Hi all, There was some consternation here 5 months ago when Z3815A GPSDOs began reporting a date 1024 weeks in the past. This was due to a storage overflow condition in the Furuno GPS receiver in the Z3915A. The designers probably never anticipated that they would still be in use 20 years later.... Oscillator discipline was unaffected as the 1 pps was still good.
Obsessional types like me looked for a solution. There didn't seem to be any knowledge out there about reprogramming the receivers so it had to be a transplant. Furuno GT-8031 timing receivers are available on ebay and not prohibitively expensive. They are about half the size of a matchbox and work at 3.3V TTL levels. The interface connector is a 2mm pitch 2X5 pin header and the antenna connection is a pigtail with a Hirose u.fl connector. The interface is 9600,n,8,1. I picked one up a few months ago and it took a while to get the appropriate connectors etc but I eventually found enough time to make a little interface PCB compete with a Li button cell backup battery. I lashed it up tonight into the Z3815A and it works!!! The GPS locks the oscillator and the Z3815A reports the correct time & date. As I write this it's been going for an hour or so and the survey is not complete, the Z3815A still reporting reduced accuracy. It is showing an antenna alarm for some reason so the yellow "operation" alarm LED is lit. That may be because I'm powering the receiver externally at the moment and there would be no current being drawn from the Z3815A 5 volt supply. I'll work on that in the morning. The interface board draws a total of about 100 mA including the antenna current and I'm hoping that won't be high enough to give an antenna alarm in the other direction. If so I'll have to change the 3.3 volt supply from being zener stabilized to being series voltage dropped. More news as it breaks!! Morris _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.