I run a set of microwave beacons on a remote site that transmit data modes whose Tx timing is controlled from GPS. They were installed some 20 years ago and used a Garmin GPS25-LVS module to deliver NMA and 1 PPS signals to all five individual controllers.
After a power outage that lasted a couple of days, the beacons fired up but it was clear, after a couple of days timing was corrupted. Each beacon has slightly different controller firmware, and by monitoring the resulting corrupted modulation it could be determined what was wrong. No PPS signal was present - which killed modulation on two of them. NMEA timing data was present but the time being reported was out by several seconds, rendering the data signal transmitted undecodable by most people. I went up to the remote site to recover the old hardware and am in the process of replacing the timing source using a Ublox NEO-6. Since all the beacons were originally designed based on 4800 baud NMEA, the Ublox was set for this for backwards compatibility with the Garmin and the configuration saved in NV ram. Now the query I have. I had assumed it was a 1024 week rollover that killed the Garmin, but on testing teh module when I returned home, after a longer than normal initialisation period it DID start outputting the correct date and time, with PPS present. So the initial reboot failed, even after a couple of days attempt, but after a power cycle it worked. I'm puzzled by that behaviour. Is anyone here familar with the GPS25 family, dating from the turn of the millennium? As an aside, a Jupiter TU60 GPS module was also in use on site, delivering a GPS locked 10kHz signal. This I used to lock a 10MHz reference in "Probably the Simplest GPSDO Possible" http://g4jnt.com/SimpleGPSDO.pdf That module, which is not a lot newer than the Garmin, did appear to have survived the reboot as the resulting frequencies of the beacons were spot-on when they returned with their modulation faults. However, in the spirit of doing the job properly, it too is being replaced with a Leo-Bodnar mini GPSDO. All beacon details at scrbg.org Andy www.g4jnt.com _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there.