> Does this mean that by "using carrier phase disciplining techniques" > One could get two orders less noise than is shown > on the SRS page#3 graph > http://www.thinksrs.com/downloads/PDFs/Catalog/PRS10c.pdf
Warren, Yes, high-end survey equipment and metrology-level GPS timing receivers are based on carrier phase rather than code phase. But you'll rarely see this implemented as a GPSDO (I know of one and it's obsolete). Instead, for this class of receiver the local lab frequency standard (e.g., cesium or maser) is used to drive the receiver's clock and what you get out are a series of internal phase measurements. These are often batched up daily and then other non-realtime corrections are applied. What you get in the end is a precise measure of how good your local standard *was*. There's no reason in principal that a carrier phase GPSDO would not work. But I think you quickly run into other limitations that dominate the net accuracy. Like SV clock errors, orbit errors, and ionospheric corrections, etc. For fullest accuracy these all have to be applied after-the-fact (because they are not known well enough in realtime). Remember also that the GPS signal, as received by you (no matter how fancy the receiver), is not a perfect copy of UTC time as transmitted by the satellites, which in turn is not a perfect copy of UTC(USNO), which in turn is not a perfect copy of UTC. /tvb _______________________________________________ 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.
