Hello Everyone, While we're on the subject - not to get too far off on a tangent - I have been doing 'web-research' on this - but can someone recommend a great site or reference for the specifications of the GPS signaling sent down by a GPS satellite? For instance, I learned that PPS for a military satellite and a civilian satellite are not the same thing. PPS meaning Precise Positioning Service.
Thanks and 73's, John AJ6BC (Ham call sign) On Mon, Sep 16, 2013 at 2:51 PM, Bob Camp <li...@rtty.us> wrote: > Hi > > On Sep 16, 2013, at 9:48 AM, Jim Lux <jim...@earthlink.net> wrote: > > > On 9/16/13 6:03 AM, David J Taylor wrote: > > > >> > >> I am thinking about exact time measurement - getting your PPS edge > >> exactly on the nanosecond. People can add in the length of the cable as > >> an offset, so they must also need to enter any delay through any > >> filters, mustn't they? > >> > >> Agreed that for position alone it doesn't matter as much. It's the > >> antenna's approximate position which will be measured. > >> > >> Your points about dispersion in the filter, and temperature coefficient > >> of delay are good ones. > >> > > > > > > It's trying to get nice flat group delay in the filter that causes all > the issues with Light Squared. *small*, *inexpensive* brickwall bandpass > filters tend not to have nice delay properties, or at least ones that are > temperature stable. Spectrum regulators know this, of course, and assign > adjacent services accordingly. > > > > > > If you're only worrying at the few nanosecond level, you probably don't > have to take into account continental drift (periodic resurveys of location > to account for several cm/year?) and solid earth tides (on the order of > 30-50 cm). And, really, for a lot of applications, you're interested in > relative timing, so the solid earth tide shift of 1-2 ns every day isn't a > big deal. > > Well maybe it is…. > > If > > 1) Your antenna is ~ 2 ns out of position > 2) you have a small number of sats > 3) Everything else is doing very well > > Then as you take sat's in and out of the mix, you will could get 2 ns more > "pop" than you would have otherwise. > > Bob > > > > > > > > > _______________________________________________ > > time-nuts mailing list -- time-nuts@febo.com > > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.