[time-nuts] GPS backup for the stationary time and frequencyuser

Matthew Kaufman 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 
> guilty...
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.

Matthew Kaufman

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