[time-nuts] New GPSDO on EBAY From China
csteinmetz at yandex.com
Sun Dec 28 18:11:22 EST 2014
>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%
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.
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