GPS attack vector

Do you use GPS to provide any mission critical services (like time of day)
in your network?

Have you already see this? (I hadn't)

-- jra

This could also be a big show stopper for cellular and radio networks. Many
use a 10.0000000 MHz timebase distributed from a GPS disciplined local
oscillator for precise time and frequency synchronization. Without this
tight frequency stabilization from a GPS receiver, major drama will occur
on the "borders" between simulcasting repeater coverage areas, cell sites,
etc. Can anyone say Spaghetti mess? Owwwww my brain hurts.

Tom Morris, KG4CYX
Chairman, South Florida Tropical Hamboree
Mad Scientist, Miami Children's Museum

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Hi, Jay,

Yes, saw this about a month ago. We have a UNAVCO Plate Boundary Observatory station (779) on our site, and it uses a Trimble NetRS. We also use GPS timing locally to generate NTP stratum 1 for our LAN via Agilient/HP Z3816 disciplined receivers, and individual GPS receivers for both of our 26 meter radio telescopes for precision local standard of rest calculations.

But as a frequency standard for 10MHz, we only use the output of the frequency locked loops in the Z3816s as references for our Efratom rubidium standard; even cesium clocks have more drift than rubidium ones, and the rubidium is manually locked, and is the master reference for anything that needs a frequency reference; the Z3816's can have significant jitter (well, significant is relative.....). Last I checked, the rubidium was 8.5uHz (yes, microHertz) off according to the GPS disciplined 10MHz signal from one of the Z3816s (we use an HP differential counter with a very long gate time to get that measurement precision).

It was interesting timing for the release of this paper, as it was around the time tick and tock were rebooted and went all 'Doc Brown' on us.

Anyone interested in the vagaries of serious time precision, please reference the 'Time-Nuts' mailing list, and other content, hosted by