[time-nuts] RasberryPi, timing and GPS receivers

Tom Van Baak tvb at LeapSecond.com
Wed Oct 17 18:42:06 UTC 2012


> Question: What GPS timing module should I go with? No more Motorola  
> Oncore so what's best right now? Who sell modules? What are the price  
> ranges?
> 
> Your comments are most welcome.
> 
> -George, N2FGX

Hi George,

Welcome back to the list; you've been quiet for a long time. This sounds like a great project. I hope you keep us informed with progress and also make the results available.

You should be able to find GPS modules with sub-microsecond 1PPS for $25. Check sparkfun.com or the "Skylab" chip used on the www.leapsecond.com/pages/MG1613S board. This and other chip solutions require SMT/PCB mounting, connectors, external antenna and cabling which can add to the net cost of complexity.

A number of people I know who want an inexpensive, turn-key, sub-microsecond, embedded GPS timing solution continue to chose the Garmin 18x/LVC. These are nice because of the high-gain integrated antenna (they work indoors), compact encapsulated design, and extreme ease of use (5V, ground, 1PPS).

/tvb


> A new LEA6-T single piece cost IIRC 190EUR from the webshop.
> A LEA5-T was IIRC half price.
> 
> And a little caution: the LEA5 modules use considerably more power during
> aquisition than the LEA4 did and the LEA6. IIRC we measured up to 150mA
> (compared to <100mA with LEA4). I don't know the Rasberry, but i guess
> that should be not a proble, but you should check for it nevertheless.
> 
> Attila Kinali

Attila,

I'd say the u-blox 5T or 6T is rather over-kill for George's application, both in price and performance (and learning curve and integration). Remember that the world of NTP is milli- and microseconds. State-of-the-art GPS timing receivers and GPSDO are in the nano- and picosecond accuracy/jitter range.

/tvb





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