
Homemade GPS Receiver - samlittlewood
http://www.holmea.demon.co.uk/GPS/Main.htm
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samlittlewood
Also, this article references an older project that has (for me) the clearest
description of the theory of GPS:

<http://lea.hamradio.si/~s53mv/navsats/theory.html>

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spitfire
I wish I could upvote this several times over. This is hacker news a thousand
times over, and makes up for all the dotcom, and ruby rubbish you have to wade
through on this site.

Well done sir.

~~~
Create
What I cannot create, I do not understand \-- as quoted in The Universe in a
Nutshell, Richard Feynman

The scientist describes what is; the engineer creates what never was. --
Kármán Tódor

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jgrahamc
I guess this is what it takes to get round the CoCom limit:
<http://blog.jgc.org/2010/11/gaga-1-cocom-limit-for-gps.html>

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calloc
Having done two balloon launches, it is not that hard to find resources that
specify what GPS modules will work and what ones won't work.

We used a

Garmin GPS 18

and it worked flawlessly (other than our night launch, where we recorded
really low freezing temperatures and we think that our GPS froze because it
stopped giving us data).

Our first launch got to 92k+ ft and the GPS kept reporting without issues.

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zb
_The L1 carrier is spread over a 2 MHz bandwidth and its strength at the
Earth's surface is -130 dBm. Thermal noise power in the same bandwidth is -111
dBm, so a GPS signal at the receiving antenna is ~ 20 dB below the noise
floor._

This is slightly misleading; the bandwidth of the _entire signal_ is 2MHz
(it's a 1MHz chip). The bandwidth of the _carrier_ is much narrower - it is
above the noise floor typically by somewhere between about 15 and 50dBHz (you
can see this quite easily on a spectrum analyser). The spread-spectrum part of
the signal is indeed well below the noise floor.

That minor quibble aside, this is a pretty awesome effort for one guy to do
end-to-end.

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caf
Cold start to lock in 2.5 seconds is pretty damn good.

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moe
It's an order of magnitude better than my Samsung Galaxy S can do (when it
gets a lock at all...).

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caf
Yes - it's because of the clever design that means that it doesn't use the
Almanac data, so it doesn't need to wait for it to download.

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Duckpaddle2
Really cool project, seeing hackers who really understand the technology makes
for great reading! Thanks for sharing this!

~~~
VladRussian
great combination of electrical engineering, core physics (classical and if
you want it - GPS does touch SR and GR), programming (at app and VSDL levels).
Such projects should be a regular part of lab curriculum for any engineering
student (including programmers).

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jeremyarussell
Thought this was great, will be trying to make one myself I think. Keep up the
awesome work, I'm keeping your site bookmarked now. (I saw a whole bunch of
other cool stuff.)

