Andy So funny. I had some of these old gps units. Like you they sort of died over time. I have to say taking the plastic top off was difficult. Never discovered what was up. But I did the same as you. The cheap and cheerful NEO-6. That was the end of any issue. Regards Paul WB8TSL
On Wed, Feb 9, 2022 at 9:23 AM Andy Talbot <[email protected]> wrote: > 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 -- [email protected] -- To unsubscribe send > an email to [email protected] > To unsubscribe, go to and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] -- To unsubscribe send an email to [email protected] To unsubscribe, go to and follow the instructions there.
