There are two or three different kinds of typical searches conducted for GPS receiver schematics. A Do It Yourself (DIY) enthusiast, for instance, might do a search for GPS receiver schematics as part of a personal project or hobby. The second category of people likely searching for schematics would be researchers trying to find out what kind of developments have been disclosed via patents already. They would be looking to extend the available technology. A third category of users seeking schematics online would be close cousins of the DIY set. These are the savvy folks wanting to modify something in a GPS gadget they already have.
The DIY Enthusiasts
DIY searches turn up very few references that are useful to the DIY enthusiast or hobbyist. The days of do it yourself kits are pretty much a thing of the past. Anything that is remotely close to something that may be useful is usually quite dated. Most often you would turn up a page that may only look promising. Make sure you look for a date of publication or some hint as to when the information was published. You’ll find these to be as old as the early nineties or the beginning of the current millennium. That kind of dated information would not be useful as the parts used in the schematics would not be available on the market now. I am not sure if the kit business existed in GPS receivers at all. Perhaps it did in the very early part of this developing technology but remember that GPS has been around for four decades now, easily. It has gotten to be so sophisticated that there is not much point in trying to develop your own. The kind of development and testing tools you would need is only affordable for the deep-pockets of the development labs at products companies. The circuit board you would need to make would be quite sophisticated and you would need suitable skills to develop mixed signal boards. Once again, these are in the realm of product company development labs, not the hobbyists. Here is one reference which could have been useful but it was published way back in 2004.
You are able to find user manuals of specific products on the net. A good example is here. There are no details on the product’s internals to let you do any fiddling with the product. Information is available on how to use the product, fit external cables etc. But very little help for this kind of work is available. Because of the issues discussed in the earlier section, it would be actually risky to try to do anything with those internals. Another reason no product maker would give out internals would be to prevent details being disclosed to the competition.
Information for Developers and Patent Searches
As it is essential to disclose complete details of whatever technological advancement the patent applicant is claiming, this is the only kind of search that would yield results. But as I already pointed out, it’s not for the resource deprived hobbyists, but the geeks and techies inside those product development labs. An additional twist to the game is complete information is available from agencies that aggregate such information and its usually is priced. The price may be per piece or based on a subscription fee. Here is one such example. This one is a patent issued in 2007. You can easily find more recent ones. An example here has more complete details available. Searches on Google Scholar and Bing turn up similar patterns.