Re: GPS trackers - a potential weapon from hell

<zwsdotcom@xxxxxxxxx> wrote in message
news:1140751004.459348.46320@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Joel Kolstad wrote:
The right countermeasure is a strong beacon on the GPS frequencies.

This is a good way to forefit a very large chunk of change or spend a lot
of
time in jail if you're caught; there's enough commercial usage of GPS
signals

Not really. Consider the field strength of the satellite signals on the
ground. You only need to keep your jamming signal say 6dB above that
point, within a radius of a few meters.

Since the OP up there says "strong beacon," I took his intention as jamming
over a large radius using plenty of power. I agree that conceivably you can
build a jammer that's low enough power to only block GPS reception within a
radius of a few meters.

Exactly the same principle as the FM
car-radio-adapter devices used for iPods and such; they are strong
enough to override a local station within your vehicle, but are barely
audible a few meters away.

There are many such devices that aren't powerful enough to override strong
local stations stations. If you check out some posts about satellite radio
receivers (nearly all come with FM transmitters), you'll see plenty of people
asking about which have strong enough transmitters such that they won't have
to re-tune as they drive through different towns and get "stepped on" by the
locals.

Whether the problem is due to poor design more so than hitting the legal limit
for unlicensed transmitters I don't know, however.

It's also possible to locate the bug using a passive scanning device,
because it is transmitting position data back home on some uplink
frequency.

Sure, although depending on the transmitter architecture, this could be
anywhere from trivially easy to nearly impossible. If it's using the
commercial cell phone infrastructure to send back SMS signals, it probably is
pretty straightforward.


.

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