[time-nuts] GPS backup for the stationary time and frequencyuser
matthew at matthew.at
Sat Oct 9 15:08:18 UTC 2010
On 10/9/2010 8:00 AM, Magnus Danielson wrote:
> Hmm. Yes. Creative! Once demonstrated essentially all WAAS/EGNOS/SBAS
> sats need to develope some protective measure.
Unless, of course, such protective measures already exist. I can think
of several ways right off the top of my head... one would be to have the
transponder be able to shut itself down if it doesn't appear to be
relaying a single valid code stream... another would be to have ensured
that the maximum power density was low enough that anything with enough
real satellites in view couldn't be practically interfered with...
another is to have ground-based monitoring and a transponder enable
system that can't simply be jammed into the "on" mode but rather
requires a key be sent require regularly to keep the transponder powered
I just haven't seen anything in the literature noting that the threat
had been looked at and/or addressed in any way.
> To pull it off, a standard GPS simulator and some minor frequency
> conversion is needed. Should not stop the handy man.
> It would be an interesting legal aspect to attempt to charge the
If there's >1 space-based receiver on the uplink frequency, you can
fairly easily find any source that has an uplink beam wide enough to
illuminate more than one of them. Failing that there's other ways to
find the source that take longer. Once found, I think there's adequate
law and precedent for going after someone who interferes with
safety-of-life transmissions. But there could be quite a bit of damage
(even as simple as lost productivity from truck drivers who couldn't
make timely deliveries until they found some printed maps) in the meantime.
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