GPS backup for the stationary time and frequency user
Hi
Except I suspect they have a model that uplinks to stuff pre-mounted in geo orbit over the US. I haven't been shopping for that sort of stuff in a while.....
Bob
On Oct 9, 2010, at 1:00 PM, Matthew Kaufman wrote:
But unlike the threat I described, they're not pre-mounted in geo orbit over the US... As far as we know.
Matthew Kaufman
(Sent from my iPhone)
On Oct 9, 2010, at 9:16 AM, Bob Camp lists@rtty.us wrote:
Hi
The Russians have been willing to sell GPS jammers for quite a while. They aren't terribly expensive. Their export controls are a bit different than the US's.
Bob
On Oct 9, 2010, at 12:00 PM, Matthew Kaufman wrote:
On 10/9/2010 8:22 AM, jimlux wrote:
Unlikely that this would be in the open literature. It's pretty clearly one of those things that falls under export control.
Quite likely. The threat itself hasn't been mentioned as far as I can tell, either... as someone who relies on GPS timing for several telecom and network applications, including one where time disruptions can be security disruptions, it is definitely something to think about and add to the list of risks.
Matthew Kaufman
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Bob Camp wrote:
Hi
The Russians have been willing to sell GPS jammers for quite a while. They aren't terribly expensive. Their export controls are a bit different than the US's.
Bob
Simple GPS jammers are pretty easy, since consumer GPS is very
vulnerable to repeater jammers. Hmm I wonder if that would adversely
affect a GPSDO? Probably not, since the repeated signal is just as
stable as the original one.
jammers probably aren't subject to export controls, just local usage
regulations (e.g. illegal in US because of FCC rules prohibiting them).
the ITAR (which is the big deal in the export controls world, compared
to EAR) is the International Tariff, so everyone is a signatory, and
we're all in the same boat as to what is a munition and what is not.
Granted, enforcement and interpretation varies.
On 10/09/2010 09:47 PM, jimlux wrote:
Bob Camp wrote:
Hi
The Russians have been willing to sell GPS jammers for quite a while.
They aren't terribly expensive. Their export controls are a bit
different than the US's.
Bob
Simple GPS jammers are pretty easy, since consumer GPS is very
vulnerable to repeater jammers. Hmm I wonder if that would adversely
affect a GPSDO? Probably not, since the repeated signal is just as
stable as the original one.
Well, a real jammer will just prohibit the reception of signal while a
spoofing attempt would provide a false signal. There is no reason to
assume that a spoofed signal would be stable. Also, the spoofing attempt
we talked about through the WAAS bent-pipe does not necessarily make the
GPS receiver lock onto all the spoofed signals, but a shifting selection
of correct and spoofed signals. RAIM in receivers would help to some
degree, If it fully locks on to the spoofing signal, just to be thrown
away in time and that should upset most GPSDOs quite a bit.
jammers probably aren't subject to export controls, just local usage
regulations (e.g. illegal in US because of FCC rules prohibiting them).
the ITAR (which is the big deal in the export controls world, compared
to EAR) is the International Tariff, so everyone is a signatory, and
we're all in the same boat as to what is a munition and what is not.
Granted, enforcement and interpretation varies.
Someone seriously wanting to use one for some reason would not care
significantly and found ways around it. Someone with sufficient
knowledge would build one if needing to.
Cheers,
Magnus
On Oct 9, 2010, at 12:47 PM, jimlux wrote:
Simple GPS jammers are pretty easy, since consumer GPS is very vulnerable to repeater jammers. Hmm I wonder if that would adversely affect a GPSDO? Probably not, since the repeated signal is just as stable as the original one.
I would think that with a little bit more effort, one could make a fairly simple repeater jammer that broadcasts a substantially less stable signal. With a suitable slack buffer between the receiver and transmitter, the retransmission delay doesn't need to be constant or even predictable, thus messing with apparent time and frequency. With still more effort, one could detect individual satellite signals and retransmit them separately with different and varying delays, thus messing with the apparent position relationships of the birds at any point in time.
--
Mark J. Blair, NF6X nf6x@nf6x.net
Web page: http://www.nf6x.net/
GnuPG public key available from my web page.