[time-nuts] New GPSDO on EBAY From China

Bob Camp kb8tq at n1k.org
Mon Dec 29 16:54:09 EST 2014


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. 

> On Dec 29, 2014, at 2:07 PM, xaos <xaos at 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.
> 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 at 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 at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.

More information about the time-nuts mailing list