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

[Joseph Gray]

I bought one of those recently. I haven't done more than power it on to see
if it works. I will probably look at it more over Thanksgiving.

Joe Gray
W5JG
On Nov 25, 2014 9:15 AM, "Mike Cook" <michael.cook at sfr.fr> wrote:

> 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_JN&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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