Re: [time-nuts] Good GPSDO on eBay?

[Chris Albertson]

My experience is different.  When I received a broken item from China, it
was damaged in shipment because it was poorly packed, the seller told be to
keep the broken part because he did not want to pay to ship something he
would just toss in the trash.

eBay's current policy is given here:
http://pages.ebay.com/help/policies/money-back-guarantee.html
It says that for items not as described the seller pays for return
shipping.   It seems that what you did was go through paypal who might had
a different policy they need to handle transactions outside of eBay

On Sun, Jul 10, 2016 at 2:23 AM, Clint Jay  wrote:

> 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"  wrote:
>
> > On Sat, Jul 9, 2016 at 5:51 PM, Richard W. Solomon 
> > wrote:
> >
> > > What a deal, if it arrives DOA, return shipment is on
> > > your nickel. I would look elsewhere.
> >
> >
> > 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
> > ___
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> > To unsubscribe, go to
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> > and follow the instructions there.
> >
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>



-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] Good GPSDO on eBay?

[Bob Camp]

Hi

The EEVB guys have been going around on these GPSDO’s for about a year
now. Lots of people have tried to get refunds on them. Pretty much every trick 
in the
book (replacement is in the mail …. need one more piece of information from you 
…
shipping clerk in the hospital with bubonic plague …) seems to have been used. 
If the
tricks work, they run you past the refund period stated and … poof … no refund.

We often jump on auction site sellers for some pretty minor things. That tends 
to 
turn this into a “they are all crooks” sort of discussion. A number of these 
guys do
indeed care about selling stuff. The do indeed honor their warranty. They stay 
in 
business under the same name for years and years. Those are the good guys. 
There *is* a difference. 

Bob

> On Jul 10, 2016, at 12:36 AM, Chris Albertson  
> wrote:
> 
> On Sat, Jul 9, 2016 at 5:51 PM, Richard W. Solomon 
> wrote:
> 
>> What a deal, if it arrives DOA, return shipment is on
>> your nickel. I would look elsewhere.
> 
> 
> 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
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Re: [time-nuts] Good GPSDO on eBay?

[Clint Jay]

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"  wrote:

> On Sat, Jul 9, 2016 at 5:51 PM, Richard W. Solomon 
> wrote:
>
> > What a deal, if it arrives DOA, return shipment is on
> > your nickel. I would look elsewhere.
>
>
> 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
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>
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[time-nuts] Good GPSDO on eBay?

[Mark Sims]

I don't think there is a way to control the loop parameters except maybe some 
PFORTH commands.   The Trimble units can be put into holdover via software.  
The Symmetricom units require you to disconnect the antenna (or possibly use a 
SCPI command to manually set the DAC voltage...  Lady Heather does this with 
the Symmetricoms).

Trimble's save the survey in EEPROM,  Symmetricom's do not.  You can manually 
enter a position and stop the survey.

I got bare boards (one for $40!) since I bought them just to get Lady Heather 
working with them.  If you want to pay $30 - $60 extra to get one in a box is 
up to you and the bulgeosity of your wallet multiplied by your coefficient of 
lazy bastardness and divided by the Q factor of your box stash.  


I have not done any ADEV measurements on them,  but here a couple of links to 
EEVBLOG users that have.  It looks like they could use a little tuning.  One 
guy claims the Symmetricom oscillators have around 10 dB better phase noise  
(around 3dB worse than a HP-10811) than the Trimbles  YMMV in the 
oscillator phase noise sweepstakes.
http://www.eevblog.com/forum/projects/a-look-at-my-symmetricom-gpsdo-(ocxo-furuno-receiver)/?action=dlattach;attach=227310;image
http://www.eevblog.com/forum/projects/a-look-at-my-symmetricom-gpsdo-(ocxo-furuno-receiver)/?action=dlattach;attach=206950;image

-

> How good is the OCXO? Can you adjust the loop tuning parameters for best 
stability with the individual OCXO?  If not, does the loop cross over 
from the OCXO to the GPS at an appropriate tau, or does it exhibit the 
notorious "crossed over too early" hump in the xDEV plots?  Does it 
store its surveyed location or does it need to do a new survey every 
time it is powered up

  
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Re: [time-nuts] Good GPSDO on eBay?

[Charles Steinmetz]

Mark wrote:


Charles,

You are confusing these units with those made by that ham in China (can't remember his 
callsign, begins with a "B").   The guts of these boxes is a telco GPDDO board 
made by either Trimble or Symmetricom (you can tell because of the 6.0V power 
requirement).And that reference to a Thunderbolt in his Ebay listing seems to refer 
to him comparing the output of these  to his Thunderbolt,  not that the oscillator in 
them came out of a Thunderbolt.


Thanks, Mark, I stand corrected.  That also means it will have a PLL, 
not an FLL.


How good is the OCXO? Can you adjust the loop tuning parameters for best 
stability with the individual OCXO?  If not, does the loop cross over 
from the OCXO to the GPS at an appropriate tau, or does it exhibit the 
notorious "crossed over too early" hump in the xDEV plots?  Does it 
store its surveyed location or does it need to do a new survey every 
time it is powered up?


Finally, is there a good reason to pay $160 for one the seller has put 
in a box, or can you buy the board for much less and do that yourself?


Best regards,

Charles


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Re: [time-nuts] Good GPSDO on eBay?

[Charles Steinmetz]

Michael wrote:


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


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

Charles


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Re: [time-nuts] Good GPSDO on eBay?

[Chris Albertson]

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

> What a deal, if it arrives DOA, return shipment is on
> your nickel. I would look elsewhere.


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
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[time-nuts] Good GPSDO on eBay?

[Mark Sims]

All the affordable GPSDOs out there are surplus telecom devices...  
Thunderbolts,  Z38xx's,  NTP, etc.   They were built to rigorous telco 
standards and can be excellent performers.  Just because they are surplus, does 
not make them junk.   

The latest round of surplus GPSDOs to hit the market are these "UCCM" units.   
They started out at around $50 and after people figured out what they were and 
how to use them the price jumped to $100+ (Thunderbolts and Z3801A's did the 
same thing,  now a surplus one can set you back  $300-$400.  I suspect that 
these will follow the same path) You can find the UCCM devices as bare boards 
or built up into boxes.   As far as real money,  a surplus $100 unit or new 
$500+ unit?  What's in your wallet?  The UCCM based devices should not be 
confused with or compared to some home-brew GPSDO cobbled together in a similar 
looking box. 

--
> 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. 
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Re: [time-nuts] Good GPSDO on eBay?

[bownes]

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 Jul 9, 2016, at 23:06, Bob Stewart  wrote:
> 
> 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 
> 
> 
> At 04:40 PM 7/9/2016, Richard Mogford wrote:
>> This looks like a good beginner's GPSDO on eBay: 172148560746
>> 
>> "This is GPS Disciplined Clock made with trimble GPSDO Board.Full 
>> tested by Agilent 53132A with US-012 option and Ex-ref from trimble 
>> thunderbolt GPSDO."
>> 
>> 
>>   The seller says it has a sine wave output and is accurate from
>>   10e-11 to 10e-12.
>> 
>> Any thoughts?
>> 
>> Richard
>> 
>> ___
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> 
> 
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Re: [time-nuts] Good GPSDO on eBay?

[Bob Stewart]

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 <dimi...@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:
>This looks like a good beginner's GPSDO on eBay: 172148560746
>
>"This is GPS Disciplined Clock made with trimble GPSDO Board.Full 
>tested by Agilent 53132A with US-012 option and Ex-ref from trimble 
>thunderbolt GPSDO."
>
>
>      The seller says it has a sine wave output and is accurate from
>      10e-11 to 10e-12.
>
>Any thoughts?
>
>Richard
>
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Re: [time-nuts] Good GPSDO on eBay?

[Charles Steinmetz]

Richard wrote:


This looks like a good beginner's GPSDO on eBay: 172148560746

"This is GPS Disciplined Clock made with trimble GPSDO Board.Full tested
by Agilent 53132A with US-012 option and Ex-ref from trimble thunderbolt
GPSDO."

  The seller says it has a sine wave output and is accurate from
  10e-11 to 10e-12.

Any thoughts?


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


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Re: [time-nuts] Good GPSDO on eBay?

[Dimitri.p]

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:

This looks like a good beginner's GPSDO on eBay: 172148560746

"This is GPS Disciplined Clock made with trimble GPSDO Board.Full 
tested by Agilent 53132A with US-012 option and Ex-ref from trimble 
thunderbolt GPSDO."



 The seller says it has a sine wave output and is accurate from
 10e-11 to 10e-12.

Any thoughts?

Richard

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[time-nuts] Good GPSDO on eBay?

[Mark Sims]

Charles,

You are confusing these units with those made by that ham in China (can't 
remember his callsign, begins with a "B").   The guts of these boxes is a telco 
GPDDO board made by either Trimble or Symmetricom (you can tell because of the 
6.0V power requirement).And that reference to a Thunderbolt in his Ebay 
listing seems to refer to him comparing the output of these  to his 
Thunderbolt,  not that the oscillator in them came out of a Thunderbolt.

--
> 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.
  
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Re: [time-nuts] Good GPSDO on eBay?

[Michael Wouters]

"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
 wrote:
> Richard wrote:
>
>> This looks like a good beginner's GPSDO on eBay: 172148560746
>>
>> "This is GPS Disciplined Clock made with trimble GPSDO Board.Full tested
>> by Agilent 53132A with US-012 option and Ex-ref from trimble thunderbolt
>> GPSDO."
>>
>>   The seller says it has a sine wave output and is accurate from
>>   10e-11 to 10e-12.
>>
>> Any thoughts?
>
>
> 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
>
>
>
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Re: [time-nuts] Good GPSDO on eBay?

[Richard W. Solomon]

What a deal, if it arrives DOA, return shipment is on 
your nickel. I would look elsewhere.

73, Dick, W1KSZ

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Richard Mogford
Sent: Saturday, July 09, 2016 4:40 PM
To: time-nuts@febo.com
Subject: [time-nuts] Good GPSDO on eBay?

This looks like a good beginner's GPSDO on eBay: 172148560746

"This is GPS Disciplined Clock made with trimble GPSDO Board.Full tested by 
Agilent 53132A with US-012 option and Ex-ref from trimble thunderbolt GPSDO."


  The seller says it has a sine wave output and is accurate from
  10e-11 to 10e-12.

Any thoughts?

Richard

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[time-nuts] Good GPSDO on eBay?

[Mark Sims]

They are based upon a telco surplus "UCCM" GPSDO board.   Both Symmetricom and 
Trimble made (mostly) compatible units.  I prefer the Trimble units...  they 
store their settings in EEPROM.  The Symmetricom units don't... and have to do 
a long re-survey every time you power them up.   Plus the firmware in the 
Symmetricom units has a couple of minor glitches (occasionally drops a time 
stamp output message and can send the time stamp message in the middle of other 
message outputs).   That said,  the Symmetricom is rumored to have a slightly 
better oscillator)... but it is driven by a 6V to 12V DC-DC converter that is 
known to be somewhat unreliable.  I have not measured the output ADEVs, etc.


A little shopping on Ebay (search Trimble GPSDO) will turn up some units for 
less money.   I bought one of these and it arrived quickly and safely in good 
condition (BTW, you used to be able to get them for $50):
http://www.ebay.com/itm/Trimble-GPS-Receiver-GPSDO-10MHz-1PPS-GPS-Disciplined-Clock-/121966793020?hash=item1c65c9913c:g:TTgAAOSwVllXHYRU
There are unscrupulous sellers shipping damaged units.

This thread on EEVBLOG covers the units pretty well:
http://www.eevblog.com/forum/projects/a-look-at-my-symmetricom-gpsdo-(ocxo-furuno-receiver)/

I now have Lady Heather working with both models.

  
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[time-nuts] Good GPSDO on eBay?

[Richard Mogford]

This looks like a good beginner's GPSDO on eBay: 172148560746

"This is GPS Disciplined Clock made with trimble GPSDO Board.Full tested 
by Agilent 53132A with US-012 option and Ex-ref from trimble thunderbolt 
GPSDO."



 The seller says it has a sine wave output and is accurate from
 10e-11 to 10e-12.

Any thoughts?

Richard

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