Scott & John, Do either of you have any activity by "Light Squared" (or whatever it's now called) in your area. Jamming does not always have to be in-band to be effective.
Dana On Tue, Sep 4, 2018 at 1:11 PM Scott McGrath <scmcgr...@gmail.com> wrote: > My TrueTime DC-XL has lost lock since yesterday as has my Z3805 and my > car’s onboard GPS will not lock since the 2’nd. I need to get about a mile > from home before Car’s nav system reports ready. > > There has been a great deal of repair work on the local cable system so > this is almost certainly related to that > > But it proves my point about the fragility of GPS > > > > > > On Sep 4, 2018, at 12:31 PM, John Sloan <jsl...@diag.com> wrote: > > Folks: > > GPS jamming and spoofing isn't really my area of expertise, but it's > something I worry about, not just for its impact on geolocation and > navigation applications, but also because GPS has become critical as a high > precision timing reference in the telecommunications realm, which *is* my > area of expertise. > > Yesterday (2018-09-03) afternoon (about 22:00UTC, 16:00MDT) I noticed one > of my three home-made GPS-disciplined NTP servers had lost its GPS lock. > After some forensics on my part, this (2018-09-04) morning (about 16:00UTC, > 10:00MDT) I replaced the amplified antenna, and the device reacquired its > lock. I figured it was just an antenna failures; this is an amplified > filtered antenna so it has active electronics. > > Then just an hour or so later, I noticed one of my commercial > GPS-disciplined NTP servers (TimeMachines) had lost the GPS 1PPS timing > signal, but indicated it still had GPS lock. (I question now what this > actually means in the context of this particular device). As a > troubleshooting step, I power cycled the device, and it reacquired 1PPS. > But as I did that, the second commercial GPS-disciplined NTP server > (Uputronics) right next to it lit up with a red warning on its display, > indicating it had lost GPS lock. A minute or so later it also reacquired > lock and indicated 1PPS, with no action on my part. > > All of these devices are completely independent, have different software > (and probably hardware), have separate amplified antennas sitting side by > side in the window of my home office, and are not all on the same > electrical outlet (but may be on the same household circuit). > > I lit up the LCD display on my little GPS monitoring tool I built that > runs Lady Heather 24x7 and see on the graphical display sudden jumps of > reduced timing accuracy of a factor of 10^2 (from nanoseconds to hundreds > of nanoseconds) in the recent past. But I’m thinking this can also be > caused just by the dynamic satellite geometry, and might be normal. It’s > not like I watch this graph all the time (even though it does sit right in > front of me on my desk). > > No clue what's going on in my suburb near Golden Colorado. But I’m a > little freaked out. Trying to figure out which rule, [1] It’s something > stupid I’ve done, or [2] I am not unique, to apply. > > :John > > -- > J. L. Sloan Digital Aggregates Corp. > +1 303 940 9064 (O) 3440 Youngfield St. #209 > +1 303 489 5178 (M) Wheat Ridge CO 80033 USA > jsl...@diag.com http://www.diag.com <http://www.diag.com/> > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.