Even in South Korea, it was damaged by such disturbing radio waves. It was a day in San Diego, California at noon. When the airport administrator tried to monitor the aircraft entering the airport, he noticed that the system was not working properly. At about the same time, at the Naval Medical Center, the pocket bell for emergency calls to the doctor stopped working. The port traffic management system has also become unavailable. In the city, people who tried to use mobile phones noticed that the radio waves were not connected, and banks were unable to withdraw cash from ATMs. The turmoil lasted for two hours.
This mysterious incident occurred in January 2007 and it took three days to find out the cause. The reason is the training conducted by the Navy in the Port of San Diego. The Navy blocked radio signals and tried to test how to deal with communication interruptions. At that time, I inadvertently blocked the radio signals sent by GPS satellites to certain areas of the city.
In why, when the GPS signal is blocked, does this confusion occur?
In fact, GPS satellites no longer just send location information to car navigation systems. GPS has become an invisible tool, and we rely heavily on it without knowing it. The cell phone company uses GPS time information to connect the cell phone to the tower. Power companies also use GPS to synchronize multiple grids. Banks and stock exchanges use it as a time stamp to prevent fraud. Society's dependence on GPS is increasing year by year. Some people worry that they may be overly dependent on vulnerable technologies. You don't have to do anything special, such as naval training to make things happen in San Diego. You only need a GPS Jammers.
The GPS jammer is a plastic device that is sized to fit on the dashboard of a car. For example, it can be purchased online, and truck drivers who do not want its boss to monitor its whereabouts can use it. The machine has caused problems at airports, and cell phone signals have also been blocked in some cities. A jammer can block GPS within several kilometers. As a result, researchers all over the world are doing their best to prevent GPS interference.
"Weak signal" is a weakness
GPS is Power ed by radio signals from satellites. It is sent by the NavStar network (a group of US military satellites). At least 24 satellites are in operation all the time, and at least 4 can be seen anywhere on earth. Each satellite always sends its position and time measured by the atomic clock. The GPS receiver compares it with its own clock and calculates the distance to each satellite. When the GPS receiver locks on at least four satellites and calculates the time difference, it will know the exact location. Currently, many receivers use GPS as a cheap and accurate mechanism.
David Last, former chairman and consultant of the Royal Navigation Society, said: "The problem is that the GPS signal is very weak. It's like the headlights of a car 20,000 kilometers away." However, due to the limited energy supply of satellites , It is difficult to make the signal stronger. Finally, experience firsthand how easy it is to block GPS signals and how it affects current technology. In 2010, he boarded the 500-ton THV Galatea ship in the North Sea and conducted experiments. Galatea is the pride of the fleet and has the latest navigation equipment. Finally, a simple jammer emits noise at the same frequency as GPS satellites to understand what Galata can do without GPS.