Choosing a GPS Module
I tend to believe that connecting a GPS module to a computer is a rite of passage for techies. While grabbing your exact coordinates and seeing it on a map is big fun it doesn’t compare to learning about GNSS or GPS systems.
Probably the most useful thing you can do with a GPS module in a home lab is to use it as a time server. Pulses Per Second or PPS is ridiculously accurate. You can achieve this in your home lab relatively cheap.
I am an Amateur Radio operator (General Class) and several protocols such as FT8, FT4, and JS8 rely on very precise timing of less than one second. You can see that my time server is WAY MORE ACCURATE than that.
Other Uses
GPS modules can be found in drones, RC cars and aircraft, and model boats. You can also use them for tracking. In my camper I have a GPS with a cellular hat which texts me its coordinates hourly. Hey, people steal campers.
GPS Selection – Buyer Beware
Probably the best GPS chipsets come from a company called U-blox. Consequently, they are also the most heavily counterfeited modules. If someone is advertising a GPS module where the chip itself costs $100 or more for $25 then you can pretty much guarantee it isn’t authentic.
On the flip side of that many companies might harvest actual U-blox chips and add them to a poorly designed module with no ROM which means you cannot upgrade the chipset firmware.
Even inexpensive chipsets like a U-blox 7020 found in many USB GPS sticks are End Of Life (EOL) chips and are no longer supported.
Case in point. I bought this so called NEO-6M board a couple years ago on Amazon for $12. Just the u-blox chip itself to this day goes for $30-$60 if you can find New Old Stock (NOS). No one is going to spend $30 on a chip then add it to a board and then sell it for $12. You should always check the price of just the chip compared to the total cost of the GPS board you are considering.
So I guess what I am saying is to ensure you are buying an authentic module that has ROM and which allows you to update the chips firmware. Additionally, many modern modules can connect via a USB-C interface which means you don’t need to wire them up with DuPont cables. While that works perfectly fine, it is kind of a kluge when it comes to layout and neatness of your installation.
GPS Bands
There are three bands that GPS operates on:
- L1 – 1575.42 MHz
- L2 – 1227.6 MHz
- L5 – 1176.45 MHz
L5 is the most accurate and you probably should get a receiver with L5 capabilities for future-proofing. Having said that, it seems the Legacy L1 system is going to be around for quite some time.
Cost
I’ll leave this to the question, “What do you intend to do”? If you want to run a time server you probably don’t want a $16 module from AliExpress or Amazon. Oddly enough though, many of those modules do work just fine as time servers.
I strongly recommend buying an authentic u-blox chip for your GPS home lab projects. I get most of mine from Sparkfun. For example, the NEO-F10N is an L1/L5 receiver for about $42. Authentic chip, 1 meter accuracy. It can be used as a time server and it can be powered by a USB-C input of 5V. Additionally it has an SMA plug which makes it real easy to attach an antenna to.
Best of all, the NEO-F10N can be used by itself with u-blox U-Center software. (Windows Only). The photo below depicts U-Center software, however the NEO-F10N uses the U-Center 2 software (not depicted).
In my opinion, the NEO-F10N is the best bang for the buck for the beginner GPS user. It is feature rich and relatively low priced.
Some Recommendations
The GPS on the left is the Adafruit Featherwing which uses an MTK3333 chipset. This is a good and inexpensive GPS module for around $25. It also has a built in ceramic antenna. Additionally, you will need to solder some header pins on and use it with a Raspberry Pi or a USB Serial Converter.
The module on the right is a Sparkfun with a u-blox NEO-M9N chip. Cost is just over $70. This module needs an external antenna. The good news is that you can hook this up to a Windows computer via USB-C and control the GPS with the u-blox U-Center software.
What’s Your Vector, Victor
There is no shortage of GPS modules out there to buy. But almost everything out there that is inexpensive is counterfeit. Even if someone harvested an authentic chip the board they put it on may negatively affect the function of the Chipset.
And of course you CAN buy a cheap GPS board from Amazon or eBay or elsewhere and most of them do work fairly well but I have a problem with not getting what I think I am paying for. And to be honest I have purchased a bunch of cheap modules but they are just dust collectors.
Whether you are running a time server or flying a drone make sure to get a decent quality board. Also take a few minutes to learn what the NMEA sentences mean. That is the text you see when hooked to a serial console.