Guidance for making inexpensive devices that can jam GPS signals

　　Information in an article appearing in the current issue of Phrack, an online hacker magazine, could put GPS devices at risk for commercial navigation and military operations.

　　The Phrack article provides a detailed guide to building a low-cost, portable GPS jammer using components readily available from electronics suppliers. According to the article, "The onslaught of cheap GPS-based navigation (or hidden tracking devices) makes it necessary for ordinary citizens to master the art of electronic warfare." Electronics and GPS experts who read the article this week say it's technically competent , and said that hobbyists with certain technical skills could build GPS jammers according to the plan.

　　Although the article says the jammer is only designed for civilian GPS signals broadcast on the 1575.42 MHz frequency, not the military frequency 1227.6 MHz.

　　While the Phrack jammer targets civilian GPS signals (known as C/A codes), it can also threaten military systems because "almost all military GPS receivers must first acquire a C/A signal" in order to lock onto military signals, It is called P(Y) code.

　　GPS receivers are particularly susceptible to interference because of low signal strength after GPS satellites 12,000 miles from Earth pass through space.

　　The impact of the homemade jammers described in the article is "somewhat severe" because the use of such jammers "may disrupt commercial operations."