[time-nuts] Cheap LEA-6T [was: Re: Precise Time transfer and relative position over ashort baseline]

Lars Walenius lars.walenius at hotmail.com
Tue Apr 12 13:08:36 EDT 2016


The reason for the 2V out can be found in Gyros schematic in the eevblog thread. The problem is not the LEA module. The problem is that the LEA output is loaded with a diode (transistor BE) + 33ohm. Down in the eevblog thread a solution with a resistor between the LEA and the transistor base solves the problem and you get almost 3.3V out. Also it is  possible to add an external antenna as seen in the thread.
http://www.eevblog.com/forum/projects/ebay-u-blox-lea-6t-gps-module-teardown-and-initial-test/msg887853/#msg887853

See also: http://www.eevblog.com/forum/projects/ocxo-stable-reference-and-control-voltages/msg891318/#msg891318 for some ADEV and MDEV curves for the LEA-6T with postprocessing of the sawtooth error.

Från: Mike Cook<mailto:michael.cook at sfr.fr>
Skickat: den 12 april 2016 13:03
Till: Discussion of precise time and frequency measurement<mailto:time-nuts at febo.com>
Ämne: Re: [time-nuts] Cheap LEA-6T [was: Re: Precise Time transfer and relative position over ashort baseline]

I tried one of these back in 2014 and found it not hitting specs. 2.16V on 1PPS instead of 3.3V. It died after a few months. Your milage may be better, but they are are old versions so there may be a systemic issue.


> Le 11 avr. 2016 à 20:47, Scott Newell <newell+timenuts at n5tnl.com> a écrit :
>
> At 11:46 AM 4/11/2016, Tom Van Baak wrote:
>> Another way might be to use single-channel common view GPS. I've not checked recently to see if 100 ps is possible over a 1 km baseline. If so that would be a less expensive solution. Someone should dig into the RINEX mode of the ublox 6T. It's on my list but the list is long.
>
> BTW, there are some LEA-6T modules (with patch antenna, compass, 1PPS led, and USB connector) intended for drone autopilot use on eBay for around $30 shipped from China. (Search for "LEA-6T".) Mine showed up on the day of my lightning strike, so I've barely played with it. It has the 6.something ROM, connects to u-center, and appears to output the +/-10 ns sawtooth error correction message and the RTKLIB compatible raw data.
>
> "Gyro" on thr eevblog forum reverse engineered part of the schematic:
>
> http://www.eevblog.com/forum/projects/ebay-u-blox-lea-6t-gps-module-teardown-and-initial-test/
>
>
> --
> newell  N5TNL
>
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