Complaints of interference have shown a significant decline of about two thirds over the past twelve months (compared with the previous 12 months i.e.147/53). This is against an increased take-up of the technology.”

Indeed, it seems that the only group that has actually complained about power line networking is ham radio enthusiasts – and a quick search on Google revealed that the letter’s author  is also the chair of an amateur radio group.

News sites covering this story have been asked by GCHQ, under the DA Notice system not to name the GCHQ employee in question or link to the site where the letter is hosted

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Author: Tom Jowitt
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