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]

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.

[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.

The other issue is, of course, that you have to have a GPS lock for this to work. Inside the urban canyon, you might be better served with a different method. You might think about an accelerometer, but while that’s easy in theory (velocity is the integration of acceleration), in practice, errors and other issues make that a tough way to do it.

The project wraps up with a nice case and some special display modes. We were sorry that the code and STLs were available “on request,” but you’d probably do it differently anyway. This isn’t the first GPS speedometer we’ve seen. Ever wonder how fast your dog is going?