On Thu, 2008-04-24 at 13:45 -0700, Chris Kuethe wrote: > On Thu, Apr 24, 2008 at 9:14 AM, Kipton Moravec <[EMAIL PROTECTED]> wrote: > > I am designing a system with a GPS module, and started looking at all of > > the things it could do, including time. > > > > Since you folks are all interested in time, I was wondering which of two > > products would be of interest to you. > > > > 1. A GPS module with the ability to expand the serial port to more than > > 10 to allow you to use the NTP NEMA driver. The time pulse would be > > accurate to about 30 nS RMS. Retail cost about $100. > > yes. although i'm wondering where you're going to get such a > non-crappy chip. Also, will it output raw measurements (CP/PR/D)? > While you're at it, could you mount this on a (mini)?pci card with a > dual-port UART - plug it in, it looks like 2 more com ports, but then > you can use one port as your time source and the other port for > "control" purposes. >
The problem with putting it in the PC is that the PC is most often not near the sky. GPS needs some view of the sky. You loose a lot of signal with a long antenna lead, that is why you rarely see more than a 15 foot antenna lead. > > 2. A time server with 2 Ethernet ports, with GPS time reference, to > > directly support between 50 and 100 users using GPS. Retail Cost about > > $200 > > could be fun - depends on what's in it. > Just a 32-bit microcontroller with a good crystal and a GPS. All running linux. No keyboard, no monitor, just ssh to it over the Ethernet. Not that exciting. > > Both would be Stratum 1 by using the GPS (and later Galileo also) > > Satellites. > > > > Any additional specifications? How much more would you pay for the > > additional specs? > > > > Or is this not interesting enough for you, that I would be wasting my > > efforts. > > my home time server is a soekris net4801 driven by a garmin gps18; > pretty low-end, but internal diagnostics say that it's tracking within > 1 usec of the garmin's PPS output. that's tolerable, considering the > garmin is only specified to 1 usec accuracy, and the 4801 isn't really > a marvel of computing precision. And the fact that it's > ethernet-connected to the ass end of an ADSL line - there goes all my > precision anyway. > This is 30 times more accurate than the Garmin, but the PC is no where near that accurate, so it does not matter. > also, the soekris can support more than 100 users; i've seen 182 > unique ip's today, and the day is barely half over. > > as i'm also a bit of a gps nut, i like the fact that i can run gpsd on > my time server to get a view on how the GPS is performing, as well as > being able to generate a sky view (http://gpsd.mainframe.cx/). For > that matter, I like the fact that I can put perl/php/python on this > machine and whip up little scripts as it need them. So a cute little > low-power SBC would be neat, but I hope it's not too low-power... > All that will be possible, you could have access to the NEMA data. Is it important? Kip -- Kipton Moravec KE5NGX "Always do right; this will gratify some people and astonish the rest." --Mark Twain _______________________________________________ timekeepers mailing list [email protected] https://fortytwo.ch/mailman/cgi-bin/listinfo/timekeepers
