Re: Can GPS be 'turned off'?

From: Dave Emery (
Date: Fri Apr 15 2005 - 19:47:50 EDT

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    On Fri, Apr 15, 2005 at 06:21:52PM -0500, Brandon Galbraith wrote:
    > It really depends on your definition of "turn off". Selectively
    > availability can be turned on and off by region (which affects the
    > civilian GPS signal). It should also be no problem for the Air Force
    > to shut down the signal completely on a per region basis, but I doubt
    > there would be a region they would want to shut down the military GPS
    > signal as well as the civilian signal. For more information, read up
    > at this excellent Wikipedia article:
    	It should be noted that if civilian GPS was turned off in North
    America and probably much of, if not most of the rest of world there
    would be a lot of collateral damage to the telecommunications
    infrastructure done.
    	Many many current communications systems depend on GPS based
    timing and frequency reference in order to operate or operate at full
    capacity and service quality.
    	Systems using this range from many CDMA based cellphones, to 
    public safety trunking, to wide area paging, and to at least some fiber
    based sonet rings (the basic technology of modern fiber long distance
    telephone and Internet communications).
    	Some of these systems have local references that can handle a
    few hours of GPS outage before they wander out of spec, a few others have
    backup modes that do not depend on GPS but rather local rubidium or Cesium
    standards, and one suspects there are also a few that would fall over dead
    quite quickly if civilian GPS were turned off...
    	And this does not even start to count the people who depend on
    GPS for navigation in various ways.
       Dave Emery N1PRE,  DIE Consulting, Weston, Mass 02493
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