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: [email protected] > Date: Tue, 30 Dec 2014 09:33:06 -0500 > To: [email protected] > Subject: Re: [time-nuts] New GPSDO on EBAY From China > > Hi > > > On Dec 29, 2014, at 8:51 PM, Li Ang <[email protected]> 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 <[email protected]>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 <[email protected]> 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.XHJlQL&id=42336500072 > >>> > >>> > >>> > >>> > >>> 2014-12-29 1:56 GMT+08:00 Dan Rae <[email protected]>: > >>> > >>>> 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 -- [email protected] > >>>> To unsubscribe, go to https://www.febo.com/cgi-bin/ > >>>> mailman/listinfo/time-nuts > >>>> and follow the instructions there. > >>>> > >>> _______________________________________________ > >>> time-nuts mailing list -- [email protected] > >>> To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > >>> and follow the instructions there. > >> > >> _______________________________________________ > >> time-nuts mailing list -- [email protected] > >> 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 -- [email protected] > > To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
