Unprecedented Syntonization and Synchronization Accuracy via Simultaneous Viewing with GPS Receivers; Construction Characteristics of an NBS/GPS Receiver

摘要

The NBS/GPS receiver has been designed around the concept of obtaining high accuracy, low cost time and frequency comparisons between remote frequency standards and clocks with the intent to aid international time and frequency coordination. The receiver has been tested by simultaneous viewing of the GPS satellites with the USNO GPS receiver as well as by several individual tests. The simultaneous viewing yielded syntonization accuracies of the order of parts in 10E15 over about a two-week average. Using a May '81 portable clock trip to calibrate the differential delay between the NBS and the USNO GPS receivers, July and August '81 portable clock trips agreed with the values given by simultaneous GPS satellite viewing between Boulder, CO and Washington, DC to better than the 10 ns accuracy of the portable clock trips. The hardware and software of the receiver will be detailed in the text. The receiver is fully automatic with a built in 0.1ns resolution time interval counter. A microprocessor does data processing. Satellite signal stabilities are routinely at the 5ns level for 15s averages, and the internal receiver stabilities are at the 1ns level. The second generation receiver has a built in CRT and parallel keyboard for operator interface. Serial RS232 is provided for local hardcopy (printer) and telephone modem use.