In case any backroomers are near Portreath in Cornwall today and using GPS... be warned the MOD are testing effects of jamming the signal.
www.theregister.co.uk/2007/06/06/mod_gps_jamming_t.../
Might effect GPS receivers upto 11km away apparently.
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Cue the posts about how useless their satnav is without any assistance from the MOD ... (yawn)
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Yes I am within 11km Of Portreath. But knew about this anyway...
Will be keeping a watch on local news for stories of people who cannot get into their cars with remote plippers, Confused ECU's and people unable to pick up Sat Tv.
Good one to use for the future when the Gov. bring in satellite based road charging - sorry my sat system was mucked up - they must have been testing again at RAF Portreath!
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GPS is run by the US, primarily for military purposes? Yet our own little Dad's Army MOD can successfully jam it?
Do you think other countries, terrorist groups, etc already know how to do this, or will their represenatives all be visiting Portreath soon in order to observe the proceedings? Perhaps the MOD should lay on transport and accommodation for them, rather than just announcing the venue in the papers. Or are they going to post the details on the internet?
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The US use a different system which is only available to them, uses the same satellites but a different group of signals, so they wouldn't need to disturb normal signals.
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So you think the US DoD altruistically spent billions of $$$ developing GPS to give every country in the world a precision location system?
The transmissions from any visible constellation of satellites can be 'perturbed' at will from the 'ground segment', causing any desired degree of inaccuracy over that region of the planet.
However, the US would never have any recourse to do this, would it......?
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GPS suffers from (at least) two major drawbacks:
1) The received signal is very weak indeed - significantly below the 'thermal' noise level - making it somewhat prone to intentional jamming.
2) GPS was a (US) military development, hence the entire system is under the sole control of the US Department of Defense (sic). This includes both the 'commercial' system, and the military version (which operates on a different frequency). There is nothing to stop them deliberately 'falsifying' the signal over selected regions of the world - which is one reason why many countries are still reluctant to base large parts of their infrastructure on GPS, despite the improved accuracy obtained when 'selective availabilty' was switched off in the late 90's.
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So do the principles involved in jamming one not apply to the other? Why would the MOD be interested in jamming the non-military version?
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"So do the principles involved in jamming one not apply to the other? Why would the MOD be interested in jamming the non-military version?"
Don't know the answer about being able to jam one and not the other. But being in NATO means we have access to the military version anyway. So if they are testing the effects of jamming on GPS for military use, then they must therefore be testing jamming the military version as well? In fact you probably can only jam both.
There is one story where an entire harbour lost GPS signals due to a faulty TV amplifier! So it cannot be that difficult.
The GPS signal is very weak and easy to interfere with - the receiver is easily confused. It is said GPS jamming was used during the 2001 Afghan war and the 2003 Iraq war... but they apparently destroyed the jammer used in Iraq using a GPS guided bomb ;-) Ironic. But since they emit radiation then an anti-radar missile would probably work too.
The US (and select allies) also now have the Defense Advanced GPS Receiver (DAGR) which is less susceptible to jamming.
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Don't know the answer about being able to jam one and not the other. But being in NATO means we have access to the military version anyway. So if they are testing the effects of jamming on GPS for military use then they must therefore be testing jamming the military version as well? In fact you probably can only jam both.
The military use a different frequency to the civilian system, so it's easy to jam only one.
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So do the principles involved in jamming one not apply to the other?
Yes. The military implementation uses secure-key encryption, but the principles involved in jamming (rather than trying to use the system) remain the same.
Why would the MOD be interested in jamming the non-military version?
Perhaps you'd better ask them :-)
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Military and civilian GPS are on sufficiently close frequncies to be able to Jam both.
Its very easy in a local area you only need sufficient power to swamp what is a very low level of GPS reception.
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TourVanMan TM < Ex RF >
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