> I think the method is still in development and Doug Hogarth is helping.
As someone else mentioned, the Z-12 receivers are discontinued and no longer supported by Thales. They do work well and are used widely, and I believe an individual in England still considers repairing them. Cost was in the $20K range and it cost something like $5K extra for the timing-specific option. Compared to typical dual-frequency carrier-phase receivers, a few key differences of the Z-12T are: 1) the receiver has a 1PPS *input* which is used to sync the receiver's timing to a reproducible zero-crossing of the reference frequency, 2) in the case of the Z-12T the input frequency of 20MHz is more directly used by the receiver, 3) the precise timing community conducts experiments with the receiver such as absolute and/or relative calibration (and comparison to other methods such as common-view and/or TWSTT). Note that Javad has similar carrier-phase timing capability but might not have as many experiments/calibrations. People like me don't use the 1PPS out from receiver, rather we supply our best clock's frequency to the receiver and log RINEX data with carrier phase. The data from similar receivers around the world including H-masers at various national timing labs is combined and processed regularly by IGS analysis centers. They produce precise orbits and satellite clocks and "ensemble" time, and the final result is that you can get a difference between your clock and one of the other clocks, typically a point every five minutes available a couple weeks after real-time. Saying "experiment" is mostly because common-view has been so widely accepted over the years, and expensive TWSTT (Two-Way Satellite Time Tranfer) is more widely accepted for higher precision. Not so many people trust the carrier-phase method but it works well for me; similarly I'm part of JPL's "real-time" system which gives me difference between my clock and AMC every second with just a few seconds delay. So to be clear, this is not typical inexpensive code-based single-frequency "one-way" GPS timing; the carrier-phase data is often used in other products such as precise orbits/clocks (which are used by geodetic community). _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
