gps

325 Articles

A Super-Simple Standalone WSPR Beacon

June 14, 2024 by 26 Comments

We’ve said it before and we’ll say it again: being able to build your own radios is the best thing about being an amateur radio operator. Especially low-power transmitters; there’s just something about having the know-how to put something on the air that’ll reach across the planet on a power budget measured in milliwatts.

This standalone WSPR beacon is a perfect example. If you haven’t been following along, WSPR stands for “weak-signal propagation reporter,” and it’s a digital mode geared for exploring propagation that uses special DSP algorithms to decode signals that are far, far down into the weeds; signal-to-noise ratios of -28 dBm are possible with WSPR.

Because of the digital nature of WSPR encoding and the low-power nature of the mode, [IgrikXD] chose to build a standalone WSPR beacon around an ATMega328. The indispensable Si5351 programmable clock generator forms the RF oscillator, the output of which is amplified by a single JFET transistor. Because timing is everything in the WSPR protocol, the beacon also sports a GPS receiver, ensuring that signals are sent only and exactly on the even-numbered minutes. This is a nice touch and one that our similar but simpler WSPR beacon lacked.

This beacon had us beat on performance, too. [IgrikXD] managed to hit Texas and Colorado from the edge of the North Sea on several bands, which isn’t too shabby at all with a fraction of a watt.

Thanks to [STR-Alorman] for the tip.

[via r/amateurradio]

Console Calculator Moves One Step Closer To Original Design

May 24, 2024 by 13 Comments

With smartphone apps and spreadsheets being the main ways people crunch their numbers nowadays, there’s not much call for a desktop calculator. Or any other physical calculator, for that matter. Which is all the more reason to appreciate this  Wang 300-series calculator console’s revival through a new electronic backend.

If you haven’t made the acquaintance of the Wang calculator series, [Bob Alexander]’s previous Wang project is a perfect introduction. Despite looking very much like an overbuilt early-70s desktop calculator, what you see in the video below is just a terminal, one of four that could connect to a shared “Electronics Package” where most of the actual computational work was done. The package was big and is currently hard to come by, at least at a reasonable price, but the consoles, with their Nixie displays and sturdy keypads, are relatively abundant.

[Bob]’s previous venture into reviving his console involved embedding a PIC32-based controller, turning it into the standalone desktop calculator it never was. To keep more with the original design philosophy, [Bob]’s second stab at the problem moves much of the same circuitry from inside the console into a dedicated outboard package, albeit one much smaller than the original. The replacement package extends and enhances the console functionality a bit, adding a real-time clock and a Nixie exercise routine to ward off the dreaded cathode poisoning. [Bob] also recreates the original Wang logarithmic method of multiplication and division, which is a nice touch with its distinctive flashing display.

Seeing the Wang console hooked up to a package through that thick cable and Centronics connector is oddly satisfying. We’d love to see [Bob] take this to the logical extent and support multiple consoles, but that might be pushing things a bit.

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[Scott Manley] Explains GPS Jamming

May 19, 2024 by 45 Comments

We always think of [Scott Manley] as someone who knows a lot about rockets. So, if you think about it, it isn’t surprising he’s talking about GPS — after all, the system uses satellites. GPS is used in everything these days, and other forms of navigation are starting to fall by the wayside. However, the problem is that the system is vulnerable to jamming and spoofing. This is especially important if you fear GPS allowing missiles or drones to strike precise targets. But there are also plenty of opportunities for malicious acts. For example, drone light shows may be subject to GPS attacks from rival companies, and you can easily imagine worse. [Scott] talks about the issues around GPS spoofing in the video, which you can see below.

Since GPS satellites are distant, blocking the signal is almost too easy, sometimes happening inadvertently. GPS has technology to operate in the face of noise and interference, but there’s no way to prevent it entirely. Spoofing — where you produce false GPS coordinates — is much more difficult.

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GPS At Any Speed

May 13, 2024 by 40 Comments

[Mellow_Labs] was asked to create a GPS speedometer. It seems simple, but of course, the devil is in the details. You can see the process and the result in the video below.

We have to admit that he does things step-by-step. The first step was to test the GPS module’s interface. Then, he tried computing the speed from it and putting the result on a display. However, testing in the field showed that the display was not suitable for outdoor use.

That prompted another version with an OLED screen. Picking the right components is critical. It struck us that you probably need a fast update rate from the GPS, too, but that doesn’t seem to be a problem. Continue reading “GPS At Any Speed” →

WSPR To The Wind With A Pi Pico High Altitiude Balloon

April 11, 2024 by 19 Comments

They say that if you love something, you should set it free. That doesn’t mean that you should spend any more on it than you have to though, which is why [EngineerGuy314] put together this Raspberry Pi Pico high-altitude balloon tracker that should only set you back about $12 to build.

This simplified package turns a Pico into a tracking beacon — connect a cheap GPS module and solar panel, and the system will transmit the GPS location, system temperature, and other telemetry on the 20-meter band using the Weak Signal Propagation Reporter (WSPR) protocol. Do it right, and you can track your balloon as it goes around the world.

The project is based in part on the work of [Roman Piksayin] in his Pico-WSPR-TX package (which we covered before), which uses the Pico’s outputs to create the transmitted signal directly without needing an external radio. [EngineerGuy314] took this a step further by slowing down the Pico and doing some clever stuff to make it run a bit more reliably directly from the solar panel.

The system can be a bit fussy about power when starting up: if the voltage from the solar panel ramps up too slowly, the Pico can crash when it and the GPS chip both start when the sun rises. So, a voltage divider ties into the run pin of the Pico to keep it from booting until the voltage is high enough, and a single transistor stops the GPS from starting up until the Pico signals it to go.

It’s a neat hack that seems to work well: [EngineerGuy314] has launched three prototypes so far, the last of which traveled over 62,000 kilometers/ 38,000 miles.

PCB of the antenna about to be modded, with components desoldered and different parts of the circuit highlighted

Make A GPS Antenna Compatible With Same Manufacturer’s Receiver

April 3, 2024 by 9 Comments

GPS can be a bit complex of a technology – you have to receive a signal below the noise floor, do quite a bit of math that relies on the theory of relativity, and, adding insult to injury, you also have to go outside to test it. Have you ever wondered how GPS antennas work? In particular, how do active GPS antennas get power down the same wire that they use to send signal to the receiver? Wonder not, because [Tom Verbeure] gifts us a post detailing a mod letting a fancy active GPS antenna use a higher-than-expected input voltage.

[Tom]’s post has the perfect amount of detail – enough pictures to illustrate the entire journey, and explanations to go with all of it. The specific task is modifying a Symmetricom antenna to work with a Symmetricom GPS receiver, which has a puzzling attribute of supplying 12V to the antenna instead of more common 3.3V or 5V. There’s a few possible options detailed, and [Tom] goes for the cleanest possible one – replacing the voltage regulator used inside of the antenna.

With a suitable replacement regulator installed and a protection diode replaced, the antenna no longer registers as a short circuit, and gets [Tom] a fix – you, in turn, get a stellar primer on how exactly active GPS antennas work. If your device isn’t ready to use active GPS antennas, [Tom]’s post will help you understand another GPS antenna hack we covered recently – modifying the Starlink dish to use an active antenna to avoid jamming on the frontlines.

Automatic Position Reporting Over HF Radio

March 27, 2024 by 13 Comments

While most of us carry cell phones that have GPS and other location services, they require a significant amount of infrastructure to be useful. Drive from Washington to Alaska like [Lonney] did a while back, where that infrastructure is essentially nonexistent, and you’ll need to come up with some other solutions to let friends and family know where you are.

A tool called the Automatic Packet Reporting System (APRS) is fairly robust in the very high frequency (VHF) part of the amateur radio spectrum, but this solution still relies on a not-insignificant amount of infrastructure for the limited distances involved with VHF. [Lonney] adapted a few other tools to get APRS up and running in the HF range, letting his friends keep tabs on him even from the most remote locations.

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