Re: [time-nuts] eBay GPS antenna test.

[Bob kb8tq]

Hi

I think you probably will have to move up to around $500 or so (and 
still shop pretty hard) to find a Zephyr Geodetic 2 in excellent condition. 
A Novatel 703 Pinwheel would also be on the list of things to watch for. 

If you find a proper (L1 / L2 / L5 ) GNSS receiver with a pps out in working 
shape for $500, go for it. They tend to be quite a bit above that price. Most
of what is in the $400 to $1000 range are L1 / L2 GPS only devices. Even
with them, finding one that will do timing is a bit tough. 

Bob

> On Feb 17, 2018, at 3:07 PM, Trevor N.  wrote:
> 
> It's still extremely rare to see a low-priced used triple-frequency
> antenna on ebay. For less than US$300 I've only spotted extremely
> beat-up Zephyr Geodetic Model 2s and a few Leica AX1203+ GNSS (only
> the "+GNSS" model is triple-frequency) (there is one up right now).
> 
>  I've seen at least one Zephyr 2 listing that had a picture of a
> Zephyr 1 attached (look for the bigger bump in the top center on the
> model 2).
> 
> I have yet to see a triple-frequency receiver for under $500
> 
> 
> John Green wpxs472 at gmail.com wrote:
>> Just so people don’t get to down on eBay antennas:
>> 
>> I have gotten some deals on eBay I just couldn't have gotten elsewhere.
>> That is a nice looking antenna. A bit pricey for my budget. I thought just
>> north of $100 for a used Leica choke ring job was about it. The Trimble
>> antenna I got recently had issues, so I got it cheap and fixed the
>> mechanical problems. I think I have one of those HP timing antennas I have
>> heard mentioned here. I need to dig it up. I think I also have a PC Tel
>> model around somewhere. I still haven't gotten the top off that Chinese
>> made one that bit the dust at 12 volts. I need to get it apart somehow. I
>> think it can probably be repaired. I can at least let the seller know what
>> went bad.
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[time-nuts] eBay GPS antenna test.

[Trevor N .]

It's still extremely rare to see a low-priced used triple-frequency
antenna on ebay. For less than US$300 I've only spotted extremely
beat-up Zephyr Geodetic Model 2s and a few Leica AX1203+ GNSS (only
the "+GNSS" model is triple-frequency) (there is one up right now).

  I've seen at least one Zephyr 2 listing that had a picture of a
Zephyr 1 attached (look for the bigger bump in the top center on the
model 2).

I have yet to see a triple-frequency receiver for under $500


John Green wpxs472 at gmail.com wrote:
>Just so people don’t get to down on eBay antennas:
>
>I have gotten some deals on eBay I just couldn't have gotten elsewhere.
>That is a nice looking antenna. A bit pricey for my budget. I thought just
>north of $100 for a used Leica choke ring job was about it. The Trimble
>antenna I got recently had issues, so I got it cheap and fixed the
>mechanical problems. I think I have one of those HP timing antennas I have
>heard mentioned here. I need to dig it up. I think I also have a PC Tel
>model around somewhere. I still haven't gotten the top off that Chinese
>made one that bit the dust at 12 volts. I need to get it apart somehow. I
>think it can probably be repaired. I can at least let the seller know what
>went bad.
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Re: [time-nuts] eBay GPS antenna test.

[John Green]

Bob wrote:  Hi

Just so people don’t get to down on eBay antennas:

I have gotten some deals on eBay I just couldn't have gotten elsewhere.
That is a nice looking antenna. A bit pricey for my budget. I thought just
north of $100 for a used Leica choke ring job was about it. The Trimble
antenna I got recently had issues, so I got it cheap and fixed the
mechanical problems. I think I have one of those HP timing antennas I have
heard mentioned here. I need to dig it up. I think I also have a PC Tel
model around somewhere. I still haven't gotten the top off that Chinese
made one that bit the dust at 12 volts. I need to get it apart somehow. I
think it can probably be repaired. I can at least let the seller know what
went bad.


Virus-free.
www.avast.com

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Re: [time-nuts] eBay GPS antenna test.

[Bob kb8tq]

Hi

Just so people don’t get to down on eBay antennas: 

https://www.ebay.com/itm/Antcom-Active-L1-L2-Choke-Ring-Antenna-Item-123GM1215A-XT-1-AUTOFARM-AGLEADER/302630180910?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649
 
<https://www.ebay.com/itm/Antcom-Active-L1-L2-Choke-Ring-Antenna-Item-123GM1215A-XT-1-AUTOFARM-AGLEADER/302630180910?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649>

Was indeed brand new in box. The pictures don’t quite give credit to the 
branding
on the antenna. It was shipped directly from the outfit that put the great big
letters on it. Price was a bit less than eBay would have you think, but still a 
bit
more than the ones from China. No idea if they will be selling any more. 

An L1 / L2 choke ring is a much better bet pattern wise than the patch 
antennas. It also is a
great big heavy monster of a thing to mount somewhere ….

On the down side, like a lot of what you see, it’s GPS only. At least by spec, 
it will 
not pass the full Glonass L1 or L2  bands. That may be why it turned up as 
“brand new but 
we’re unloading it”.  What the passband *really* looks like ….. we’ll see ….

Bob

> On Feb 14, 2018, at 12:23 AM, Bill Hawkins  wrote:
> 
> Learned tonight that J. P. Morgan got his start by buying 25 K defective
> rifles for %3.50 each and selling them to the Army for $25 each. You
> have no reason to trust a listing.
> 
> Bill Hawkins
> 
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob
> kb8tq
> Sent: Tuesday, February 13, 2018 12:04 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] eBay GPS antenna test.
> 
> Hi
> 
> 
>> On Feb 13, 2018, at 12:06 PM, Clint Jay  wrote:
>> 
>> Agreed but stock numbers on boxes and packets  are usually Arabic 
>> numerals or a barcode. It's also possible the seller used a stock 
>> image which can be copied and pasted into Google web search to track 
>> down the maker or at least a distributor who has data.
> 
> The seller did post a number of images for the part that was listed. The
> gotcha is that the part that arrived is not labeled the same way as the
> part that was listed.
> Since the device also has issues, the big question is if it has any
> connection to the part in the listing at all. 
> 
> The seller seems to have been doing GPS stuff for a while. He also has a
> very good approval rating. My guess is: this isn't the first time he's
> seen a bump in the road. I'd bet he's got the ability to check this and
> that out to see what is what. 
> The seller *does* matter when you buy this stuff. That's true no matter
> what you are getting. No matter how good they are, problems do come up.
> The question is always how well they address them. We tend to dump
> pretty hard on these guys. I'm not sure that's always warrantied. 
> 
> Bob
> 
> 
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Re: [time-nuts] eBay GPS antenna test results.

[Bob kb8tq]

Hi

As with any antenna mods, the issue isn’t so much doing them as proving that
what you did had this or that effect. A lot of what you are paying for on the 
fancy
antennas is the fact that indeed they went through some sort of validation 
process
on top of the design process. 

An equally valid point is that the standard “telecom” antennas likely are no 
great
thing for low angle multi path either. That is one of several reasons we tend 
to 
like cranking up the elevation mask on our TBolts. 

If you are going for the “I want something that does it all” approach. You 
would want
an antenna that does at least L1 / L2 / L5 and covers the GPS and Glonas parts 
of 
the bands. So far, those have not shown up as $100 new in box items ….. Given
that the price of gear covering all of that is still “a bit high” (even as a 
home brew 
SDR), I’m not sure it matters a whole lot at this point. 

Bob

> On Feb 15, 2018, at 9:13 AM, jimlux  wrote:
> 
> On 2/15/18 6:04 AM, Bob kb8tq wrote:
>> Hi
>> There are a number of reasons to believe that these antennas are worse
>> than the typical “telecom GPS” antenna for L1 only duty driving a TBolt.
>> If you are going to do L1 / L2 work with something like a NetRS, then indeed
>> you will need a dual band antenna. These (the $99 ones)  are the lowest cost
>> “new in box” L1 / L2 antennas that I have seen. One would *guess* that their
>> close to horizon multi path rejection is not quite as good as a Trimble 
>> Zephyr,
>> a Novatel Pinwheel, or a choke ring. The ones from China
>>  also don’t cost $1800 to $6000 when new either …
> 
> 
> one could probably improvise something that serves as a choke ring, or 
> elevation fence.  The infamous JPL Helibowl is pretty simple, and has pretty 
> good rejection of signals near the horizon.
> 
> See, e.g. Page 143 in GPS/GNSS Antennas, by Rao.  (I found it on google
> 
> https://books.google.com/books?id=nL-YFWLQrPIC&pg=PA143&lpg=PA143&dq=helibowl+antenna&source=bl&ots=U-7Y3TMIQw&sig=D4xZVMmv73XkCAH_8KkMegMnxX4&hl=en&sa=X&ved=0ahUKEwjbjLGTjKjZAhVM7WMKHdYPC5sQ6AEIMTAB#v=onepage&q=helibowl%20antenna&f=false
> 
> Oddly, it cites to C.Y Cheng, Numerical Electromagnetic Modeling of a Small 
> Aperture Helical-Fed Reflector Antenna, Masters thesis, Ohio University, Aug 
> 1998.
> 
> Good luck finding that one on-line
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Re: [time-nuts] eBay GPS antenna test results.

[jimlux]

On 2/15/18 6:04 AM, Bob kb8tq wrote:

Hi

There are a number of reasons to believe that these antennas are worse
than the typical “telecom GPS” antenna for L1 only duty driving a TBolt.
If you are going to do L1 / L2 work with something like a NetRS, then indeed
you will need a dual band antenna. These (the $99 ones)  are the lowest cost
“new in box” L1 / L2 antennas that I have seen. One would *guess* that their
close to horizon multi path rejection is not quite as good as a Trimble Zephyr,
a Novatel Pinwheel, or a choke ring. The ones from China
  also don’t cost $1800 to $6000 when new either …




one could probably improvise something that serves as a choke ring, or 
elevation fence.  The infamous JPL Helibowl is pretty simple, and has 
pretty good rejection of signals near the horizon.


See, e.g. Page 143 in GPS/GNSS Antennas, by Rao.  (I found it on google

https://books.google.com/books?id=nL-YFWLQrPIC&pg=PA143&lpg=PA143&dq=helibowl+antenna&source=bl&ots=U-7Y3TMIQw&sig=D4xZVMmv73XkCAH_8KkMegMnxX4&hl=en&sa=X&ved=0ahUKEwjbjLGTjKjZAhVM7WMKHdYPC5sQ6AEIMTAB#v=onepage&q=helibowl%20antenna&f=false

Oddly, it cites to C.Y Cheng, Numerical Electromagnetic Modeling of a 
Small Aperture Helical-Fed Reflector Antenna, Masters thesis, Ohio 
University, Aug 1998.


Good luck finding that one on-line
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Re: [time-nuts] eBay GPS antenna test results.

[Bob kb8tq]

Hi

There are a number of reasons to believe that these antennas are worse
than the typical “telecom GPS” antenna for L1 only duty driving a TBolt. 
If you are going to do L1 / L2 work with something like a NetRS, then indeed
you will need a dual band antenna. These (the $99 ones)  are the lowest cost 
“new in box” L1 / L2 antennas that I have seen. One would *guess* that their
close to horizon multi path rejection is not quite as good as a Trimble Zephyr,
a Novatel Pinwheel, or a choke ring. The ones from China
 also don’t cost $1800 to $6000 when new either …

Bob

> On Feb 15, 2018, at 4:31 AM, Christoph Kopetzky  wrote:
> 
> Moin,
> are in the meantime any experiences with these gps antennas from the china 
> seller (ms_geo)?
> I found two type of them from the same seller:
> 
> 1) 
> https://www.ebay.com/itm/High-Precision-L1-L2-GNSS-GPS-GLONASS-BeiDou-RTK-CORS-survey-antenna/162718512935?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649
>  
> 
> this one is the 3.3 - 18 V version with 5 dB antenna gain and 42 dB LNA gain 
> for  appr. 100 US$
> 
> and 
> 
> 2) 
> https://www.ebay.com/itm/High-Precision-GNSS-GPS-GLONASS-BeiDou-RTK-CORS-survey-machine-control-antenna/162710405447
>  
> 
> this one has 3.3 - 10 V  voltage requirement and nearly the same gain values 
> but 85 US$ 
> 
> Does anyone have one oth them up and running?
> 
> Are they much more better as a Symmetricom 58532A antenna ore the puck head 
> variant?
> 
> If yes I would give it also a try but the shipment time from goods from china 
> are very high. Here to Germany there are timeframes from four to eight weeks 
> normal. :(
> 
> But the price 
>  -
> Chris
> Am 13.02.2018 um 03:05 schrieb Bob kb8tq:
>> Hi
>> 
>> Sitting here casually reading the data sheets for some of the modern Trimble
>> survey receivers - they have gone to 7.2V (just below your 7.5V trigger 
>> point) 
>> as an antenna supply voltage. 
>> 
>> Who knows what that might imply relative to this antenna. 
>> 
>> Bob
>> 
>>> On Feb 11, 2018, at 12:44 PM, John Green  
>>>  wrote:
>>> 
>>> They have issued a refund. The seller said that my antenna was defective.
>>> This is kind of a strange outfit. They are in Russia selling Chinese goods,
>>> shipped from China.  Since I don't have to return it, I will disassemble it
>>> to see what went bad. I replied that if he could assure me that it would
>>> work on 12 volts, I might order another.
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Re: [time-nuts] eBay GPS antenna test.

[Bill Hawkins]

Learned tonight that J. P. Morgan got his start by buying 25 K defective
rifles for %3.50 each and selling them to the Army for $25 each. You
have no reason to trust a listing.

Bill Hawkins

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob
kb8tq
Sent: Tuesday, February 13, 2018 12:04 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] eBay GPS antenna test.

Hi


> On Feb 13, 2018, at 12:06 PM, Clint Jay  wrote:
> 
> Agreed but stock numbers on boxes and packets  are usually Arabic 
> numerals or a barcode. It's also possible the seller used a stock 
> image which can be copied and pasted into Google web search to track 
> down the maker or at least a distributor who has data.

The seller did post a number of images for the part that was listed. The
gotcha is that the part that arrived is not labeled the same way as the
part that was listed.
Since the device also has issues, the big question is if it has any
connection to the part in the listing at all. 

The seller seems to have been doing GPS stuff for a while. He also has a
very good approval rating. My guess is: this isn't the first time he's
seen a bump in the road. I'd bet he's got the ability to check this and
that out to see what is what. 
The seller *does* matter when you buy this stuff. That's true no matter
what you are getting. No matter how good they are, problems do come up.
The question is always how well they address them. We tend to dump
pretty hard on these guys. I'm not sure that's always warrantied. 

Bob


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Re: [time-nuts] eBay GPS antenna test.

[Bob kb8tq]

Hi


> On Feb 13, 2018, at 12:06 PM, Clint Jay  wrote:
> 
> Agreed but stock numbers on boxes and packets  are usually Arabic numerals
> or a barcode. It's also possible the seller used a stock image which can be
> copied and pasted into Google web search to track down the maker or at
> least a distributor who has data.

The seller did post a number of images for the part that was listed. The gotcha 
is
that the part that arrived is not labeled the same way as the part that was 
listed.
Since the device also has issues, the big question is if it has any connection 
to
the part in the listing at all. 

The seller seems to have been doing GPS stuff for a while. He also has a very
good approval rating. My guess is: this isn’t the first time he’s seen a bump 
in 
the road. I’d bet he’s got the ability to check this and that out to see what 
is what. 
The seller *does* matter when you buy this stuff. That’s true no matter what you
are getting. No matter how good they are, problems do come up. The question
is always how well they address them. We tend to dump pretty hard on these 
guys. I’m not sure that’s always warrantied. 

Bob

> 
> On 13 Feb 2018 16:18, "Bob kb8tq"  wrote:
> 
>> Hi
>> 
>> That can be a bit harder if the labels are all in Chinese. Maybe posting
>> pictures of the label? That way those (not I) who can read Chinese might
>> spot something that allows a search to proceed.
>> 
>> Bob
>> 
>>> On Feb 13, 2018, at 11:06 AM, Clint Jay  wrote:
>>> 
>>> Sounds like a drop shipping operation, they've found a supplier in China
>>> who is willing to send goods either in plain wrapping without any
>> supplier
>>> name or the name of the agent who's selling it. It can be useful to
>> Google
>>> anything that looks like a part number on the packaging, you'll often
>> find
>>> the main wholesaler or even the manufacturer.
>>> 
>>> On 13 Feb 2018 15:48, "John Green"  wrote:
>>> 
 Bob wrote:  Sitting here casually reading the data sheets for some of
>> the
 modern Trimble
 survey receivers - they have gone to 7.2V (just below your 7.5V trigger
 point)
 as an antenna supply voltage.
 
 Who knows what that might imply relative to this antenna.
 
 After getting my refund, I sent the seller a message saying that I would
 buy another if he could assure me it would work at 12 volts. He replied
 that he needed to get his hands on a couple and do some testing first.
>> The
 antenna that I received seems to be different to the one pictured in the
 eBay listing. At least the labels are different. I get the feeling he is
 kind of a third party dealing with someone in China who is wholesaling
 antennas made by someone else. Who really knows what spec. these are
>> made
 to, or by who. In my former place of employment, we made an SMB
>> terminator.
 Basically, a 75 ohm resistor soldered across the pins of an SMB
>> connector,
 then molded in black plastic. We bought the connectors from a Chinese
 supplier who supplied them in individual plastic bags. We had to cut the
 parts out of the bags before processing, which added a labor step. We
>> tried
 to get the supplier to sell them to us packaged in bulk, but they
>> refused.
 We decided that they were actually buying them from someone else and
>> just
 doing a passthru. The connectors themselves would change from time to
>> time,
 which caused problems in molding, and sometimes caused the electrical
 performance to degrade. Getting parts to reliably meet a specification
>> from
 China can be a problem. I can't even imagine the issues that could arise
 when you try to source an assembly, or completed product.
 
 
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Re: [time-nuts] eBay GPS antenna test.

[Clint Jay]

Oh, and Google has a handy translation tool which does a reasonable job of
translating Chinese text from a jpg image so that's also worth a try.

On 13 Feb 2018 16:18, "Bob kb8tq"  wrote:

> Hi
>
> That can be a bit harder if the labels are all in Chinese. Maybe posting
> pictures of the label? That way those (not I) who can read Chinese might
> spot something that allows a search to proceed.
>
> Bob
>
> > On Feb 13, 2018, at 11:06 AM, Clint Jay  wrote:
> >
> > Sounds like a drop shipping operation, they've found a supplier in China
> > who is willing to send goods either in plain wrapping without any
> supplier
> > name or the name of the agent who's selling it. It can be useful to
> Google
> > anything that looks like a part number on the packaging, you'll often
> find
> > the main wholesaler or even the manufacturer.
> >
> > On 13 Feb 2018 15:48, "John Green"  wrote:
> >
> >> Bob wrote:  Sitting here casually reading the data sheets for some of
> the
> >> modern Trimble
> >> survey receivers - they have gone to 7.2V (just below your 7.5V trigger
> >> point)
> >> as an antenna supply voltage.
> >>
> >> Who knows what that might imply relative to this antenna.
> >>
> >> After getting my refund, I sent the seller a message saying that I would
> >> buy another if he could assure me it would work at 12 volts. He replied
> >> that he needed to get his hands on a couple and do some testing first.
> The
> >> antenna that I received seems to be different to the one pictured in the
> >> eBay listing. At least the labels are different. I get the feeling he is
> >> kind of a third party dealing with someone in China who is wholesaling
> >> antennas made by someone else. Who really knows what spec. these are
> made
> >> to, or by who. In my former place of employment, we made an SMB
> terminator.
> >> Basically, a 75 ohm resistor soldered across the pins of an SMB
> connector,
> >> then molded in black plastic. We bought the connectors from a Chinese
> >> supplier who supplied them in individual plastic bags. We had to cut the
> >> parts out of the bags before processing, which added a labor step. We
> tried
> >> to get the supplier to sell them to us packaged in bulk, but they
> refused.
> >> We decided that they were actually buying them from someone else and
> just
> >> doing a passthru. The connectors themselves would change from time to
> time,
> >> which caused problems in molding, and sometimes caused the electrical
> >> performance to degrade. Getting parts to reliably meet a specification
> from
> >> China can be a problem. I can't even imagine the issues that could arise
> >> when you try to source an assembly, or completed product.
> >>
> >>  >> source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=icon>
> >> Virus-free.
> >> www.avast.com
> >>  >> source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=link>
> >> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
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> >>
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Re: [time-nuts] eBay GPS antenna test.

[Clint Jay]

Agreed but stock numbers on boxes and packets  are usually Arabic numerals
or a barcode. It's also possible the seller used a stock image which can be
copied and pasted into Google web search to track down the maker or at
least a distributor who has data.

On 13 Feb 2018 16:18, "Bob kb8tq"  wrote:

> Hi
>
> That can be a bit harder if the labels are all in Chinese. Maybe posting
> pictures of the label? That way those (not I) who can read Chinese might
> spot something that allows a search to proceed.
>
> Bob
>
> > On Feb 13, 2018, at 11:06 AM, Clint Jay  wrote:
> >
> > Sounds like a drop shipping operation, they've found a supplier in China
> > who is willing to send goods either in plain wrapping without any
> supplier
> > name or the name of the agent who's selling it. It can be useful to
> Google
> > anything that looks like a part number on the packaging, you'll often
> find
> > the main wholesaler or even the manufacturer.
> >
> > On 13 Feb 2018 15:48, "John Green"  wrote:
> >
> >> Bob wrote:  Sitting here casually reading the data sheets for some of
> the
> >> modern Trimble
> >> survey receivers - they have gone to 7.2V (just below your 7.5V trigger
> >> point)
> >> as an antenna supply voltage.
> >>
> >> Who knows what that might imply relative to this antenna.
> >>
> >> After getting my refund, I sent the seller a message saying that I would
> >> buy another if he could assure me it would work at 12 volts. He replied
> >> that he needed to get his hands on a couple and do some testing first.
> The
> >> antenna that I received seems to be different to the one pictured in the
> >> eBay listing. At least the labels are different. I get the feeling he is
> >> kind of a third party dealing with someone in China who is wholesaling
> >> antennas made by someone else. Who really knows what spec. these are
> made
> >> to, or by who. In my former place of employment, we made an SMB
> terminator.
> >> Basically, a 75 ohm resistor soldered across the pins of an SMB
> connector,
> >> then molded in black plastic. We bought the connectors from a Chinese
> >> supplier who supplied them in individual plastic bags. We had to cut the
> >> parts out of the bags before processing, which added a labor step. We
> tried
> >> to get the supplier to sell them to us packaged in bulk, but they
> refused.
> >> We decided that they were actually buying them from someone else and
> just
> >> doing a passthru. The connectors themselves would change from time to
> time,
> >> which caused problems in molding, and sometimes caused the electrical
> >> performance to degrade. Getting parts to reliably meet a specification
> from
> >> China can be a problem. I can't even imagine the issues that could arise
> >> when you try to source an assembly, or completed product.
> >>
> >>  >> source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=icon>
> >> Virus-free.
> >> www.avast.com
> >>  >> source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=link>
> >> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
> >> ___
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> >>
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Re: [time-nuts] eBay GPS antenna test.

[Bob kb8tq]

Hi

That can be a bit harder if the labels are all in Chinese. Maybe posting
pictures of the label? That way those (not I) who can read Chinese might
spot something that allows a search to proceed. 

Bob

> On Feb 13, 2018, at 11:06 AM, Clint Jay  wrote:
> 
> Sounds like a drop shipping operation, they've found a supplier in China
> who is willing to send goods either in plain wrapping without any supplier
> name or the name of the agent who's selling it. It can be useful to Google
> anything that looks like a part number on the packaging, you'll often find
> the main wholesaler or even the manufacturer.
> 
> On 13 Feb 2018 15:48, "John Green"  wrote:
> 
>> Bob wrote:  Sitting here casually reading the data sheets for some of the
>> modern Trimble
>> survey receivers - they have gone to 7.2V (just below your 7.5V trigger
>> point)
>> as an antenna supply voltage.
>> 
>> Who knows what that might imply relative to this antenna.
>> 
>> After getting my refund, I sent the seller a message saying that I would
>> buy another if he could assure me it would work at 12 volts. He replied
>> that he needed to get his hands on a couple and do some testing first. The
>> antenna that I received seems to be different to the one pictured in the
>> eBay listing. At least the labels are different. I get the feeling he is
>> kind of a third party dealing with someone in China who is wholesaling
>> antennas made by someone else. Who really knows what spec. these are made
>> to, or by who. In my former place of employment, we made an SMB terminator.
>> Basically, a 75 ohm resistor soldered across the pins of an SMB connector,
>> then molded in black plastic. We bought the connectors from a Chinese
>> supplier who supplied them in individual plastic bags. We had to cut the
>> parts out of the bags before processing, which added a labor step. We tried
>> to get the supplier to sell them to us packaged in bulk, but they refused.
>> We decided that they were actually buying them from someone else and just
>> doing a passthru. The connectors themselves would change from time to time,
>> which caused problems in molding, and sometimes caused the electrical
>> performance to degrade. Getting parts to reliably meet a specification from
>> China can be a problem. I can't even imagine the issues that could arise
>> when you try to source an assembly, or completed product.
>> 
>> > source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=icon>
>> Virus-free.
>> www.avast.com
>> > source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=link>
>> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
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Re: [time-nuts] eBay GPS antenna test.

[Clint Jay]

Sounds like a drop shipping operation, they've found a supplier in China
who is willing to send goods either in plain wrapping without any supplier
name or the name of the agent who's selling it. It can be useful to Google
anything that looks like a part number on the packaging, you'll often find
the main wholesaler or even the manufacturer.

On 13 Feb 2018 15:48, "John Green"  wrote:

> Bob wrote:  Sitting here casually reading the data sheets for some of the
> modern Trimble
> survey receivers - they have gone to 7.2V (just below your 7.5V trigger
> point)
> as an antenna supply voltage.
>
> Who knows what that might imply relative to this antenna.
>
> After getting my refund, I sent the seller a message saying that I would
> buy another if he could assure me it would work at 12 volts. He replied
> that he needed to get his hands on a couple and do some testing first. The
> antenna that I received seems to be different to the one pictured in the
> eBay listing. At least the labels are different. I get the feeling he is
> kind of a third party dealing with someone in China who is wholesaling
> antennas made by someone else. Who really knows what spec. these are made
> to, or by who. In my former place of employment, we made an SMB terminator.
> Basically, a 75 ohm resistor soldered across the pins of an SMB connector,
> then molded in black plastic. We bought the connectors from a Chinese
> supplier who supplied them in individual plastic bags. We had to cut the
> parts out of the bags before processing, which added a labor step. We tried
> to get the supplier to sell them to us packaged in bulk, but they refused.
> We decided that they were actually buying them from someone else and just
> doing a passthru. The connectors themselves would change from time to time,
> which caused problems in molding, and sometimes caused the electrical
> performance to degrade. Getting parts to reliably meet a specification from
> China can be a problem. I can't even imagine the issues that could arise
> when you try to source an assembly, or completed product.
>
>  source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=icon>
> Virus-free.
> www.avast.com
>  source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=link>
> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
> ___
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> mailman/listinfo/time-nuts
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>
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Re: [time-nuts] eBay GPS antenna test.

[Bob kb8tq]

Hi

China does a lot of things through a marketplace process. Lots of guys with
piles of this or that. Any sort of product you get in (to them) small volume 
likely goes through this kind of arrangement. Buying OCXO’s and other 
timing gear is every bit as vulnerable to the “this one today, something 
different tomorrow” process that results. 

This sort of process is also vulnerable to the “grabbed the wrong box” problem.
The good ones are in this box and the others are in that box. I’m in a hurry 
and ….

It’s well worth remembering that we *are* (or should be)  paying a very low 
price 
for most of this stuff. It is unfortunate that paying a higher price does not 
seem to guarantee a better outcome. 

Bob

> On Feb 13, 2018, at 8:00 AM, John Green  wrote:
> 
> Bob wrote:  Sitting here casually reading the data sheets for some of the
> modern Trimble
> survey receivers - they have gone to 7.2V (just below your 7.5V trigger
> point)
> as an antenna supply voltage.
> 
> Who knows what that might imply relative to this antenna.
> 
> After getting my refund, I sent the seller a message saying that I would
> buy another if he could assure me it would work at 12 volts. He replied
> that he needed to get his hands on a couple and do some testing first. The
> antenna that I received seems to be different to the one pictured in the
> eBay listing. At least the labels are different. I get the feeling he is
> kind of a third party dealing with someone in China who is wholesaling
> antennas made by someone else. Who really knows what spec. these are made
> to, or by who. In my former place of employment, we made an SMB terminator.
> Basically, a 75 ohm resistor soldered across the pins of an SMB connector,
> then molded in black plastic. We bought the connectors from a Chinese
> supplier who supplied them in individual plastic bags. We had to cut the
> parts out of the bags before processing, which added a labor step. We tried
> to get the supplier to sell them to us packaged in bulk, but they refused.
> We decided that they were actually buying them from someone else and just
> doing a passthru. The connectors themselves would change from time to time,
> which caused problems in molding, and sometimes caused the electrical
> performance to degrade. Getting parts to reliably meet a specification from
> China can be a problem. I can't even imagine the issues that could arise
> when you try to source an assembly, or completed product.
> 
> 
> Virus-free.
> www.avast.com
> 
> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
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[time-nuts] eBay GPS antenna test.

[John Green]

Bob wrote:  Sitting here casually reading the data sheets for some of the
modern Trimble
survey receivers - they have gone to 7.2V (just below your 7.5V trigger
point)
as an antenna supply voltage.

Who knows what that might imply relative to this antenna.

After getting my refund, I sent the seller a message saying that I would
buy another if he could assure me it would work at 12 volts. He replied
that he needed to get his hands on a couple and do some testing first. The
antenna that I received seems to be different to the one pictured in the
eBay listing. At least the labels are different. I get the feeling he is
kind of a third party dealing with someone in China who is wholesaling
antennas made by someone else. Who really knows what spec. these are made
to, or by who. In my former place of employment, we made an SMB terminator.
Basically, a 75 ohm resistor soldered across the pins of an SMB connector,
then molded in black plastic. We bought the connectors from a Chinese
supplier who supplied them in individual plastic bags. We had to cut the
parts out of the bags before processing, which added a labor step. We tried
to get the supplier to sell them to us packaged in bulk, but they refused.
We decided that they were actually buying them from someone else and just
doing a passthru. The connectors themselves would change from time to time,
which caused problems in molding, and sometimes caused the electrical
performance to degrade. Getting parts to reliably meet a specification from
China can be a problem. I can't even imagine the issues that could arise
when you try to source an assembly, or completed product.


Virus-free.
www.avast.com

<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
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Re: [time-nuts] eBay GPS antenna test results.

[Clay Autery]

I would be extremely surprised if ebay does not rule in your favor.
I've only had ONE case EVER opened against me, and it was CLEARLY not a 
valid case, but eBay still made me give the buyer his money back IN FULL 
to include shipping.

eBay almost always picks the buyer over the seller.

73,
Clay, KY5G


On 02/11/18 08:07, John Green wrote:

I opened a "Not as listed" case and heard back from the seller. They said
that the antenna is definitely 3.3 to 18 volts and have sold several that
are in operation. They wanted to know specifically how I tested the
antenna, why I thought it shorted, and if I actually ever hooked it to a
GPS receiver. I answered as best I could but haven't heard anything
further. eBay seems to like pictures or videos. Though problematic, I
suppose I could take some pictures. I offered to do so in my response to
the seller. They do seem a bit more responsive to buyer complaints than in
previous years. I recently ordered a 64 Gb micro SD card from a US based
seller. I got a message from eBay stating that they had removed the listing
but that everything should be OK. I never received the SD card, and after a
month, checked PayPal and saw that I had been charged for it. I contacted
eBay and they refunded my money the next day.
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Re: [time-nuts] eBay GPS antenna test results.

[Bob kb8tq]

Hi

Sitting here casually reading the data sheets for some of the modern Trimble
survey receivers - they have gone to 7.2V (just below your 7.5V trigger point) 
as an antenna supply voltage. 

Who knows what that might imply relative to this antenna. 

Bob

> On Feb 11, 2018, at 12:44 PM, John Green  wrote:
> 
> They have issued a refund. The seller said that my antenna was defective.
> This is kind of a strange outfit. They are in Russia selling Chinese goods,
> shipped from China.  Since I don't have to return it, I will disassemble it
> to see what went bad. I replied that if he could assure me that it would
> work on 12 volts, I might order another.
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[time-nuts] eBay GPS antenna test results.

[John Green]

They have issued a refund. The seller said that my antenna was defective.
This is kind of a strange outfit. They are in Russia selling Chinese goods,
shipped from China.  Since I don't have to return it, I will disassemble it
to see what went bad. I replied that if he could assure me that it would
work on 12 volts, I might order another.
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Re: [time-nuts] eBay GPS antenna test results.

[Bob kb8tq]

Hi

Well, good news / bad news I guess. The seller is at least responding to your
input. They also did not come back with something about “there is no voltage
spec”. It’s quite possible that they are the 5th person in a chain of sellers 
and
a substitution got made (unknown to them) at seller 3. 

I’d hook up a power supply, a current meter and a couple of clip leads. Shoot a
cell phone picture at 5V and one a second one at 10V. That’s all it should 
take. 
If you have more than one DVM, that would make things even more clear. 

Bob

> On Feb 11, 2018, at 9:07 AM, John Green  wrote:
> 
> I opened a "Not as listed" case and heard back from the seller. They said
> that the antenna is definitely 3.3 to 18 volts and have sold several that
> are in operation. They wanted to know specifically how I tested the
> antenna, why I thought it shorted, and if I actually ever hooked it to a
> GPS receiver. I answered as best I could but haven't heard anything
> further. eBay seems to like pictures or videos. Though problematic, I
> suppose I could take some pictures. I offered to do so in my response to
> the seller. They do seem a bit more responsive to buyer complaints than in
> previous years. I recently ordered a 64 Gb micro SD card from a US based
> seller. I got a message from eBay stating that they had removed the listing
> but that everything should be OK. I never received the SD card, and after a
> month, checked PayPal and saw that I had been charged for it. I contacted
> eBay and they refunded my money the next day.
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[time-nuts] eBay GPS antenna test results.

[John Green]

I opened a "Not as listed" case and heard back from the seller. They said
that the antenna is definitely 3.3 to 18 volts and have sold several that
are in operation. They wanted to know specifically how I tested the
antenna, why I thought it shorted, and if I actually ever hooked it to a
GPS receiver. I answered as best I could but haven't heard anything
further. eBay seems to like pictures or videos. Though problematic, I
suppose I could take some pictures. I offered to do so in my response to
the seller. They do seem a bit more responsive to buyer complaints than in
previous years. I recently ordered a 64 Gb micro SD card from a US based
seller. I got a message from eBay stating that they had removed the listing
but that everything should be OK. I never received the SD card, and after a
month, checked PayPal and saw that I had been charged for it. I contacted
eBay and they refunded my money the next day.
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Re: [time-nuts] eBay GPS antenna test results.

[Bob kb8tq]

Hi

Ok, the antenna in the pictures on the listing *does* have labeling in English 
and it sure looks like it says 3.3 to 18V on the antenna. Certainly you have 
(and the rest of us may soon have) a case for “not as shown” in terms of 
what you got (and we get).

Bob

> On Feb 9, 2018, at 9:31 PM, John Green  wrote:
> 
> Bob wrote:
> Is it labeled 3.3 to 18V on the antenna?
> 
> No, the writing on the antenna is all Chinese. The specs published on eBay
> state that it is.
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[time-nuts] eBay GPS antenna test results.

[John Green]

Bob wrote:
Is it labeled 3.3 to 18V on the antenna?

No, the writing on the antenna is all Chinese. The specs published on eBay
state that it is.
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Re: [time-nuts] eBay GPS antenna test results.

[Dana Whitlow]

I would surmise that the antenna has (or rather had) a protection network
to protect against voltage spikes or surges.  Your description of events
seems consistent with an triggered SCR crowbar circuit, and the 2nd
attempt at the higher current limit shorted the SCR.  Note that this may
not have been a regular SCR, but perhaps a NPN/PNP pair hooked up
to emulate an SCR.   If you can find evidence of such a circuit, it may
be replaceable or simply removable, leaving the antenna fully functional.

Assuming this works, do keep the supply voltage down to something
reasonable like 5 or 6 volts.   Excess voltage will result in unneeded
heat generation in whatever regulator the antenna uses, shortening
its life.

Dana



On Fri, Feb 9, 2018 at 5:00 PM, Dr. David Kirkby <
drkir...@kirkbymicrowave.co.uk> wrote:

> On 9 February 2018 at 21:43, John Green  wrote:
>
> > To those who doubted that the antenna was actually a 3.3 to 18 volt
> design,
> > it seems you were correct. Today, I hooked it up to a variable power
> supply
> > and slowly raised the DC voltage fed to the antenna. It began to pull
> > current at about 2.9 volts and at 3.3 volts, took about 40 mA. I
> continued
> > to slowly raise the voltage. At about 7.5 volts, the current suddenly
> > dropped to 10 mA. At just below 12 volts, it suddenly increased to 80 mA
> > and the supply went into current limit. I increased the current limit to
> > 130 mA and repeated the exercise. Everything went as above until I
> reached
> > 12 volts and the current went to 130 mA and the supply went into current
> > limit. Lowering the voltage didn't lower the current. I disconnected it,
> > waited a minute, and tried again. Yep, shorted. It would have worked well
> > with the T bolt, but would have blown anyway if I tried to use it with my
> > 12 volt supply and bias T. I guess I will get inside it somehow to see if
> > it can be repaired. My first attempt ended in failure. I guess I need a
> > bigger screwdriver with which to pry the top off. I am going to contact
> the
> > seller and tell them it was not as advertised. I kind of doubt that will
> > get me anything, but it won't hurt to try. There is a saying about
> > experience being a cruel teacher. You get the results first, and the
> lesson
> > after. Oh well.
> >
>
>
> You should not open it up, but open an eBay case for item not as described.
> If it said it would do 3-18 V, but does not, then its not as described, and
> you should get your money back. The chances are the seller will not want to
> arrange collection, so you will probably get to keep it anyway. But you
> should get a refund before opening it up.
>
> Dave
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Re: [time-nuts] eBay GPS antenna test results.

[Dr. David Kirkby]

On 9 February 2018 at 21:43, John Green  wrote:

> To those who doubted that the antenna was actually a 3.3 to 18 volt design,
> it seems you were correct. Today, I hooked it up to a variable power supply
> and slowly raised the DC voltage fed to the antenna. It began to pull
> current at about 2.9 volts and at 3.3 volts, took about 40 mA. I continued
> to slowly raise the voltage. At about 7.5 volts, the current suddenly
> dropped to 10 mA. At just below 12 volts, it suddenly increased to 80 mA
> and the supply went into current limit. I increased the current limit to
> 130 mA and repeated the exercise. Everything went as above until I reached
> 12 volts and the current went to 130 mA and the supply went into current
> limit. Lowering the voltage didn't lower the current. I disconnected it,
> waited a minute, and tried again. Yep, shorted. It would have worked well
> with the T bolt, but would have blown anyway if I tried to use it with my
> 12 volt supply and bias T. I guess I will get inside it somehow to see if
> it can be repaired. My first attempt ended in failure. I guess I need a
> bigger screwdriver with which to pry the top off. I am going to contact the
> seller and tell them it was not as advertised. I kind of doubt that will
> get me anything, but it won't hurt to try. There is a saying about
> experience being a cruel teacher. You get the results first, and the lesson
> after. Oh well.
>


You should not open it up, but open an eBay case for item not as described.
If it said it would do 3-18 V, but does not, then its not as described, and
you should get your money back. The chances are the seller will not want to
arrange collection, so you will probably get to keep it anyway. But you
should get a refund before opening it up.

Dave
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Re: [time-nuts] eBay GPS antenna test results.

[Bob kb8tq]

Hi

Is it labeled 3.3 to 18V on the antenna?

Bob

> On Feb 9, 2018, at 4:43 PM, John Green  wrote:
> 
> To those who doubted that the antenna was actually a 3.3 to 18 volt design,
> it seems you were correct. Today, I hooked it up to a variable power supply
> and slowly raised the DC voltage fed to the antenna. It began to pull
> current at about 2.9 volts and at 3.3 volts, took about 40 mA. I continued
> to slowly raise the voltage. At about 7.5 volts, the current suddenly
> dropped to 10 mA. At just below 12 volts, it suddenly increased to 80 mA
> and the supply went into current limit. I increased the current limit to
> 130 mA and repeated the exercise. Everything went as above until I reached
> 12 volts and the current went to 130 mA and the supply went into current
> limit. Lowering the voltage didn't lower the current. I disconnected it,
> waited a minute, and tried again. Yep, shorted. It would have worked well
> with the T bolt, but would have blown anyway if I tried to use it with my
> 12 volt supply and bias T. I guess I will get inside it somehow to see if
> it can be repaired. My first attempt ended in failure. I guess I need a
> bigger screwdriver with which to pry the top off. I am going to contact the
> seller and tell them it was not as advertised. I kind of doubt that will
> get me anything, but it won't hurt to try. There is a saying about
> experience being a cruel teacher. You get the results first, and the lesson
> after. Oh well.
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Re: [time-nuts] eBay GPS antenna test results.

[John Green]

To those who doubted that the antenna was actually a 3.3 to 18 volt design,
it seems you were correct. Today, I hooked it up to a variable power supply
and slowly raised the DC voltage fed to the antenna. It began to pull
current at about 2.9 volts and at 3.3 volts, took about 40 mA. I continued
to slowly raise the voltage. At about 7.5 volts, the current suddenly
dropped to 10 mA. At just below 12 volts, it suddenly increased to 80 mA
and the supply went into current limit. I increased the current limit to
130 mA and repeated the exercise. Everything went as above until I reached
12 volts and the current went to 130 mA and the supply went into current
limit. Lowering the voltage didn't lower the current. I disconnected it,
waited a minute, and tried again. Yep, shorted. It would have worked well
with the T bolt, but would have blown anyway if I tried to use it with my
12 volt supply and bias T. I guess I will get inside it somehow to see if
it can be repaired. My first attempt ended in failure. I guess I need a
bigger screwdriver with which to pry the top off. I am going to contact the
seller and tell them it was not as advertised. I kind of doubt that will
get me anything, but it won't hurt to try. There is a saying about
experience being a cruel teacher. You get the results first, and the lesson
after. Oh well.
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and follow the instructions there.