[time-nuts] New GPSDO on EBAY From China

xaos xaos at darksmile.net
Mon Dec 29 14:07:26 EST 2014

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
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