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Author Topic: Can beacons be reflected to look like they are coming from somewhere else?  (Read 1573 times)

Offline thedoc

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Paul asked the Naked Scientists:
I am wondering if "pings" from an omnidirectional beacon can be reflected off underwater mountains, etc , such that by the time it is received it appears to be coming from a different direction. We all know about shadowing on TVs being caused by a reflected signal reaching the TV aerial slightly later than the direct signal.
What do you think?
« Last Edit: 02/07/2014 13:30:01 by _system »


Offline McKay

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No replies for this yet? Hmm.
This reminds me of a though I [and, probably, many more people] have thought about: can we, and SHOULD we fake an alien signal coming from deep space, perhaps even a concrete solar system or even a planet?
Why would anyone want to do that? Well, a common, other worldly goal or, perhaps, even a threat could do a great job unifying our planet, putting our petty differences and problems in scale..

Offline syhprum

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During WWII the signals used by the Luftwaffe to guide their bombers was interfered with so that they bombed the wrong target

Offline evan_au

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If you know the signal that is to be emitted by the beacon, well before it reaches the detector, you have a chance to generate a stronger signal coming from somewhere else.
If you have to wait until the genuine ping reaches the jammer, you can record it, and replay it at a later time or in a different location. But this means that the jamming signal will only appear further away than the genuine signal.
Knowing the signal in advance means that the jamming signal can look closer to the receiver, and be more powerful, making it look more genuine than the real signal.

If the ping is a simple beep, that is easy to duplicate.
If the ping is encrypted (such as with public-key cryptography), that is considerably harder to spoof. But it also requires a lot more processing power to generate and validate.

To minimise the chance of jamming and false detection, receivers will use directional antennas, and take measurements from different directions to triangulate the position of the beacon (or the jammer).

Offline Expectant_Philosopher

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Ventriloquists can effectively "throw" their voices.  The voice seems to come from a source other than the origination point.  The art of the performer is to form the sound as to be plausible that it is coming from the intended origination point.  To carry the same out with the underwater ping you'd want to minimize the signal from the true source and intensify the reflected path.  Temperature inversion and ducting might enable the characteristics necessary.  Temperature inversion to block the direct from source signal and ducting to intensify the reflected signal.

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