GPS Epoch Rollover Findings
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:
-???? 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
-???? 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
EchoLink: ?? Node #?? 14400?? [Think bottom of the 2-meter band]
Home Page:?????????????????? http://wa8lmf.net
Live Off-The-Air APRS Activity Maps
Long-Range APRS on 30 Meters HF
DENNIS PEPLER <dgpmgpepl@...>
Garmin GPS60 also works, which was a surprise given that I've had it for twelve years and it wasn't the latest tech when I bought it.