[time-nuts] anyone tried the cheap Lea-6T modules seen on eBay?
EWKehren at aol.com
EWKehren at aol.com
Tue Nov 25 12:49:49 EST 2014
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
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
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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