[time-nuts] Building a GPSDO & trouble using Jupiter-T

Magnus Danielson magnus at rubidium.dyndns.org
Wed Feb 1 22:50:24 UTC 2012

On 01/02/12 21:32, Chris Albertson wrote:
> On Wed, Feb 1, 2012 at 1:29 AM, Tom Van Baak<tvb at leapsecond.com>  wrote:
>> Most of the high-end GPS receivers offer faster rates than 1 Hz.
>> This is required for RTK work, for example. It is not interpolation.
>> It is hard and accurate and wonderful and expensive.
> My comments were about the GPS receivers being proposed for use here.
> Like the Jupiter and so on.   Yes some can send NMEA at a high rate
> but they don't receive L2 or look at p-code.

If you do not limit yourself to NMEA you can get L1/L2 C/A and P-code 
and both code and carrier phase in rates higher than 1 Hz. I have such 
receivers, and you can get them as modules.

> I was talking about what IS done with the GPSes you'd likey buy on
> ebay or new for under $100.

Got a good deal for three receivers, so it was not far north of 100 
USD... on ebay. One of those receivers got taken care of by a fellow 
time-nut. So, you can do good deals.

> I read the user manual and they say "dead reckoning"    One of the
> GPSes proposed here even has inputs for a car odometer pulse so the
> dead reckoning algorithm can know if you have change speed.

 From one second to the other, you usually do not change speed or 
direction that much. Your typical receiver will produce both position 
and velocity vector, so Kalman filtering on that isn't too hard.


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