[time-nuts] Lost GPS lock or 1PPS recently?

Tue Sep 4 19:21:35 UTC 2018

The following are active GPS NOTAMs.
Data Current as of: Tue, 04 Sep 2018 19:16:00 UTC
GPS   GLOBAL POSITIONING SYSTEM [Back to Top] !GPS 09/009 (KNMH A0020/18)
GPS NAV PRN 02 OUT OF SERVICE 1809061455-1809070255

ZAB   ALBUQUERQUE (ARTCC),NM. [Back to Top] !GPS 08/259 (KZAB A0367/18) ZAB
NAV GPS (WSMR GPS 18-20) (INCLUDING WAAS, GBAS, AND ADS-B) MAY NOT BE AVBL
WI A 359NM RADIUS CENTERED AT 333345N1063840W (TCS054036) FL400-UNL, 311NM
RADIUS AT FL250, 215NM RADIUS AT 10000FT, 223NM RADIUS AT 4000FT AGL, 169NM
RADIUS AT 50FT AGL DLY 1830-2230 1809031830-1809082230

ZDV   DENVER (ARTCC),CO. [Back to Top] !GPS 08/260 (KZDV A0287/18) ZDV NAV
GPS (WSMR GPS 18-20) (INCLUDING WAAS, GBAS, AND ADS-B) MAY NOT BE AVBL WI A
359NM RADIUS CENTERED AT 333345N1063840W (TCS054036) FL400-UNL, 311NM
RADIUS AT FL250, 215NM RADIUS AT 10000FT, 223NM RADIUS AT 4000FT AGL, 169NM
RADIUS AT 50FT AGL DLY 1830-2230 1809031830-1809082230

The military does testing that can cause GPS jamming down in New Mexico.
Are you within range of these NOTAMS?
You might have to plot the Lat-Long co-ordinates

--- Graham

==

On Tue, Sep 4, 2018 at 1:10 PM Scott McGrath <scmcgrath at 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 <jsloan at 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
> jsloan at diag.com        http://www.diag.com <http://www.diag.com/>
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