[NLRS] FYI - GPS Network May Experience Errors in "Week Number" Rollback

[Jon Platt]

You may have seen this notice on the ARRL's letter .... if not see the following cut and paste.   This may be significant for those of us with older GPS units used both for grid location as well as for WSJT timing. 73, JonW0ZQ  "The GPS network will encounter a small millennium bug of its own in April when the network's "week number" rolls back to zero. This known issue especially could affect those who use GPS to obtain accurate Coordinated Universal Time (i.e., UTC). In the GPS network, the number of the current week is encoded into the message the GPS receives using a 10-bit field. This allows for weeks ranging from zero to 1023. The current period began on August 1, 1999. On April 6, 2019, the week number rolls over to zero and starts counting back up to 1023.  This should not affect later-model GPS receivers that conform to IS-GPS-200 and provide UTC, but testing carried out by the US Department for Homeland Security (DHS) raised the possibility that some units may misinterpret the rollover, shifting the date back to January 6, 1980, or possibly to another incorrect date. An affected GPS not only may report the incorrect date, but time accuracy that is critical to precise location data could be compromised. A nanosecond error in GPS time can equate to 1 foot of position (ranging) error, according to DHS-published guidelines that explain the issue and suggest how to address it".