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Old 04 February 2008, 12:11   #1
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GPS Jamming in April

The following GPS jamming exercises, planned by the MoD have been publicised by Ofcom:

Dates: 31 March to 4 April 2008
Times: between 08:00 and 18:00 hrs
Location: To sea from Bridlington - N54 06.842 W000 05.045
Contact: Trial Manager - 07766 134758

Dates: 20-21 April 2008 (26 April 2008 reserve day)
Times: between 09:00 and 17:00 hrs
Location: To sea from The Hebrides - N57 14.4 W007 26.7
Contact (during jamming exercise only) 07766 134520

Details of the trials are "restricted", but the government has said that the trials are intended to research "vulnerabilities in a range of military applications" of satellite navigation, although is has also been noted that the Defence Science and Technology Laboratory PR team have denied that such trial are taking place!
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Old 04 February 2008, 12:36   #2
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Once upon a time they said it couldn't be jammed..........
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Old 04 February 2008, 13:20   #3
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Perhaps it couldn't. Perhaps they can't. Perhaps they're trying again.
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Old 04 February 2008, 13:25   #4
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Oh it can alright - sometimes by accident!!!
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Old 04 February 2008, 15:56   #5
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This is probably a silly question...

...but given the coordinates

Location: To sea from The Hebrides - N57 14.4 W007 26.7

it all seems a bit 'woolly' to me. How far out to sea? In any particular direction? Or 360?

I haven't got a chart for there - it is S. Uist isn't it?

I presume the technicalities involve lots of 'noise' on the correct wavelength or something? Are there any people who know stuff knocking about out there?

I think we should be told!

Then again, if it's not officially happening...

Paranoid? Me?
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Old 04 February 2008, 16:18   #6
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..I haven't got a chart for there - it is S. Uist isn't it?
Aye, it is.
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Old 04 February 2008, 17:26   #7
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it all seems a bit 'woolly' to me. How far out to sea? In any particular direction? Or 360?
last time i think they were suggesting a 6 NM radius to be at risk. It could be more powerful this time?

The site is MoD land on the west of the island. Since GPS signals don't travel well through land I think you will be fine to the East of the island.

last time round the cg were making securite anouncements.
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Old 05 February 2008, 06:50   #8
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Since GPS signals don't travel well through land
Not meaning to be rude, just curious, but I'm not sure I follow the thinking here. The GPS signals are coming from satellites, so where is the land that they would have to travel through?
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Old 05 February 2008, 09:02   #9
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Not meaning to be rude, just curious, but I'm not sure I follow the thinking here. The GPS signals are coming from satellites, so where is the land that they would have to travel through?
I am assuming if you wish to Jam a GPS (or test technology for jamming or preventing jamming) you use a ground based transmitter to broadcast a jamming signal on the frequencies used for GPS. If you either broadcast false signals or relatively high powered noise you confuse the reciever. So that it can't recieve/process the satellite signals or so that it thinks it is getting signals from a satellite which it is not. Hence the effect would only be in a localised area within line of sight of the transmitter.

Does that make sense? I suppose you could try to block the satellite itself - but you would need to either block all the satelites in an area or make a satellite send the "incorrect" signal - and that seems a lot more difficult.
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Old 05 February 2008, 09:07   #10
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In that case why do the tests at sea? If the effect wanted is to send a different signal there's no need for it to be done at sea. The results can established on land.
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