[time-nuts] GPS SDR (was: FE-.5680A trimming resolution)

SAIDJACK at aol.com SAIDJACK at aol.com
Wed Feb 1 20:02:51 UTC 2012

the ublox will just work when you apply power and have a good antenna. The  
Motorola units have all sorts of idiosyncrasies, such as sometimes taking a 
 very long time to achieve a lock, having the Almanac get corrupted and not 
 lock when the battery backup is getting low, having significantly lower 
signal  sensitivity (every dB can make a massive quality difference when 
running in  challenged environments such as indoor receiption), and the uBlox are 
less  expensive and support NMEA without having to send binary commands to 
the  unit, and ordering a non-timing version of the GPS. The M12M timing  
versions do not support NMEA at all. The uBlox also solders down onto a PCB  
(simpler mounting) and is smaller. Lastly uBlox supports WAAS, which  
Motorola does not, and they achieve an initial lock much faster than M12M due to  
their massive parallel correlators.
Shall we not forget that some uBlox units will support Gallileo with a  
firmware upgrade, and will also be able to be ordered with Glonass capability,  
and have a USB port built-in, and achieve pretty good timing performance in 
 mobile applications that the M12M doesn't handle too well.
That said the Motorola M12M or M12+ still have the best timing performance  
by far of the entire lot when operating, and operated correctly and in  
stationary mode.
So in short: if you need the best timing performance and can fiddle with  
the GPS to make it work and do not need any bells and whistles, then get an  
M12M. If you need the easiest to use and fool-proof GPS: get uBlox.
In a message dated 2/1/2012 11:48:00 Pacific Standard Time,  
tvb at LeapSecond.com writes:

Perhaps this doesn't matter for a one-off hobbyist, but if  you're
making kits or products it can become an important factor.

If  you are inclined to experiment, just for the sake of exploring
as many of  us on the list are, then certainly you'd want to get
a u-blox at some  point. It doesn't have to be right away, but it
is a pretty nice, very  modern, ultra compact, timing receiver.

If low cost is the object it's  hard to beat that MG1613S board.


> What is it these  u-blox device can do that a cheaper Motorola Oncore
> can't?    Depending on the version the Oncore has for 50 to 5 nS
> one-sigma error  on the timing pulses and can do either 1PPS or 100PPS.
>  Single  unit prices are from $18 to $60 very good documentation is
>  available.
> If the u-blox was somehow much better than a  Trimble thunderbolt or
> Motorola Oncore MT12T I'd buy one even at the  above price.   But
> really these older GPSs are already at  the single digtit of
> nanoseconds level and I don't see room for  improvement except....
> If the L2 band is also  used.   This is the way to get order of
> magnitude  improments
> Chris Albertson
> Redondo Beach,  California

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