Re: [time-nuts] New GPSDO on EBAY From China
Hi Based on the dates I’ve seen on pictures and boards, this is a *very* new project. I suspect that what we are looking at is approximately beta test software. There’s likely to be a good part of a year or more spent optimizing the code. There’s no shame in any of that. It’s the nature of doing this kind of thing. You need working hardware to refine the software. To the points made earlier, the designer(s) have avoided many of the traps people fall into when doing this kind of thing. They are off to a good start. Where they end up will depend a lot on how many people are involved and what sort of gear they all have for measuring things. Could this be the final hardware? Maybe. Could they find a hardware issue when debugging the software? That stuff happens (to me). Could all our yelling about this turn them off to the idea and the whole project crashes and burns - I’ve seen that before as well. At this point we know little of the hardware design. Since we also know virtually noting about the internal Chinese market for parts, I doubt we could help much if we did see a bill of material. Some of this is simply a matter of trust in the designer. That’s not a bad thing. I’d much rather see a $75 design that works with parts they can get than a $800 design done with US parts. Hopefully we will find out more about this project as it moves forward. It’s only going to get better from here on. Does any of that change what I would recommend for a “one and only” GPSDO today? No. If it’s going to be your only standard, you want something that’s had the bugs worked out of it. The recommendation stands *not* because the Chinese GPSDO is in some way defective or a bad idea. It stands simply because you should play it safe on a single standard. - Right now there are several GPSDO’s on the market in the $150 to $250 (delivered) price range. That also is a good thing. You have multiple choices and there is no need for a “one size fits all” answer. Bob On Dec 29, 2014, at 2:07 PM, xaos x...@darksmile.net wrote: You have to give the guy credit for trying. What is a shame here is that he did not publish the schematics and the source code. If anyone knows him he should just ask him. We tend to be sceptics here but that's the nature of the game. However, I don't want anyone to think that we are elitist. I remember my first GPSDO, by Brooks Sherra, on QST. I remember reading the schematic and the source code many times until I got it. It is the reason I got interested in time-nuts to begin with. So, I think we would all benefit from going a bit deeper on this new unit. I hope the designer is reading this. GKH, N2FGX On 12/29/2014 12:50 AM, Charles Steinmetz wrote: Li Ang wrote: This unit is done by BG7TBL. In his store on taobao.com, there is a adev chart. Please refrer to this link That ADEV chart (see below) raises more questions than it answers. At least the time constant is not too short (a very common problem with DIY GPSDOs). But when the GPS takes over above the crossover (tau ~ 5000 seconds), the ADEV is ~2e-11. GPS should be significantly better than this at 5000 seconds. It appears that something is wrong with the design. Best regards, Charles ___ 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. ___ 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. ___ 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.
Re: [time-nuts] New GPSDO on EBAY From China
Hi One of my friend had one. Here is the test result from him. Bob Camp kb...@n1k.org于2014年12月29日星期一写道： Hi Ok, well that’s a move forward on this GPSDO. There is a *lot* more data on that listing than there was a month ago. Thanks for digging it up and posting the link. If you look at the ADEV at 1 second, it’s running at 2.67 x10^-11. That’s all coming from the Erratum Rb that they are using as a reference. At 100 seconds the Rb should be around 2.67 x10^-12 and the MV-89 should be about 2x10^-11. They combine as the square root, so that would be 3.3 ppt or less. The unit is running at 4.8 ppt so the filter is having some impact at that point. Out around 5,000 seconds the unit has a major hump. The Nortel GPSTM has a similar hump, but much closer in. It’s performance at 5K seconds is much better. The Lucent KS boxes beat this part across the entire range. That makes some assumptions, since there is no good ADEV data inside 100 seconds on the plot. The final question about the plot would be - what happens at longer tau? The run was stopped before it really got past the peak in the filter. It would be nice to see some data that at least gets back down to 1 ppt at the longer tau’s. Without that data it’s unclear how well the whole system is doing. That’s not to say it’s not doing well. It could be doing a great job, there’s just no way to know from the data. My guess is that this is very much like your counter project, just a bit further along. They have a nice looking unit, but are still trying to figure out the bugs and finish up the software … Bob On Dec 28, 2014, at 6:19 PM, Li Ang lll...@gmail.com wrote: Hi This unit is done by BG7TBL. In his store on taobao.com, there is a adev chart. Please refrer to this link http://item.taobao.com/item.htm?spm=a1z10.3.w4002-1278071728.49.XHJlQLid=42336500072 2014-12-29 1:56 GMT+08:00 Dan Rae dan...@verizon.net: On 12/28/2014 7:25 AM, David Smith wrote: Hello Friends, I found this new inexpensive GPSDO on ebay listed from a seller from China: Dave, these have been discussed in the past at some length on this list. I would point out that they use a re-cycled Morion OCXO. I have had two of these ovens from China; one worked fine, the other has a very high level of spurious outputs. I would be wary of using these in anything without first testing them thoroughly. Dan ___ 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. ___ 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. ___ 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. ___ 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.
Re: [time-nuts] New GPSDO on EBAY From China
Hi On Dec 29, 2014, at 8:51 PM, Li Ang lll...@gmail.com wrote: Hi One of my friend had one. Here is the test result from him. Ok, that data is actually more encouraging than the data on the selling site. He ran it long enough to get past the hump in the ADEV curve at 4,000 seconds. The blue trace shows that the test setup *can* resolve the data properly. So now the question becomes - what is going on with the filter software in the BG7TBL unit? It’s obviously done differently than the HP filter software. There are a number of people (not me) on the list that have expressed interest in digging into GPSDO firmware. Bob Bob Camp kb...@n1k.org于2014年12月29日星期一写道： Hi Ok, well that’s a move forward on this GPSDO. There is a *lot* more data on that listing than there was a month ago. Thanks for digging it up and posting the link. If you look at the ADEV at 1 second, it’s running at 2.67 x10^-11. That’s all coming from the Erratum Rb that they are using as a reference. At 100 seconds the Rb should be around 2.67 x10^-12 and the MV-89 should be about 2x10^-11. They combine as the square root, so that would be 3.3 ppt or less. The unit is running at 4.8 ppt so the filter is having some impact at that point. Out around 5,000 seconds the unit has a major hump. The Nortel GPSTM has a similar hump, but much closer in. It’s performance at 5K seconds is much better. The Lucent KS boxes beat this part across the entire range. That makes some assumptions, since there is no good ADEV data inside 100 seconds on the plot. The final question about the plot would be - what happens at longer tau? The run was stopped before it really got past the peak in the filter. It would be nice to see some data that at least gets back down to 1 ppt at the longer tau’s. Without that data it’s unclear how well the whole system is doing. That’s not to say it’s not doing well. It could be doing a great job, there’s just no way to know from the data. My guess is that this is very much like your counter project, just a bit further along. They have a nice looking unit, but are still trying to figure out the bugs and finish up the software … Bob On Dec 28, 2014, at 6:19 PM, Li Ang lll...@gmail.com wrote: Hi This unit is done by BG7TBL. In his store on taobao.com, there is a adev chart. Please refrer to this link http://item.taobao.com/item.htm?spm=a1z10.3.w4002-1278071728.49.XHJlQLid=42336500072 2014-12-29 1:56 GMT+08:00 Dan Rae dan...@verizon.net: On 12/28/2014 7:25 AM, David Smith wrote: Hello Friends, I found this new inexpensive GPSDO on ebay listed from a seller from China: Dave, these have been discussed in the past at some length on this list. I would point out that they use a re-cycled Morion OCXO. I have had two of these ovens from China; one worked fine, the other has a very high level of spurious outputs. I would be wary of using these in anything without first testing them thoroughly. Dan ___ 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. ___ 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. ___ 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. 86068848562b6ac3c8c48d76d.jpg___ 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. ___ 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.
Re: [time-nuts] New GPSDO on EBAY From China
Thanks for the discussion on this GPSDO. I researched the archives on this going back a few months but didn't find anything. Although I consider myself a newby or novice Time-Nut I do have three other GPSDO's I've had a Z3801 running for more than 10 years. My interest in the unit in question lies in the need for a light weight unit I can use as a stable accurate source for my 24 GHz transverter that I use for my rover and contesting efforts. I need something light weight as well as accurate and stable with low phase noise and needs to be able to be located on or close to a portable tripod. I did order one of James Millers units to fulfill these needs. I just thought this may be a much less expensive alternative. Thanks again for the discussion. Happy New Year to all! Dave - W6TE From: kb...@n1k.org Date: Tue, 30 Dec 2014 09:33:06 -0500 To: time-nuts@febo.com Subject: Re: [time-nuts] New GPSDO on EBAY From China Hi On Dec 29, 2014, at 8:51 PM, Li Ang lll...@gmail.com wrote: Hi One of my friend had one. Here is the test result from him. Ok, that data is actually more encouraging than the data on the selling site. He ran it long enough to get past the hump in the ADEV curve at 4,000 seconds. The blue trace shows that the test setup *can* resolve the data properly. So now the question becomes - what is going on with the filter software in the BG7TBL unit? It’s obviously done differently than the HP filter software. There are a number of people (not me) on the list that have expressed interest in digging into GPSDO firmware. Bob Bob Camp kb...@n1k.org于2014年12月29日星期一写道： Hi Ok, well that’s a move forward on this GPSDO. There is a *lot* more data on that listing than there was a month ago. Thanks for digging it up and posting the link. If you look at the ADEV at 1 second, it’s running at 2.67 x10^-11. That’s all coming from the Erratum Rb that they are using as a reference. At 100 seconds the Rb should be around 2.67 x10^-12 and the MV-89 should be about 2x10^-11. They combine as the square root, so that would be 3.3 ppt or less. The unit is running at 4.8 ppt so the filter is having some impact at that point. Out around 5,000 seconds the unit has a major hump. The Nortel GPSTM has a similar hump, but much closer in. It’s performance at 5K seconds is much better. The Lucent KS boxes beat this part across the entire range. That makes some assumptions, since there is no good ADEV data inside 100 seconds on the plot. The final question about the plot would be - what happens at longer tau? The run was stopped before it really got past the peak in the filter. It would be nice to see some data that at least gets back down to 1 ppt at the longer tau’s. Without that data it’s unclear how well the whole system is doing. That’s not to say it’s not doing well. It could be doing a great job, there’s just no way to know from the data. My guess is that this is very much like your counter project, just a bit further along. They have a nice looking unit, but are still trying to figure out the bugs and finish up the software … Bob On Dec 28, 2014, at 6:19 PM, Li Ang lll...@gmail.com wrote: Hi This unit is done by BG7TBL. In his store on taobao.com, there is a adev chart. Please refrer to this link http://item.taobao.com/item.htm?spm=a1z10.3.w4002-1278071728.49.XHJlQLid=42336500072 2014-12-29 1:56 GMT+08:00 Dan Rae dan...@verizon.net: On 12/28/2014 7:25 AM, David Smith wrote: Hello Friends, I found this new inexpensive GPSDO on ebay listed from a seller from China: Dave, these have been discussed in the past at some length on this list. I would point out that they use a re-cycled Morion OCXO. I have had two of these ovens from China; one worked fine, the other has a very high level of spurious outputs. I would be wary of using these in anything without first testing them thoroughly. Dan ___ 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. ___ 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. ___ 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. 86068848562b6ac3c8c48d76d.jpg___ 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
Re: [time-nuts] New GPSDO on EBAY From China
Li Ang wrote: This unit is done by BG7TBL. In his store on taobao.com, there is a adev chart. Please refrer to this link That ADEV chart (see below) raises more questions than it answers. At least the time constant is not too short (a very common problem with DIY GPSDOs). But when the GPS takes over above the crossover (tau ~ 5000 seconds), the ADEV is ~2e-11. GPS should be significantly better than this at 5000 seconds. It appears that something is wrong with the design. Best regards, Charles ___ 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.
Re: [time-nuts] New GPSDO on EBAY From China
I remember seeing this same unit here on this list some weeks ago. As I remember it is built from some plans that were published. You can see that it uses a surplus OCXO. The seller is good to claim the specs of his GPSDO as being two orders of magnitude above the OCXO. because we don't know what surplus OCXO this unit will be shipped with. If you just want a low cost GPSDO you can build one for maybe $50 total and then it is repairable and should last forever. If you want predictable performance you'll have to buy a name brand commercial unit. This Chinese built unit looks to be aimed at someone who needs a lab bench reference to keep his frequency counter on calibration and does not want to do any soldering. On Sun, Dec 28, 2014 at 7:25 AM, David Smith w...@msn.com wrote: Hello Friends, I found this new inexpensive GPSDO on ebay listed from a seller from China: http://www.ebay.com/itm/GPS-DISCPLINED-CLOCK-GPSDO-10M-OUTPUT-SQUARE-WAVE-/111514491254?pt=LH_DefaultDomain_0hash=item19f6c81976 It looks interesting and tempting BUT the seller doesn't give any spec's on the unit or osc type. The seller has 10 negative and 18 neutral feedback's in the past 6 months out of a total of 2110 for a feedback score of 99.6%; many for poor communication. Does anyone on the list have any experience with this GPSDO? Any advice on buying one? Best regards and Happy New Year! Dave - W6TE ___ 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. -- Chris Albertson Redondo Beach, California ___ 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.
Re: [time-nuts] New GPSDO on EBAY From China
The OCXO is a Morion (Russia) MV89A. You may download a datasheet from http://www.morion.com.ru/catalog_pdf/MV89-OCXO.pdf Looks decent, stability vs. temperature and aging are as usual. BG7TBL is a Chinese radioamateur, quite known for his designs. 73 - Marco IK1ODO ___ 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.
Re: [time-nuts] New GPSDO on EBAY From China
Hi Ok, well that’s a move forward on this GPSDO. There is a *lot* more data on that listing than there was a month ago. Thanks for digging it up and posting the link. If you look at the ADEV at 1 second, it’s running at 2.67 x10^-11. That’s all coming from the Erratum Rb that they are using as a reference. At 100 seconds the Rb should be around 2.67 x10^-12 and the MV-89 should be about 2x10^-11. They combine as the square root, so that would be 3.3 ppt or less. The unit is running at 4.8 ppt so the filter is having some impact at that point. Out around 5,000 seconds the unit has a major hump. The Nortel GPSTM has a similar hump, but much closer in. It’s performance at 5K seconds is much better. The Lucent KS boxes beat this part across the entire range. That makes some assumptions, since there is no good ADEV data inside 100 seconds on the plot. The final question about the plot would be - what happens at longer tau? The run was stopped before it really got past the peak in the filter. It would be nice to see some data that at least gets back down to 1 ppt at the longer tau’s. Without that data it’s unclear how well the whole system is doing. That’s not to say it’s not doing well. It could be doing a great job, there’s just no way to know from the data. My guess is that this is very much like your counter project, just a bit further along. They have a nice looking unit, but are still trying to figure out the bugs and finish up the software … Bob On Dec 28, 2014, at 6:19 PM, Li Ang lll...@gmail.com wrote: Hi This unit is done by BG7TBL. In his store on taobao.com, there is a adev chart. Please refrer to this link http://item.taobao.com/item.htm?spm=a1z10.3.w4002-1278071728.49.XHJlQLid=42336500072 2014-12-29 1:56 GMT+08:00 Dan Rae dan...@verizon.net: On 12/28/2014 7:25 AM, David Smith wrote: Hello Friends, I found this new inexpensive GPSDO on ebay listed from a seller from China: Dave, these have been discussed in the past at some length on this list. I would point out that they use a re-cycled Morion OCXO. I have had two of these ovens from China; one worked fine, the other has a very high level of spurious outputs. I would be wary of using these in anything without first testing them thoroughly. Dan ___ 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. ___ 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. ___ 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.
Re: [time-nuts] New GPSDO on EBAY From China
You have to give the guy credit for trying. What is a shame here is that he did not publish the schematics and the source code. If anyone knows him he should just ask him. We tend to be sceptics here but that's the nature of the game. However, I don't want anyone to think that we are elitist. I remember my first GPSDO, by Brooks Sherra, on QST. I remember reading the schematic and the source code many times until I got it. It is the reason I got interested in time-nuts to begin with. So, I think we would all benefit from going a bit deeper on this new unit. I hope the designer is reading this. GKH, N2FGX On 12/29/2014 12:50 AM, Charles Steinmetz wrote: Li Ang wrote: This unit is done by BG7TBL. In his store on taobao.com, there is a adev chart. Please refrer to this link That ADEV chart (see below) raises more questions than it answers. At least the time constant is not too short (a very common problem with DIY GPSDOs). But when the GPS takes over above the crossover (tau ~ 5000 seconds), the ADEV is ~2e-11. GPS should be significantly better than this at 5000 seconds. It appears that something is wrong with the design. Best regards, Charles ___ 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. ___ 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.
[time-nuts] New GPSDO on EBAY From China
Hello Friends, I found this new inexpensive GPSDO on ebay listed from a seller from China: http://www.ebay.com/itm/GPS-DISCPLINED-CLOCK-GPSDO-10M-OUTPUT-SQUARE-WAVE-/111514491254?pt=LH_DefaultDomain_0hash=item19f6c81976 It looks interesting and tempting BUT the seller doesn't give any spec's on the unit or osc type. The seller has 10 negative and 18 neutral feedback's in the past 6 months out of a total of 2110 for a feedback score of 99.6%; many for poor communication. Does anyone on the list have any experience with this GPSDO? Any advice on buying one? Best regards and Happy New Year! Dave - W6TE ___ 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.
Re: [time-nuts] New GPSDO on EBAY From China
Hi Dave, Bite the bullet and spring for the Lucent pair on Ebay - $150 , new, and the pair work fine. Lots of info on the list about them. 73, Bill, WA2DVU Cape May -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of David Smith Sent: Sunday, December 28, 2014 10:25 AM To: time-nuts@febo.com Subject: [time-nuts] New GPSDO on EBAY From China Hello Friends, I found this new inexpensive GPSDO on ebay listed from a seller from China: http://www.ebay.com/itm/GPS-DISCPLINED-CLOCK-GPSDO-10M-OUTPUT-SQUARE-WAVE-/1 11514491254?pt=LH_DefaultDomain_0hash=item19f6c81976 Dave - W6TE ___ 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. --- This email has been checked for viruses by Avast antivirus software. http://www.avast.com ___ 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.
Re: [time-nuts] New GPSDO on EBAY From China
On 12/28/2014 7:25 AM, David Smith wrote: Hello Friends, I found this new inexpensive GPSDO on ebay listed from a seller from China: Dave, these have been discussed in the past at some length on this list. I would point out that they use a re-cycled Morion OCXO. I have had two of these ovens from China; one worked fine, the other has a very high level of spurious outputs. I would be wary of using these in anything without first testing them thoroughly. Dan ___ 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.
Re: [time-nuts] New GPSDO on EBAY From China
Hi This unit is done by BG7TBL. In his store on taobao.com, there is a adev chart. Please refrer to this link http://item.taobao.com/item.htm?spm=a1z10.3.w4002-1278071728.49.XHJlQLid=42336500072 2014-12-29 1:56 GMT+08:00 Dan Rae dan...@verizon.net: On 12/28/2014 7:25 AM, David Smith wrote: Hello Friends, I found this new inexpensive GPSDO on ebay listed from a seller from China: Dave, these have been discussed in the past at some length on this list. I would point out that they use a re-cycled Morion OCXO. I have had two of these ovens from China; one worked fine, the other has a very high level of spurious outputs. I would be wary of using these in anything without first testing them thoroughly. Dan ___ 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. ___ 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.
Re: [time-nuts] New GPSDO on EBAY From China
Hi Quick summary if you don’t want to go back a month or two in the archives: 1) They appear to be a club project done by a ham club in China. 2) There are multiple versions in the pictures, some with more jumpers, some with fewer jumpers. 3) The design appears to be pretty new. Dates are all quite recent. 4) If English language doc’s or schematics exist on the part, nobody has been able to find them. To the extent translation software will let one look around, the same is true of Chinese doc’s. 5) If they interface to any sort of software, that information (and software) also seems to be among the “missing bits”. 6) They appear to be one off hand built units made from parts commonly available in the local Chinese market. The OCXO may (or may not) be the only suspect part on the unit you get. Simply put - we don’t really know anything at all about them. There is more information on things like the LTE Lite and the KS boxes. Both are in a similar price league to the Chinese box. That brings up the basic question of - why risk your money? The may be fine units. The doc’s might be out there. Until the doc’s show up and a seller posts some data, I’d stay away. If it’s your 20th GPSDO and you already have a couple of LTE’s and a couple pairs of KS’s - go for it. I would not make it my first GPSDO. Bob On Dec 28, 2014, at 12:56 PM, Dan Rae dan...@verizon.net wrote: On 12/28/2014 7:25 AM, David Smith wrote: Hello Friends, I found this new inexpensive GPSDO on ebay listed from a seller from China: Dave, these have been discussed in the past at some length on this list. I would point out that they use a re-cycled Morion OCXO. I have had two of these ovens from China; one worked fine, the other has a very high level of spurious outputs. I would be wary of using these in anything without first testing them thoroughly. Dan ___ 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. ___ 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.
Re: [time-nuts] New GPSDO on EBAY From China
Dave wrote: I found this new inexpensive GPSDO on ebay listed from a seller from China: It looks interesting and tempting BUT the seller doesn't give any spec's on the unit or osc type. The seller has 10 negative and 18 neutral feedback's in the past 6 months out of a total of 2110 for a feedback score of 99.6%; many for poor communication. Does anyone on the list have any experience with this GPSDO? Any advice on buying one? The photo looks like the whole main board was soldered by hand rather than by reflow. So, they appear to be onsie-twosies, not manufactured products. The probability of assembly errors goes way up for hand-assembled items. As Dan already pointed out, it uses a recycled Morion OCXO, and the failure rate of surplus Morion OCXOs is quite high. There is also no information about the PLL loop, and with a DIY circuit the presumption always has to be that it is not well designed (until the presumption is rebutted by measurement data -- and in this case, there is none). Finally, because of the way that ebay seller ratings work in practice, anything below 99.9% is a RISKY feedback score, IMO. Particularly if something is coming from so far away that it is hard or costly to return, I wouldn't buy from a vendor with a 99.6% feedback score. Could it be that the seller carefully QC's the Morions and they are all good? Could it be that he knows how to design a good long-TC all-digital PLL? Yes, both are possible. But until someone independent and with stature and a track record in such matters (tvb, Ackermann, and/or Miles) tests a few and posts the results, the presumption is against both propositions. Best regards, Charles ___ 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.
