On Thu, September 9, 2010 1:55 pm, Matthew Kaufman wrote: > On 9/9/2010 10:42 AM, Ralph Smith wrote: >> On Thu, September 9, 2010 1:10 pm, Matthew Kaufman wrote: >>> On 9/9/2010 8:37 AM, Ralph Smith wrote: >>>> We have a requirement for approximately ten radio sites to be >>>> synchronized >>>> to within 30 ns of each other. >>> 30 ns seems a little closer than most radio site applications need... >>> what drives this requirement? >> Aircraft surveillance using multilateration. > So timing errors just become position errors. How do the sites talk back > to the display? Can't you null out position errors if enough sites can > see a single plane, and thus learn the timing error of the drifting > (relative to other) site?
Sites communicate via landline telco. If there are sufficient mutually visible networked sites to form a solution on an aircraft visible to stations not in the timing network that would work, and is one of the options we are studying. >>>> Ordinarily you could throw in an >>>> appropriate GPSDO and be done with it. However, we also have the >>>> reqirement to be able to operate independent of GPS for up to six >>>> days. >>> Wow, ok, and what drives *that* requirement? Can you use any other >> Paranoia. People making the requirements are concerned with GPS going >> away >> due to solar flare or some other reason. > Once everyone relies on GPS approaches and ADS-B, the planes will be > grounded long before 6 whole days of GPS outage anyway. You're making the mistake of applying logic. ;) Actually, aircraft can continue to fly VFR or navigate using VOR/DME and inertial navigation. The radios are part of an ADS-B installation. >>> mutually visible thing, or do we assume all satellites have vanished >>> from orbit? >> No satellites. >> >> > Ok then. My best answer is to use the planes themselves as the common > reference, at least the ones high enough that enough sites can see them. > > Also consider that you might be able to find additional mountaintop > sites to plant fixed squitter-emitter transponders at that can be seen > by 2 (or more) sites. Thanks, all of these are various options we are considering, considering all of the engineering trade-offs. Ralph _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
