Richard wrote:

It is very hard to say exactly what you will get, because the seller
(who uses a dozen or more different ebay IDs) seems to change the design
every time the wind shifts.  But typically they are FLLs (frequency
locked loops), not genuine PLLs (phase locked loops), and have a small
frequency offset because the design does not address some systemic
issues of FLL design.  It is unlikely to deliver better than 10e-11
performance with any certainty.

In addition to that, if  "Ex-ref from trimble thunderbolt GPSDO" is
supposed to make a buyer think it will have the best Trimble OCXO (P/N
37265), the one that was in the Trimble Thunderbolts of list legend,
that is almost certainly false.  It may have a Trimble-branded OCXO, but
even if it does it will be one of the many lesser part numbers.

To me, the attempts to mislead buyers is enough, by itself,  to rule out
dealing with that seller, under any of his ebay IDs.

Best regards,

Charles

"Full tested by Agilent 53132A with US-012 option and Ex-ref from
trimble thunderbolt
GPSDO."

I think what the seller saying is that the counter was externally
referenced to the Thunderbolt for the frequency measurements that they
state.

Cheers
Michael

On Sun, Jul 10, 2016 at 10:58 AM, Charles Steinmetz
csteinmetz@yandex.com wrote:

since you asked ...
Many thoughts, none of them good.
Recycled components sold for real money.
Too many "versions" to figure out "what you got".
If all you want is a frequency standard to turn it on and "forget it"
spend a few extra bucks and get one with all new components from a
domestic company.
Or if you want to have some fun put together one of your own.

At 04:40 PM 7/9/2016, Richard Mogford wrote:

Michael wrote:

Yes, on re-reading the listing, I believe you are right.  Thanks!

Charles

And when you build your own, you're still left with the issue of the oscillator.  In my experience, only about 2 out of 3 of the 34310-Ts I get from China are worth using.  If you buy them one at a time your odds aren't good.  OTOH, as your first oscillator, especially for HF use, noise and stability aren't quite as important as if you're multiplying up to microwaves.

But, as a starter GPSDO, probably anything is good.  Frequency accuracy, even if a fraction of a Hz off, is all you're looking for at first.  I bought one of Bert Zauhar's (VE2ZAZ) circuit boards and chips for my first one.  It was a good experience.  And when I was done, I had a GPSDO that was as good as most of what you find on ebay in the bargain basement, but at a much lower cost.  But then you need a case, and something to compare it to, and something even better, and then you're a time-nut.

But one thing to remember Richard, is that the time-nuts idea of accuracy is much different from what you may be used to.  For HF ham use,+/- 1Hz accuracy is a big deal.  In the time nuts community, phase accuracy to the nanosecond level (and even better, if possible!) is what's important.

Bob
 -----------------------------------------------------------------
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: Dimitri.p <dimitri@dotp.com>

To: Discussion of precise time and frequency measurement time-nuts@febo.com; time-nuts@febo.com
Sent: Saturday, July 9, 2016 9:14 PM
Subject: Re: [time-nuts] Good GPSDO on eBay?

since you asked ...
Many thoughts, none of them good.
Recycled components sold for real money.
Too many "versions" to figure out "what you got".
If all you want is a frequency standard to turn it on and "forget it"
spend a few extra bucks and get one with all new components from a
domestic company.
Or if you want to have some fun put together one of your own.

At 04:40 PM 7/9/2016, Richard Mogford wrote:

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.

To paraphrase a few other folks, taking on the task of building your own, even using the VE2ZAZ board as a basis is a very educational experience. It will teach you an enormous amount. There are lessons in control systems, phase and frequency locked loops, oven controllers, phase and frequency measurement, and doubtless lots of things I've overlooked.

Well worth the effort.

On Sat, Jul 9, 2016 at 5:51 PM, Richard W. Solomon w1ksz@earthlink.net
wrote:

That is not true.  If it were DOA and the seller would not take it back
post paid you could file a "not as described" on the seller and eBay would
refund the price.  eBay and Paypal offer pretty good buyer protection.

Someone here said the seller uses multiple IDs.  It is more likely that one
person is making these and offering to multiple people who  then sell them
on eBay.  This is the way it works in China, a popular design gets made
and then is sold by many people.  It is all a cottage industry over there.
Pick any kind of electronic PCB level part, say a stepper motor driver
and you see the same exact part from 20 different sellers not one seller
with 20 IDs.    (Well that is the general case, this specific one might be
different, who knows.)

But so what even if the GPSDO is good only to 1xE10 that is still a very
useful device to own.  Yes some are literally 1,000 times better

You could always build your own.  It is not hard nor is it expensive if you
have a reasonable goal and don't go for state of the art.

Chris Albertson
Redondo Beach, California

No,  my experience with Chinese sellers,  even when you file a "not as
described"  case,  is that eBay will require you to return the item at your
own expense if the seller has stated they will not pay return shipping.

Ebay's attitude was that the seller could just state in their item
description that buyer is to cover return costs and that's it.  Game over.

Which is why you occasionally still see items for peanuts and extortionate
shipping costs, the seller then only has to refund you a couple of dollars
on an item that may have cost you a hundred including shipping.

I ended up getting a total refund of £3 on a £28 item once I'd returned
it and taken shipping into account. Also,  that was a PayPal refund, not a
seller refund because they just refused shipment so eBay refused to refund
as they had no proof of return.

All the above are the reasons why I now rarely if ever buy anything costing
more than a couple of pounds from China unless I know other people have had
good experience with the item and seller.
On 10 Jul 2016 05:46, "Chris Albertson" albertson.chris@gmail.com wrote: