[time-nuts] anyone tried the cheap Lea-6T modules seen on eBay?

[Bob Camp]

Hi

I looked at the boards on the eBay listing. Last time I looked at the layout guidelines for the LEA-6T’s they pretty much said “don’t do it that way” ….

Who knows what they did that board for or why they did it that way.

That’s not to say the boards don’t work. They probably do work. Often guidelines are a bit over restrictive…..

Bob

> On Nov 25, 2014, at 2:41 PM, S. Jackson via time-nuts <time-nuts at febo.com> wrote:
> 
> Bert,
> 
> the LEA-6T actually has software bugs that show up in moving  applications 
> and that need to be handled by the users' software, and they are  selling it 
> for drone applications. Without any monitoring for these bugs the  units 
> may really only be useful for stationary applications.
> 
> Why they would choose the 6T unit instead of a non-T unit at half the price 
> would only be because they got those as surplus really cheap I would  
> think.
> 
> bye,
> Said
> 
> 
> In a message dated 11/25/2014 09:50:12 Pacific Standard Time,  
> time-nuts at febo.com writes:
> 
> A Lea-6T  is only worth any extra money if you are using the sawtooth   
> correction data coming out of it. With out correction a $ 14 unit is just  
> as  
> good.
> Bert Kehren
> 
> 
> In a message dated 11/25/2014  11:25:34 A.M. Eastern Standard Time,  
> michael.cook at sfr.fr  writes:
> 
> You may  have seen them as   in
> <http://www.ebay.fr/itm/Ublox-LEA-6T-GPS-Module-w-Compass-for-APM2-5-APM2-6-
> Flight-Controller-Multirotor-/271641375221?pt=UK_ToysGames_RadioControlled_J
> N&hash=item3f3f1671f5>
> There   are other sellers with the same.
> My idea was to see if one was suitable  as  a 1PPS locking source for my 
> PRS10. The interest for me being  that it powers  directly from a USB 
> connection 
> and can be configured  with the Ublox’s u-center  software, so 
> implementation is a no  brainer.
> All I needed to do was to  replace the patch antenna with an  SMA-F 
> connector and add a wire for the 1PPS.  Despite having less  than ideal 
> antenna 
> position, once the survey was complete  I was  getting +/-20ns jitter on 
> the 1PPS 
> which is within spec and stable  over  the day. 
> However I was most disappointed to see that the 1PPS  output  voltage is 
> only 2.16 +/-0.4V. According to spec it should be  Vcc+/-0.4V and I  have 
> Vcc 
> measuring 3.3V.  I can’t see the  board trace but the measured  voltage is 
> the 
> same on the PPS pad next  to the JST-SH connector and on the GPS  modules 
> pin 
> 28 so it is not a  board issue. Unfortunately this is too low to  tickle 
> the 
> PRS10 1PPS  input. I guess I could add a buffer or AND gate to fix  it, but 
> that  sort of defeats the object and introduces extra jitter and  offset.
> It  is however enough for a Raspberry-Pi GPIO input, so I have  relegated 
> it  
> to NTP PPS. 
> 
> Has anyone out there got one of these and  seen  the same symptoms? Or 
> maybe 
> you have one and it is OK? I’d like to   know.
> 
> You will be able to see from the eBay photos that this a  6T-0-000  version 
> which is an early version and it could be that they  are cheap as  some/all 
> have this defect. So   beware.
> 
> 
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