Finding QRM


Big Red Switch

A Radio Amateur's standard practise for finding interference is to turn off the mains power at the fuse board whilst listening on a battery-powered radio to see if the interference remains. If the interference is still present, it is most likely external in origin and you may need to investigate the neighbourhood. If the interference has gone away, it was something in the house, and we recommend powering up individual items until the interference comes back. Once detected, isolate that piece of equipment to double-check.

If you are suffering from PLT related interference, throwing the switch at the fuse board may not stop it from entering your property (contrary to the claims of the PLT manufacturers!). The conducted emissions injected onto the mains wiring by PLT devices travels into the homes of everyone who are also connected to the same local 11kV-415V transformer; as each home (and lamp post) shares a common neutral with the transformer. The External link Protective Multiple Earthing system employed in the UK sees the earth wires running around your house all connect back to the same common neutral; which provides a nice aerial to radiate the PLT interference! We do not recommend disconnecting the PME for your house as this will stop the safety devices in your fuse board from operating correctly.

Internal QRM

What do you do once you find it is something you use in your house? If the device has been in use for a long time, it has probably developed a fault and it should be repaired or replaced. If the device is brand new, it has been sold without meeting the EMC Directive's 'essential requirements' (and probably proper EMC compliance testing), and it should be reported to External link Trading Standards with details of where you purchased it from (receipts are always useful to keep!).

We have created a handy EMC non-compliance PDF form which you are welcome to download and use with when returning non-compliant electronics.

External QRM

Now the fun begins! The UK's national regulator, Ofcom, do not want to talk to you! They have reserved the right under their statutory duties to prosecute pirate radio stations, DJs/television presenters who swear on-air, and to make money by selling the radio spectrum to the highest bidder. If you wish to report a radio interference issue, Ofcom now want you to talk to the BBC. The BBC have no statutory powers to investigate interference complaints and can only advise on methods to ensure your aerial is working correctly. As most interference issues are non-EMC-compliant electronics, the complaint and investigation should be handled by Ofcom. If the BBC decide it is an EMC issue, they will pass you back to Ofcom; and Ofcom will pass you back to the BBC!

It gets worse! If you wish to listen to international shortwave broadcasts from other countries, Ofcom will refuse to deal with your complaint. In their eyes, you have no rights to receive broadcasts which originate outside of the United Kingdom. Article 19 of the United Nation's Universal Declaration of Human Rights states:

Everyone has the right to freedom of opinion and expression; this right includes freedom to hold opinions without interference and to seek, receive and impart information and ideas through any media and regardless of frontiers.

Is the inability to receive broadcast stations, whether internal or external to the UK, a breach of your human rights?

If you wish to report the interference to Ofcom, you can use use this link:

External link

or telephone: 0300 123 3333

Ignore the part about being a Radio Amateur and enter "n/a" in the licence number and callsign area. Ofcom are trying exceptionally hard to hide and obscure the ability to report interference!

It is very important that you ensure the interference is not coming from within your home. Ofcom will state that they levy a charge if the problem is being caused by your own device(s). They will not charge you for finding interference causing devices which are external to your property, but they will insist you acknowledge their terms and charging conditions.

Ofcom now triage calls on a 24/7 basis, so you may receive a phone call shortly after filing the complaint (unless you telephone them). Be prepared to be fobbed off on the BBC (for domestic broadcast complaints) and given the brush-off. Stick to your guns and insist on a Field Engineer visit.

Ensure you obtain a Case number for your complaint. Ask for one if they do not automatically offer it. Without the case number you have no ability to track the complaint! If you are filing complaints for multiple interference sources, ensure each source is given a case number, else Ofcom will continue to lie about the total number of complaints they receive, and the sources.

After all of that, there is no guarantee that your investigation will yield results. If the device found to be causing interference is CE marked, Ofcom will state their hands are tied and they cannot remove it from service.

Case closed

Ofcom do not like to do their job, unless it makes loads of cash! It makes their stats look bad, so they prefer to close cases without resolving the issues. They will often close the case without investigating, as that makes their complaint resolution stats look really good!

For example, if you are a Citizens' Band radio user, Ofcom will cite section 1.6 of the Wireless Telegraphy Act to justify their in-action!

Wireless Telegraphy (WT) Act licence exemption and regulatory issues

1.6 Please note: users must understand that CB radio equipment shall be operated on a 'non-interference, non-protected' basis; that is, it shall not cause harmful interference to, and shall not claim protection from, other radio services.

Of course, non-EMC-compliant electronics are not "radio services", but Ofcom do not see it that way!

If you are a Shortwave radio listener, Ofcom will forcefully insist you contact the BBC's new Radio and Television Investigation Service. If the problem is EMC non-compliance related, the BBC will send you straight back to Ofcom!

If you are a Radio Amateur, Ofcom will only investigate if you are suffering interference to the international ITU frequency allocations for radio amateurs. If the interference source is PLT or a plasma television, Ofcom will state they are powerless to act and justify it with: "it is not in the public interest [to prosecute]".


We do not have the facilities to offer EMC testing, but we have amassed a great deal of information and experience, and we can often tell the more common interference sources just by listening to a sound sample. If you can make an audio and/or video recording, our volunteers can listen/watch and offer advice on what might be causing the interference.

If you are going to make recordings, please follow these simple steps:

Audio recordings

Ensure you use Amplitude Modulation (AM) to make the recording.

Amplitude Modulation offers the widest receiver bandwidth (typically 6000 Hertz) to record the interference. If you are using a Shortwave receiver, it will already be using AM. If you are using an "FM Stereo" radio, you can only make the recording in FM, and this will suffice. Radio Amateurs and users of multi-band Citizens' Band radios should switch from FM/CW/SSB to AM before making the recording.

Leave the radio tuned to a spot frequency.

If there is a variation in the signal, altering the receiver frequency will introduce phase-shifts in the interference and this will make it harder to understand. Leave the dial tuned to a spot frequency and note it as below. Make several recordings on different frequencies if that will help.

Make a note of the frequencies you are recording and time and date stamp them with an accurate clock source.

The High Frequency bands are subject to atmospheric changes during the day. The sounds you are hearing may not be interference, but natural noise from the sun, atmosphere, or distant thunder storms; or they might be from Over-the-Horizon-Radar being used by foreign military operations in bands they should not be causing interference to. If we know the date and time of your recording, we can cross-reference it against the various Amateur Radio Intruder Watch systems to rule out known distant interference sources.

Video recordings

Pictures tell a thousand words, and videos of your radios with clear audio of the inference are an ideal way for people to analyse your issues. With video, you can tune the radio to demonstrate the extent of the interference. As outlined above, please also remember to use Amplitude Modulation (if applicable) and list the dates and times in the recording or in the comments of what ever video sharing site you prefer.


If the free open-source External link Video LAN Client can play it, we can too.

Contact us

You can contact us in a number of ways:

E-mail us via the website.

Tweet link(s) to the recordings to @UKQRM

The buck stops at the government!

If you end up running around in circles with your interference case unsolved, we recommend you use the External link WriteToThem website to write to your MP to highlight your problems with Ofcom. The mess caused by the lack of law and standards enforcement can only be addressed once MPs get rid of Ofcom and create a body who are prepared to investigate and prosecute.

Page updated: 15th August 2021

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