Time and frequency users' manual

NIST time and frequency radio stations :

“…It was determined that the typical delay from the TCGs to the antenna system is about 17.1^s, as shown in Table 5 [79] which is similar to the ±2 cycle ambiguity figure published elsewhere [74] [57]. If both calls are routed through the same phone circuit, the delay through the circuit (type B uncertainty) should be the same for both calls.…”

Framework for cyber-physical systems: volume 3, timing annex

“…Achieving 10 -11 accuracy required careful selection of tracking times and a very stable reference; a data set taken in Maryland of the WWVB signal transmitted from Colorado is shown in Fig. 11 [47] For use as a GPS backup in Assisted Partial Timing Support (APTS) there are several new conditions that offer opportunities [46]. In WWVB receivers, options include modern hardware to improve accuracy and stability of reception, and the use of GPS to characterize the WWVB signal, requiring only stability to hold precision time.…”

“…NIST still broadcasts these timing signals: LF signal WWVB on 60 kHz, and HF signals WWV and WWVH on 2.5, 5, 10, 15, and 20 MHz [47].…”

“…Regarding methods of GPS backup for time and frequency synchronization, this section presents the status [46][47] of the 60 kHz timing signal, WWVB, of NIST. In particular, this signal may be useful to assist in holding 1 microsecond in circumstances where GPS is generally available to calibrate it, but might be unavailable for short periods depending on the accuracy required, the distance to the transmitting station and the availability of nearby reference stations.…”

“…Framework for Cyber-Physical Systems: Volume 3, Timing Annex 47 • A diversity of network paths, devices and grandmaster sources can also mitigate certain attacks. A redundant grandmaster with rubidium can provide holdover of UTC time to within a day and sometimes up to a week depending on how long the rubidium clock was disciplined by the GPS receiver.…”