Satellite signals critical to military operations can be jammed using cheap equipment from home improvement stores and electronics fairs, a US Air Force team has found. Instructions on how to build the jammers were found on the Internet.
The team, dubbed the Space Aggressor Squadron, was set up to look for weak spots in satellite communications and navigation systems by playing the part of a potential enemy. By rummaging around websites, books and magazines, the squadron, which is based near Colorado Springs, monitors how much sensitive information is in the public domain. "We ran a search on the Net and found there's quite a lot of information out there on how to build and operate satellites but also, unfortunately, on how to jam them," says Tim Marceau, head of the squadron. "Just type in 'satellite communications jamming' and you'll be surprised how many hits you get."
To test the accuracy of the info, Marceau ordered two rookie engineers from the US Air Force Research Laboratory to build a jamming system using only a Net connection and whatever they could buy for cash. The result was alarming: for $7500, the engineers lashed together a mobile ultrahigh-frequency (UHF) high-power noise source that they could use to jam satellite antennas or military UHF receivers. "It's just like turning your radio up louder than someone else's," Marceau says.
The engineers built their home-made jammer using a petrol-driven electricity generator, wood, plastic piping and copper tubing. The amplification and noise-generation electronics were obtained at an electronics enthusiasts "swap meet".
Copper coils wrapped around the plastic pipes formed the jammer's antenna (see below), while the amplifier and generator sat beneath, powered by the generator. Loaded onto a pick-up truck, the device makes an effective mobile jammer. "For very little money and very little sophistication, we found you could muck up communications," says Marceau. Different components could be used to jam other frequencies, such as that of the Global Positioning System.
John Pike, director of space policy at the Federation of American Scientists in Washington DC, agrees there's a lot of information on jamming on the Net. "But there's still a lot more available in hard copy if you know where to look," he says.
"GPS is a very low-power signal, so to jam reception of that is simple," Pike adds. "It would take just a couple of hours to work out how to make a bubble in which GPS receivers won't work." But he doubts whether similar home-built equipment could pose any threat to modern extra-high-frequency global communications satellite clusters, which he says are "heroically resistant to jamming".
Author: Paul Marks
New Scientist issue: 22nd April 2000
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