[time-nuts] GPS SDR (was: FE-.5680A trimming resolution)
albertson.chris at gmail.com
Wed Feb 1 17:27:30 UTC 2012
On Wed, Feb 1, 2012 at 8:19 AM, Attila Kinali <attila at kinali.ch> wrote:
> On Wed, 01 Feb 2012 09:07:23 -0500
> John Ackermann N8UR <jra at febo.com> wrote:
>> There've been numerous threads on the Gnuradio mailing list about code
>> to receive GPS using the Ettus Research USRP hardware. I don't know
>> whether anyone has actually made it work, but it appears that it's been
>> the subject of quite a few academic projects.
That is the problem with an academic projects typically something like
this would be part of a Master's theses or a senior project. and then
the student graduates and was no more interrest in supporting it.
I thought it might be interresting but then found out you need to buy
$2,000+ worth of hardware for even start experimenting. Open Source
SDR needs to run on a common affordable platform or it will never gain
the critical mass of users that it take to make the project live
longer then a few months.
I think the way to go is to find a commercial GPS chip that has a low
level interface and then build the uP controller using a common
development system. Both the chip and the uP board need to be,
common, well documented and cheap. Then with this you build an open
source thunderbolt type device. An SDR that samples the microwave
RF is going to be un-affordable, even mixing and down converting
microwaves is not so simple as doing the same on HF ham bands. But
there might be low level GPS chip available for cheap.
>From my experience the only way projects like this get started is one
guy works until he has a demo of a proof of concept and can say "Hey
look this sort of works and can do simple things" and then others join
> Yes, i know. That's one of the reasons i said it was not too difficult.
> But i have yet to see a project that builds a GPS receiver based on
> the USRP with complete source. There was the gps-sdr project a few
> years back that was quite advanced, but somewhen in time it just disapeared
> from the net and was never seen again. All others i've seen sofar
> are either functionally incomplete or do not provide the complete source.
> Piecing all the code snipets together that are floating around is
> probably more work then writing something from scratch. At least
> there is enough documentation around. There are nomerous books on
> how GPS works and also quite a few specificaly on how to build
> GPS receivers. If you have access to IEEE papers, then you have
> a huge pool on problems building GPS receivers and how to solve them.
> Attila Kinali
> Why does it take years to find the answers to
> the questions one should have asked long ago?
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