Electronic Weapons: Crossed Signals


December 9, 2010: Recently residents of Bremerton, Washington State (northwest U.S.) were warned they may have problems with wireless electronics (especially garage door openers and keyless care remotes) as the U.S. Navy tests electronic systems on the carrier USS Stennis. The ship has undergone some refurbishment recently at a Bremerton shipyard, and the electronic systems need some testing before the ship puts to sea.

This is not a new problem, which is why the navy put out a warning this time. Six months ago, the U.S. held naval exercises off Hawaii. But first, many of the ships involved tested electronics while docked, before going to sea. That’s when all the reports came in about garage door openers in the area not working. It was interference from the military electronics. But no prior warning was put out. Someone should have known better. Even new civilian broadcasting equipment can be a problem. Late last year, U.S. military personnel and their families in Japan were warned not to use a number of American wireless devices (baby monitors, cordless phones and so on), because they use frequencies too close to those allocated to cell phone service in Japan.

But it’s military electronics, which usually don’t operate near a lot of civilians, that cause the most difficulties. This sort of thing can be traced back to decisions made years ago, that have only recently turned into a problem. For over half a century, one of the radio frequencies reserved for military use in the United States (380-400 megahertz band), was also used for some consumer electronics. Starting in the 1980s, manufacturers of garage door openers were allowed to use the 390 megahertz frequency, because the openers were very short range (low power) and unlikely to interfere with military radios (or vice versa). But a new generation of military radios has changed all that, by sending out a very powerful 390 megahertz signals. Six years ago, garage door openers were sudden being activated by the new military radios in the United States.

The problem first showed up as new military radios, using the 390 megahertz frequency, were installed on military bases. By now, most bases are using the new radio system. While the Department of Defense believed that the new radios only made garage door remote control systems inoperable, thousands of users reported seeing garage doors open and close by themselves. While the garage door system manufacturers were using the 390 megahertz frequency unofficially (but with the knowledge of the government), they had to change their equipment to use another frequency. But before the gear using the military frequencies could be replaced. Over 50 million garage door systems (those within 80 kilometers of a military base), were involved in the mysterious malfunctions.

There are increasing problems like this, as more wireless equipment comes into use, and the military makes more use of frequencies they have long “owned” but not really worked hard. It's an old problem, and was first noted on a large scale during the 1991 Gulf War. Here, there was a large concentration of military equipment from all the American military services, and foreign armed forces as well. There were several unexpected incidents where frequencies collided in unexpected ways. There was some of this again in Iraq after 2003. There will be more conflicts like this, and some of it will be in combat, with deadly results.





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