Re: [time-nuts] Chinese GPSDOs
All three seam to be Chinese customer specific devices with focus on time. I bought three of the Trimble units we call them Tbolt 2 because of design similarities. On LH you will notice one thing like the original Tbolt it shows frequency jumps of 1 E -10 but also once every hour it does a major correction plus or minus. It is once an hour depending on when powered up. Frequency measurements confirm the excursions. The result is a maximum 1 pps excursion of plus minus 4 nsec. This is comparable to the Furuno GT87 and four times better than Tbolt 1. All tests are 24 hours against a very good HP 5065A, backed up with Cs. Bert Kehren In a message dated 4/17/2020 11:52:31 AM Eastern Standard Time, time-n...@welwarsky.de writes: On Freitag, 17. April 2020 16:04:15 CEST Steve - Home wrote: > There are some Chinese GPSDOs currently on eBay, containing a Symmetricom > 10MHz oscillator and a Furuno GT-8031 GPS receiver. Has anyone had any > experience with them? It’s hard to tell from the pictures what the power > requirements are. I know the GT-8031 is an older 8-channel receiver. I was > considering one for a portable 10MHz reference. Anyone checked these out > yet? I own three of them. One of them is the Symmetricom/Furuno combination you mentioned. Another one has a Samsung OXCO and a Ublox LEA-6T receiver. A third one is supposedly a Trimble OXCO, but I have no idea which GPS receiver it is using. It's the only one in an enclosure and I didn't bother yet to open it. They're all basically identical in form and structure. Same form factor, same inputs and outputs. I even bothered to make an adapter PCB with a switching regulator so that I can operate them more easily. They operate on 5.5V, taking in a little over 2A while the OCXO heats up. I have no equipment yet to assess their performance. Anyway they're all scrap telecom equipment, many of them are unchecked and damaged, with components missing (ripped off of the PCBs), cables cut. The OCXOs are genuine as far as I can tell but they all have undocumented service life and you don't know what they have been exposed to mechanically. If you plan to order one, I suggest to get one with an Ublox receiver. The Furuno is likely the oldest and weakest, it's also GPS-only. Afaict, the LEA-6T can at least receive GPS and GLONASS. From all three, I like the Samsung best, going by the performance I see when connecting it to "Lady Heather". The Symmetricom is the worst. Probably the OCXO has taken a hit. The Trimble is so-so. Of course there's a thread on the EEVblog forum dealing with all their variants: https://www.eevblog.com/forum/projects/a-look-at-my-symmetricom-gpsdo-(ocxo-furuno-receiver)/[1] HTH. BR, Matthias > > Steve > WB0DBS > > > > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow > the instructions there. [1] https://www.eevblog.com/forum/projects/a-look-at-my-symmetricom-gpsdo-(ocxo-furuno-receiver)/ ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Chinese GPSDOs
On Freitag, 17. April 2020 16:04:15 CEST Steve - Home wrote: > There are some Chinese GPSDOs currently on eBay, containing a Symmetricom > 10MHz oscillator and a Furuno GT-8031 GPS receiver. Has anyone had any > experience with them? It’s hard to tell from the pictures what the power > requirements are. I know the GT-8031 is an older 8-channel receiver. I was > considering one for a portable 10MHz reference. Anyone checked these out > yet? I own three of them. One of them is the Symmetricom/Furuno combination you mentioned. Another one has a Samsung OXCO and a Ublox LEA-6T receiver. A third one is supposedly a Trimble OXCO, but I have no idea which GPS receiver it is using. It's the only one in an enclosure and I didn't bother yet to open it. They're all basically identical in form and structure. Same form factor, same inputs and outputs. I even bothered to make an adapter PCB with a switching regulator so that I can operate them more easily. They operate on 5.5V, taking in a little over 2A while the OCXO heats up. I have no equipment yet to assess their performance. Anyway they're all scrap telecom equipment, many of them are unchecked and damaged, with components missing (ripped off of the PCBs), cables cut. The OCXOs are genuine as far as I can tell but they all have undocumented service life and you don't know what they have been exposed to mechanically. If you plan to order one, I suggest to get one with an Ublox receiver. The Furuno is likely the oldest and weakest, it's also GPS-only. Afaict, the LEA-6T can at least receive GPS and GLONASS. From all three, I like the Samsung best, going by the performance I see when connecting it to "Lady Heather". The Symmetricom is the worst. Probably the OCXO has taken a hit. The Trimble is so-so. Of course there's a thread on the EEVblog forum dealing with all their variants: https://www.eevblog.com/forum/projects/a-look-at-my-symmetricom-gpsdo-(ocxo-furuno-receiver)/[1] HTH. BR, Matthias > > Steve > WB0DBS > > > > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow > the instructions there. [1] https://www.eevblog.com/forum/projects/a-look-at-my-symmetricom-gpsdo-(ocxo-furuno-receiver)/ ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Chinese GPSDOs
Hi GPSDO’s come from China for a very simple reason: All the world’s scrap gear is sent to China for “reclamation”. It’s just another element in the great flow of material being recycled. For a variety of reasons China is the destination of choice for electronics scrap. Like it or not, telecom gear lives a pretty short life these days. It’s designed / sold / deployed and then 5 or 10 years later it’s replaced. When it’s pulled out, it likely goes in a container headed for China. The scrap out process on this stuff often is not pretty. If you head over to Mr Google, there are is a lot of information on just how it gets done. This is very much *not* the way you would want it done in your back yard. The net result is that we get sub assemblies out of this or that telecom system dirt cheap. They mostly are < 15 years old, so reasonably state of the art. If it’s showing up in quantities you can notice on eBay, it was built for one of the big OEM’s. The assemblies were built by somebody who very much does know what they are doing. Does this mean that a telecom GPSDO is the perfect answer to every need? Of course not. Somewhere there was a spec for this or that module. They met that spec when new. The performance required almost certainly focused on holdover. That is rarely a focus for a standard in a basement lab. The Trimble Thunderbolt is simply one of the many GPSDO’s that fit into this category. There were lots of GPSDO’s (some quite good) before the Tbolt. There have been many waves of parts since then. What is sure - when they are actively being reclaimed, the price will be low and the quantities high. In a few years, prices will climb …. Lots of fun Bob > On Apr 17, 2020, at 10:52 AM, Tobias Pluess wrote: > > I wonder why the only (or at least, most of the) GPSDOs one can find on > eBay are from China. Is there a reason for that? > I would like to buy used GPSDOs and OCXOs from other sources because the > stuff from China is often of doubtful pedigree and I would never 100% trust > one of those. They often look like they were treated very badly and I have > the impression that it is often unqualified personnel who pulls out the > GPSDOs from whatever equipment they have there. > The same is for Rb standards. I would already have one, but I can only find > Chinese sources, so I better keep my money than I buy a Rb standard from > which I don't know whether it was treated properly when removed from some > electronic equipment. > > Having said that I can add that I do have one of those dubious GPSDOs from > there; however not the particular model you mentioned. The GPSDO works but > I don't know whether it can be trusted. I once compared it to a Trimble > Thunderbolt, but I am not sure whether it was the Trimble which was > unstable or my own unit. It looks like the seller has made some > modifications to it and I don't know why. Also, there is no measurement > data available. > > > Tobias > HB9FSX > > > On Fri, Apr 17, 2020 at 4:05 PM Steve - Home wrote: > >> There are some Chinese GPSDOs currently on eBay, containing a Symmetricom >> 10MHz oscillator and a Furuno GT-8031 GPS receiver. Has anyone had any >> experience with them? It’s hard to tell from the pictures what the power >> requirements are. I know the GT-8031 is an older 8-channel receiver. I was >> considering one for a portable 10MHz reference. Anyone checked these out >> yet? >> >> Steve >> WB0DBS >> >> >> >> >> ___ >> time-nuts mailing list -- time-nuts@lists.febo.com >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. >> > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Chinese GPSDOs
Leo Bodnar (Great Britain) makes some nice GPSDO devices for reasonable prices, albeit TXCO. http://www.leobodnar.com/shop/index.php?main_page=product_info=107_id=234 On Fri, Apr 17, 2020 at 10:53 AM Tobias Pluess wrote: > I wonder why the only (or at least, most of the) GPSDOs one can find on > eBay are from China. Is there a reason for that? > I would like to buy used GPSDOs and OCXOs from other sources because the > stuff from China is often of doubtful pedigree and I would never 100% trust > one of those. They often look like they were treated very badly and I have > the impression that it is often unqualified personnel who pulls out the > GPSDOs from whatever equipment they have there. > The same is for Rb standards. I would already have one, but I can only find > Chinese sources, so I better keep my money than I buy a Rb standard from > which I don't know whether it was treated properly when removed from some > electronic equipment. > > Having said that I can add that I do have one of those dubious GPSDOs from > there; however not the particular model you mentioned. The GPSDO works but > I don't know whether it can be trusted. I once compared it to a Trimble > Thunderbolt, but I am not sure whether it was the Trimble which was > unstable or my own unit. It looks like the seller has made some > modifications to it and I don't know why. Also, there is no measurement > data available. > > > Tobias > HB9FSX > > > On Fri, Apr 17, 2020 at 4:05 PM Steve - Home wrote: > > > There are some Chinese GPSDOs currently on eBay, containing a Symmetricom > > 10MHz oscillator and a Furuno GT-8031 GPS receiver. Has anyone had any > > experience with them? It’s hard to tell from the pictures what the power > > requirements are. I know the GT-8031 is an older 8-channel receiver. I > was > > considering one for a portable 10MHz reference. Anyone checked these out > > yet? > > > > Steve > > WB0DBS > > > > > > > > > > ___ > > time-nuts mailing list -- time-nuts@lists.febo.com > > To unsubscribe, go to > > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > > and follow the instructions there. > > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Chinese GPSDOs
I wonder why the only (or at least, most of the) GPSDOs one can find on eBay are from China. Is there a reason for that? I would like to buy used GPSDOs and OCXOs from other sources because the stuff from China is often of doubtful pedigree and I would never 100% trust one of those. They often look like they were treated very badly and I have the impression that it is often unqualified personnel who pulls out the GPSDOs from whatever equipment they have there. The same is for Rb standards. I would already have one, but I can only find Chinese sources, so I better keep my money than I buy a Rb standard from which I don't know whether it was treated properly when removed from some electronic equipment. Having said that I can add that I do have one of those dubious GPSDOs from there; however not the particular model you mentioned. The GPSDO works but I don't know whether it can be trusted. I once compared it to a Trimble Thunderbolt, but I am not sure whether it was the Trimble which was unstable or my own unit. It looks like the seller has made some modifications to it and I don't know why. Also, there is no measurement data available. Tobias HB9FSX On Fri, Apr 17, 2020 at 4:05 PM Steve - Home wrote: > There are some Chinese GPSDOs currently on eBay, containing a Symmetricom > 10MHz oscillator and a Furuno GT-8031 GPS receiver. Has anyone had any > experience with them? It’s hard to tell from the pictures what the power > requirements are. I know the GT-8031 is an older 8-channel receiver. I was > considering one for a portable 10MHz reference. Anyone checked these out > yet? > > Steve > WB0DBS > > > > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
[time-nuts] Chinese GPSDOs
There are some Chinese GPSDOs currently on eBay, containing a Symmetricom 10MHz oscillator and a Furuno GT-8031 GPS receiver. Has anyone had any experience with them? It’s hard to tell from the pictures what the power requirements are. I know the GT-8031 is an older 8-channel receiver. I was considering one for a portable 10MHz reference. Anyone checked these out yet? Steve WB0DBS ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
