GPS week rollover issue

My old Cambridge gps had to be sent back to be reset.Â* What about the
ClearNav or PowerFlarm portable?

On 2/6/2019 10:56 AM, Jonathan Foster wrote:
Tim, thanks for that explanation. Is this what happened to the Cambridge instruments that needed an update to keep working several years ago?

On Wednesday, February 6, 2019 at 10:45:04 AM UTC-7, Tim Newport-Peace wrote:
At 17:00 06 February 2019, Jonathan Foster wrote:
I just came across this interesting page:
https://www.orolia.com/resources/blo...-you-need-know

On April 6th of this year the GPS week will roll over and on some older
instruments it could mess up the date. How many of our soaring
instruments
might have this problem?

Jonathan

Any of them, but the older instrument the more likely it is to have a
problem.

The date is transmitted by the satellite as a day oy the week and a week
number. there are 11 bits available for the week number (0-1023) and a
rollover occurs every 1024 weeks (an Epoch) or 19 years 8 months approx.

As the GPS engine in the instrument does not receive the Epoch number from
a satellite, it relies on a Battery Maintained Real Time Clock on the GPS
Engine module. If the battery fails or is allowed to become discharged,
Epoch 0 may be assumed, which it probably isn't. Epoch 0 started 6th Jan
1980 originally, but some recorders may have a different date set to fix
previous rollover problems.

The RTC battery should hold up for six months or so, but as the battery
becomes older, the capacity may decrease, reducing the figure. The best
advice seems to be to connect your instrument just before 6th April to
allow the GPS Engine battery to charge. And pray. If you Recorder has the
right date after 6th April 2019 all is well and good, but never allow the
RTC battery to become discharged.

If you have the wrong date after 6th April, it is a Return-to-Manufacturer
repair.

Good Luck!

--
Dan, 5J