[time-nuts] anyone tried the cheap Lea-6T modules seen on eBay?
michael.cook at sfr.fr
Sat Nov 29 03:37:31 EST 2014
> Le 25 nov. 2014 à 19:29, Joseph Gray <jgray at zianet.com> a écrit :
> 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.
If you are thinking of replacing the patch antenna with a connector to external antenna as I did, be careful of mechanical bonding. For practical purposes I had place the 5 pin through hole SMA on the top of the module. This meant that I had to run a short connection up through the original patch antenna hole to connect to the board trace. Error. It worked fine, but while boxing for use as an NTP source I inadvertently put pressure on that wire and ripped off the board trace. So my NTP source has been relegated to parts.
Maybe better to have the wire running on the top.
> Joe Gray
> On Nov 25, 2014 9:15 AM, "Mike Cook" <michael.cook at sfr.fr> wrote:
>> You may have seen them as in
>> 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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