[time-nuts] Re: HP Z3801A - Dead GPS Receiver - Oncore VP
Hi The stability profile of the GPS timing signal changed significantly when SA was turned off. Things like sawtooth correction that didn’t make much difference in the 1990’s now did make a difference. Time constants and OCXO parameters that made sense “before” didn’t make sense “after”. More or less: When you make profound changes in the GPS timing signal, the best approach to accurately recovering that signal has to change to match the new signal. Does everybody change everything the next day? Of course not. It takes a while for folks to work out what’s what with the “new rules”. Bob > On Oct 14, 2021, at 8:12 PM, Hal Murray wrote: > > > kb...@n1k.org said: >> The other way to look at it: The Z3801 and it???s kin basically went obsolete >> in 2000 when SA was turned off. Once that happened, the design approach >> changed. > > Could you please say more. What changed in the design approach? > > Can I tell the difference by looking at a box? Or poking at the serial port? > > > > -- > These are my opinions. I hate spam. > > > ___ > 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. ___ 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.
[time-nuts] Re: HP Z3801A - Dead GPS Receiver - Oncore VP
kb...@n1k.org said: > The other way to look at it: The Z3801 and it???s kin basically went obsolete > in 2000 when SA was turned off. Once that happened, the design approach > changed. Could you please say more. What changed in the design approach? Can I tell the difference by looking at a box? Or poking at the serial port? -- These are my opinions. I hate spam. ___ 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.
[time-nuts] Re: HP Z3801A - Dead GPS Receiver - Oncore VP
Hi The other way to look at it: The Z3801 and it’s kin basically went obsolete in 2000 when SA was turned off. Once that happened, the design approach changed. That, on top of whatever system life cycle issues applied pushed it onto the scrap heap. No, that’s not to say you should toss out your 3801’s. Only that it was no longer competitive for new designs. Bob > On Oct 14, 2021, at 6:48 PM, Magnus Danielson via time-nuts > wrote: > > Hi, > > It kind of depends. The Z3801A was really crafted to meet the needs of CDMA > mobile stations. That had it's life-span. Other GPSDOs can sit for very long > time and when they fail, much around them can have changed, or mostly things > have been added. > > It used to be that GPSes could be installed and no real intention to upgrade > existed. Some where even questionable if they could be upgraded during their > lifetime, where as others could maybe be upgraded in the field or at least > required the vendors service organisation being involved. Others was dead > easy to upgrade in the field by the user. Very few firms still support their > oldest devices, but it seems to be mostly because they can and they like the > challenge. For some reason, being able to upgrade it in the field, remotely > in secure way and still have support enough to do it has creeped into > requirements. I helped to push that. DHS published it and we just started an > IEEE standard for it. Little bit of a side-track, but never the less. > Awareness have increased. > > Cheers, > Magnus > > On 2021-10-12 18:58, Bob kb8tq wrote: >> Hi >> >> If a cell tower is running for 5 years without an upgrade, that’s doing >> pretty well. >> Ten years is an eternity in this case. Even for core network stuff, the >> “expected >> lifetime” in the spec rarely makes it to 20 years and pretty much never goes >> past >> that (in the spec.). Does the stuff last longer? In some cases it most >> certainly does. >> Is the firmware still supported after X years? ….. h…. >> >> One way to “see” this is to take a look at the date codes on this gear as it >> shows >> up on eBay. The 3801’s headed out into the field in the late 90’s and became >> a >> “thing” for Time Nuts to buy and poke at by the early 2000’s. >> >> How you factor in the delay between being pulled out of service in who knows >> where, auctioned off, shipped to China, parted out, parts resold, and listed >> on eBay is >> unclear. I’d bet they go by slow boat heading over there …. >> >> Bob >> >>> On Oct 12, 2021, at 12:27 PM, Hal Murray >>> wrote: >>> >>> >>> kb...@n1k.org said: I???ve run 3801???s for years and years without ever power cycling them. Other than power supply failure, they never had a problem. They did get detailed monitoring pretty much all the time. >>> I was guessing that the reboot-every-few-months recipe was trying to dance >>> around the week number roll over issue. >>> >>> Has anybody figured out where/when it writes whatever it needs so that it >>> comes up right on power up? >>> >>> On the initial application (cell towers?), was there any expectation of >>> lifetime? In particular were they expected to keep going over WNRO and/or >>> was >>> there a difference between run over WNRO and spares sitting on the shelf >>> coming up after WNRO? >>> >>> -- >>> These are my opinions. I hate spam. >>> >>> >>> ___ >>> 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. >> ___ >> 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. > ___ > 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. ___ 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.
[time-nuts] Re: HP Z3801A - Dead GPS Receiver - Oncore VP
Hi, It kind of depends. The Z3801A was really crafted to meet the needs of CDMA mobile stations. That had it's life-span. Other GPSDOs can sit for very long time and when they fail, much around them can have changed, or mostly things have been added. It used to be that GPSes could be installed and no real intention to upgrade existed. Some where even questionable if they could be upgraded during their lifetime, where as others could maybe be upgraded in the field or at least required the vendors service organisation being involved. Others was dead easy to upgrade in the field by the user. Very few firms still support their oldest devices, but it seems to be mostly because they can and they like the challenge. For some reason, being able to upgrade it in the field, remotely in secure way and still have support enough to do it has creeped into requirements. I helped to push that. DHS published it and we just started an IEEE standard for it. Little bit of a side-track, but never the less. Awareness have increased. Cheers, Magnus On 2021-10-12 18:58, Bob kb8tq wrote: Hi If a cell tower is running for 5 years without an upgrade, that’s doing pretty well. Ten years is an eternity in this case. Even for core network stuff, the “expected lifetime” in the spec rarely makes it to 20 years and pretty much never goes past that (in the spec.). Does the stuff last longer? In some cases it most certainly does. Is the firmware still supported after X years? ….. h…. One way to “see” this is to take a look at the date codes on this gear as it shows up on eBay. The 3801’s headed out into the field in the late 90’s and became a “thing” for Time Nuts to buy and poke at by the early 2000’s. How you factor in the delay between being pulled out of service in who knows where, auctioned off, shipped to China, parted out, parts resold, and listed on eBay is unclear. I’d bet they go by slow boat heading over there …. Bob On Oct 12, 2021, at 12:27 PM, Hal Murray wrote: kb...@n1k.org said: I???ve run 3801???s for years and years without ever power cycling them. Other than power supply failure, they never had a problem. They did get detailed monitoring pretty much all the time. I was guessing that the reboot-every-few-months recipe was trying to dance around the week number roll over issue. Has anybody figured out where/when it writes whatever it needs so that it comes up right on power up? On the initial application (cell towers?), was there any expectation of lifetime? In particular were they expected to keep going over WNRO and/or was there a difference between run over WNRO and spares sitting on the shelf coming up after WNRO? -- These are my opinions. I hate spam. ___ 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. ___ 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. ___ 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.
