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

[EWKehren at aol.com]

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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