415. Interference with global navigation satellite systems (e.g. GPS)
A new consortium will investigate problems associated with interference, jamming, and multi-path activity affecting the integrity of GNSS applications. Chronos Technology, the National Physical Laboratory (NPL), and Bath University — all of the UK — have formed the Saturn Consortium to better understand the local availability and integrity of GNSS transmissions and the susceptibility or immunity of GNSS applications to external interference.
The Saturn consortium proposes to assess the susceptibility of GNSS applications to external interference and multi-path problems, which all three members have experienced. It aims to develop cost-effective techniques to assess local availability of GNSS transmissions, and to define new standards for Galileo integrity and availability at the point of use.
In a timing environment, local signal authentication will help to improve the efficiency of the new generation of telecommunications and wireless technologies such as TETRA, WCDMA, and Wi-Max, which require precise time synchronization for capacity and bandwidth optimization. Techniques developed by the consortium will be applicable to Galileo as the new system comes into service.
(Copied entire from: “Group Forms Over Interference”, GPS World, February 1st, 2007, http://www.gpsworld.com.
According to https://www.jpl.nasa.gov, GNSS stands for Global Navigation Satellite System. Currently operating GNSS’s are GPS (U.S.A.’s Global Positioning System) and GLONASS (Russia’s Global Navigation Satellite System). Another GNSS planned for the future is Europe’s Galileo.)
416. Alarming Microwave
Question: If we use our microwave oven for longer than about 30 seconds, our car’s alarm goes off. Why? The car is at least 20 metres away through two walls. The inside of the microwave is a little corroded and the car has a remote central locking/alarm system.
Reply #1: Certain car alarms, such as those fitted to recent Mazda 6, Toyota Rav4 and Mitsubishi Shogun models, transmit a continuous signal at 2.45 gigahertz at powers of up to 500 milliwatts. The microwaves are picked up by sensors inside the vehicle, which detect changes in intensity to signal the presence of intruders. Microwave ovens also operate at 2.45 GHz. While the power radiated within the oven is typically in the range 600 to 800 watts, the amount radiated outside the appliance will typically be less than a watt. When your oven is in operation, the microwaves reaching your car may be powerful enough to trigger the sensors inside it, which the alarm system interprets as a disturbance within the vehicle.
It is possible to set a car alarm so that the internal signal generator is disabled. You might also want to have your microwave oven serviced in case there is a serious leak of radiation. If your microwave has damaged shielding the radiated power could be higher than the values above. (From Joel Smith, Pateley Bridge, North Yorkshire, UK.)
Reply #2: It is odd that your microwave is leaking enough radiation to trigger the car’s alarm, considering the legal limit – in the US, at least – for leaked radiation from a microwave oven is 1 milliwatt per square centimetre at a distance of 5 centimetres (seems a little low – shouldn’t that be 1W/sq cm? – Editor).
Perhaps your microwave has a serious leak, or you have an unusually sensitive car. You could try parking the car in front of a friend’s house and running their microwave oven to see what happens. If it appears to be solely your problem, consider getting the microwave replaced. (From Alex Reinhart, Boerne, Texas, US.)
(Copied entire from the ‘Last Word’, New Scientist, 3 Feb 2007, page 93, http://www.newscientist.com. Also see Banana Skin No. 35.)
The regular “Banana Skins” column was published in the EMC Journal, starting in January 1998. Alan E. Hutley, a prominent member of the electronics community, distinguished publisher of the EMC Journal, founder of the EMCIA EMC Industry Association and the EMCUK Exhibition & Conference, has graciously given his permission for In Compliance to republish this reader-favorite column. The Banana Skin columns were compiled by Keith Armstrong, of Cherry Clough Consultants Ltd, from items he found in various publications, and anecdotes and links sent in by the many fans of the column. All of the EMC Journal columns are available at: https://www.emcstandards.co.uk/emi-stories, indexed both by application and type of EM disturbance, and new ones have recently begun being added. Keith has also given his permission for these stories to be shared through In Compliance as a service to the worldwide EMC community. We are proud to carry on the tradition of sharing Banana Skins for the purpose of promoting education for EMI/EMC engineers.
