mindctrl

Hi guys,

I was just wondering, and I know this is probably a really complicated project that I wouldn't want to get involved with, but I'm going to ask anyway because I am curious. Has anybody ever heard of a project where you build your own GPS receiver?

I looked on Google and I couldn't find anything. I found a whole bunch of information about making custom cables for your GPS, etc. but nothing to deal with the actual fabrication of a GPS receiver.

I ask this question because eventually I want to build a project that needs to have a relatively exact location sensor in it, using the GPS system. I don't want to bother with using a big hunk of equipment that has tons of features I don't need. I just need something that maybe has a 4x20 LCD display readout with a couple of buttons to toggle through menus.

I look forward to your knowledgeable responses. Thanks and have a great night. Happy Martin Luther King Day!

--mindctrl

kinjalgp

Building your own GPS receiver would be quite tough job. It is very complicated and would be rather expensive than what is readily avilable. All you need to do is poll the receiver through its serial port using any microcontroller interface, get the readings, decode it and display it on LCD which is also interfaced with the uC. Don't go for building the receiver yourself.

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mindctrl

What exactly about it is so tough? Are there special "encoder" chips that are only available to certain manufacturers with a government contract, or something? I guess what I'm trying to say, is how exactly is this such a hard project? How would it be any different from building any other kind of receiver? What kind of complications are there?

bmcculla

The High frequency stuff is not easy - lots of math and lots of testing required. I'ts also really hard to buy that sort of IC except in high volumes. These sorts of ICs also tend to be in tiny packages that arn't hand solderable.

If you want GPS you'll probably have to shell out some money for a pre built module. Using a module shouldn't be too hard though. I think Sparkfun.com has some.

checkmate

Well, maybe you are googling with the wrong keywords. I checked "GPS Development Kit" and received lots of related hits.

Nigel Goodwin

If you don't know why it's difficult, you probably don't have a chance of making one from scratch!, assuming you could get the special chips required?. Certainly doing so would cost a great deal more money than buying one.

Would you build your own PC motherboard from scratch?, or your own Pentium 4 processor?.

As already suggested, you can buy GPS modules which you can then build into your own projects, this makes for a relatively simple construction, with all the expensive, complicated, parts ready done.

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TheOne

Like Nigel said a GPS receiver won't be easy. If you never worked around designing circuits at 1600MHz before and the necessary test equipment, you will have very little chance to get it working. Also GPS receivers must have ultra low noise front-ends as you dealing with signal levels -120dBm and lower. Then there is still the decoding etc. etc.

I posted my design of a GPS amplifier before. The combline filter in there needs 1pF variable capacitors to do the tuning on the resonators. So you can get an idea how critical things become at higher frequencies, not to mention pcb layout. Without a network analyzer to align the filter it would be almost impossible to get the alignment correct.

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