[aprssig] GPS Epoch Rollover Findings

[Matthew Chambers]

Here, my (really old) Tom Tom still kinda works but takes an eternity to
get a lock, and has a lot of slop now it's location, in that it appears
that I'm wondering all over even while sitting still, and it won't keep
time, I've had to correct the time on it now the last couple times I've
used it.

My Byonics GPS2 puck that came with my TinyTrak 4 appears to be working, in
that the TT4 is showing good GPS and it's beaconing, but due to lack of
coverage, I have yet to get digipeated and relayed into APRS-IS so I can
see what it's actually doing.


Matthew A. Chambers, NR0Q




On Wed, Apr 24, 2019 at 11:52 AM Stephen H. Smith via aprssig <
aprssig at lists.tapr.org> wrote:

> GPS expresses the current time and date with a?? series of binary
> counters.?? This included a 10-bit binary counter for the current week,
> meaning that it could only count 1024 (decimal) weeks (just under 20 years)
> before rolling over from 1111111111 to 0000000000, and starting over.??
> This 1024-week cycle is known as an "epoch".?? The previous epoch ended on
> April 6th of this year.?? As of April 6th, a 16-bit counter for weeks
> replaced the 10-bit one.?? This change will put off the NEXT epoch rollover
> for 65,535 weeks - about 1200 years.
>
> Some older GPS hardware (actually firmware) couldn't handle either the
> rollover from 1023 back to 0000, or couldn't handle the new longer 16-bit
> counter format.?? Such devices quit working on April 6th of this year.??
>
>
> Now that the GPS equivalent of "Y2K" (April 6th) has come and gone, here
> are my findings testing a bunch of older GPS hardware.
>
>
> -???? Radio Shack "DigiTraveller" (a faceless serial puck-type device that
> looked like a flying saucer) -?? DIED
>
> -???? Holux GM-200?? USB-connected faceless mouse-type device - DIED
>
> -???? Rand McNally serial mouse-type device - DIED
>
> -???? 2nd-gen Delorme Earthmate small yellow unit with interchangeable
> serial and USB cables (not the original large Earthmate) - DIED
>
> The Holux and Rand-McNally are visible in this pic on my website:
> ???????? <http://WA8LMF.net/aprs/GPS-Antenna-Farm.htm>
> <http://WA8LMF.net/aprs/GPS-Antenna-Farm.htm>
>
> -???? Tri-M "Super Skymaster"?? white hard-mount combo antenna/receiver
> (shown in the inset photo of the above pic) survived and WORKS.?? This is
> especially amazing, given that it was the oldest of all these units.
>
> - ?? Globalsat BC-337 compact flash/PCMCIA unit - DIED??
>
> -???? Garmin Foretrex 201 wrist-wearable that is actually a repackaged
> version of the classic yellow Etrex - WORKS
>
> -???? Globalsat BU-353 (USB) and BU-355 (serial) mini-pucks available for
> USD $30 on Amazon - WORK
>
> -???? Various unbranded generic units based on uBLox G7 chipset - WORK
>
> -???? Internal GPS of Kenwood TH-D72 APRS handheld - WORKS
>
>
> __________________________________________________________________________________
>
> \Stephen H. Smith?????? wa8lmf (at) aol.com
> Skype:?????????????? WA8LMF
> EchoLink: ?? Node #?? 14400?? [Think bottom of the 2-meter band]
> Home Page:?????????????????? http://wa8lmf.net
>
> Live Off-The-Air APRS Activity Maps
> ???? <http://wa8lmf.net/map> <http://wa8lmf.net/map>
>
> Long-Range APRS on 30 Meters HF
> ???? <http://wa8lmf.net/aprs/HF_APRS_Notes.htm>
> <http://wa8lmf.net/aprs/HF_APRS_Notes.htm>
>
>
>
>
>
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>
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