GPS Jamming

GPS jamming is a nightmare to weather balloonists tracking their payload. Jamming takes many forms, some legal and some illegal. Here I have a comment from Clive Corrie (Ofcom Head of Spectral enforcement) who gave a little insight into legal jamming. It is followed by an article on the BBC web site covering illegal jamming. In short the problem of legal seems confined to sporadic GPS jamming in specific regions by the MOD. The issue of illegal jamming of GPS by those who don’t like being tracking seems confined to areas adjacent to roads and presents an unpredictable and transient menace.

Clive from Ofcom told me, “Jammers are devices which are intended to prevent radio equipment from receiving and transmitting the signals relevant to their function.

Jammers fall into two ‘loose’ categories; blocking (emitting radio waves to overwhelm the target receiver) and so called intelligent transmitters that use radio signals to confuse or degrade the target.

Many radio applications can be the target including fixed and mobile radio communications systems and Local Area Networks, but the most common are mobile phone networks and satellite navigation applications.

Except for reasons of national security or the prevention and detection of crime, there is arguably no legitimate reason for anyone in the UK to have jamming apparatus in their possession or control. Jammers have a single intended application, the consequences of which would result in the commission of a criminal offence.

Indeed, section 68 of the Wireless Telegraphy Act 2006 (‘WTA’)  creates a criminal offence of using apparatus for the purposes of deliberately causing interference to wireless telegraphy; this carries a maximum punishment of two years’ imprisonment or/and an unlimited fine. However, this offence can be difficult to prove because it must be shown that the accused was aware that they were using the apparatus for the intended purpose. This is exacerbated by the absence of laws that prevent the possession, sale, advertisement for sale, hire, operation or importation of jamming apparatus.

The UK Electromagnetic Compatibility Regulations 2006 (‘EMC’) facilitate the free movement of electrical products in the European market. While they create an offence of placing non-compliant products on the market and this would encompass jamming apparatus, again key elements of this offence can be difficult to prove.

Under the  EMC regime  all electronic products placed on the market in the UK,  including, in theory, jammers,  are required to comply with the Electromagnetic Compatibility Regulations 2006 (Statutory Instrument number 2006/3418) (the “EMC Regulations”). This implements an EU Directive (204/108/EC). In summary, electronic equipment (which generates an electromagnetic disturbance) must only be placed on the market if it complies with certain relevant requirements. Equally, Member States must not impede the placing on the market of equipment if it does comply. The key requirement is that equipment must meet “essential requirements”. These are that the electromagnetic disturbance generated by electronic equipment does not exceed a level above which radio and telecommunications equipment or other equipment cannot operate as intended and that the equipment itself has an adequate level of immunity to electromagnetic disturbance. Clearly it would be difficult to show that a jammer meets these requirements and therefore could not legitimately be placed on the market in the UK (or EU)

The UK Government department for Business Innovation and Skill (BIS) is responsible for overseeing the EMC Regulations. Enforcement powers are delegated to Ofcom where there is a radio spectrum protection or management issue. Ofcom can bring criminal prosecutions and can suspend sales if it believes an offence is taking place. In connection with our functions we engage with BIS, the EU Commission’s Directorate General (DG) Enterprise and other Member States through Administration and Cooperation Groups (ADCO).

We undertake proactive market surveillance with the aim of removing jammers from the market in the UK and enjoy the cooperation of other agencies and internet sales platforms. Where necessary we take enforcement action which may include prosecuting offenders.

We also work in cooperation with the government and police (through the Association of Police Officers).

Some jammers advertised for sale on the internet are shipped directly to customers from the supplier outside the UK or EU making enforcement problematic.

Sections 62-67 of the WTA enable Ofcom to make an order imposing restrictions on apparatus to prevent or reduce the risk of interference with wireless telegraphy. Such restrictions can make it an offence to:

manufacture apparatus (whether or not for sale);

sell apparatus or offer it for sale;

let apparatus on hire or offer to let it on hire;

advertise willingness to sell apparatus or let it on hire;

have custody or control of apparatus; and/or

import apparatus.

The Secretary of State must approve Ofcom’s making of an order, and a statutory instrument containing an order can be annulled by either House of Parliament. In order to make an order, prior approval from the European Commission would also be necessary under the EMC Directive and/or Technical Standards Directive. Ofcom are currently looking into the feasibility if implementing such an order in relation to jammers.

The Ministry of Defence conduct occasional tests on military systems which may result in some loss of service to civilian users of the Global Positioning System (GPS) including in-car navigation devices and networks which rely on GPS signals. Ofcom seeks to provide citizens and consumers with information about possible interruptions to these services. It must be emphasised that this notification process only warns of future jamming exercises that are brought to the notice of Ofcom and may not cover all jamming exercises. It cannot be assumed that any loss of service is due to jamming exercises.

If you would like to receive notifications of jamming exercises please subscribe  to Ofcom’s email notification service using the following link:

If you have any queries regarding these notices forward them to Ofcom @

Illegal Jamming from

The illegal use of Global Positioning System (GPS) jammers in the UK has been revealed in a groundbreaking study.

GPS jammers are believed to be mostly used by people driving vehicles fitted with tracking devices in order to mask their whereabouts.

In one location the Sentinel study recorded more than 60 GPS jamming incidents in six months.

The research follows concern that jammers could interfere with critical systems which rely on GPS.

The team behind the research believes it is the first study of its kind in the UK.

Its findings will be presented at the GNSS Vulnerability 2012: Present Danger, Future Threats conference held at the National Physical Laboratory on Wednesday.

Road watch

The Sentinel research project used 20 roadside monitors to detect jammer use.


“Start Quote

The next step is to develop the system further so that it can be used for enforcement”

Bob CockshottICT Knowledge Transfer Network

“We think it’s the only system of its kind in the world,” Bob Cockshott of the ICT Knowledge Transfer Network and organiser of the conference told the BBC.

The sensors recorded every time a vehicle with a jammer passed by.

“We believe there’s between 50 and 450 occurrences in the UK every day,” said Charles Curry of Chronos Technology, the company leading the project, though he stressed that they were still analysing the data.

He told the BBC that evidence from the project suggested that most jammers were small portable devices with an area of effect of between 200m and 300m.

The project received £1.5m funding from the Technology Strategy Board and involved a number of partners including the Association of Chief Police Officers (ACPO).

Mr Curry said the research had also resulted in the detection and confiscation by the police of one jammer.

“We detected a pattern and they [the police] were able to go and sit and wait,” he said.

Mr Curry said the research was also able to establish that jammers were responsible for interference experienced by Ordnance Survey equipment.

GPS jammers are widely available online, one reason Mr Cockshott believes the law around jammers needs tightening.

He thinks the Sentinel project should now work towards developing systems that will help catch those using jammers.

“The next step is to develop the system further so that it can be used for enforcement, so that you can detect a jammer in use and then relate it to the driver that’s using it,” he said.

Car headlight

Logistics and other companies often install GPS trackers so they can follow the movements of vehicles.

They are also used so vehicles carrying valuable loads can be tracked.

Researchers believe most GPS jammers are used to stop these devices working.

“A GPS satellite emits no more power than a car headlight, and with that it has to illuminate half the Earth’s surface,” Prof David Last, a past president of the Royal Institute of Navigation, told the BBC.

“A very, very low power jammer that broadcasts on the same radio frequency as the GPS will drown it out.

“Most of them are used by people who don’t want their vehicles to be tracked,” he said.

But the jamming technology can cause problems for other safety-critical systems using GPS.

In mobile phone and power networks GPS satellite signals are sometimes used as a source of accurate timing information.

GPS is even used to provide accurate time information for some computerised transactions in financial markets.

And other GPS navigation devices used by ships and light aircraft could also be affected by jammers.

In 2009 Newark airport in the US found some of its GPS based systems were suffering repeated interference.

The problem was eventually traced back to a truck driver using a GPS jammer

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