Five-Watt SDR Transceiver for Hams

The availability of cheap SDR hardware created a flourishing ecosystem for SDR software, but a lot of the hardware driving the revolution was still “cheap”. In the last few years, we’ve seen quality gear replacing the TV dongles in many setups, and down-converters designed for them to allow them to work on the ham bands.

But something that’s purpose-built might be a better option if ham radio, particularly the shortwave portion thereof, is your goal. First off, you might want to transmit, which none of the TV dongles allow. Then, you might want a bit of power. Finally, if you’re serious about short-wave, you care more about the audio quality than you do immense bandwidth, so you’re going to want some good filters on the receiving end to help you pull the signal out of all the noise.

rs-hfiq_block_diagram_featuredThe RS-HFIQ 5 W SDR transceiver might be for you. It’s up on Kickstarter right now, and it’s worth looking at if you want a fully open source (schematics, firmware, and software) shortwave SDR rig. It’s also compatible with various open frontends.

The single-board radio isn’t really a full SDR in our mind — it demodulates the radio signal and sends a 96 kHz IQ signal across to your computer’s soundcard where it gets sampled and fully decoded. The advantage of this is that purpose-built audio rate DACs have comparatively high resolution for the money, but the disadvantage is that you’re limited to 96 kHz of spectrum into the computer. That’s great for voice and code transmissions, but won’t cut it for high-bandwidth data or frequency hopping applications. But that’s a reasonable design tradeoff for a shortwave.

Still, an SDR like this is a far cry from how simple a shortwave radio can be. But if you’re looking to build up your own SDR-based shortwave setup, and you’d like to hack on the controls more than on the radio itself, this looks like a good start.

Cache Shortwave Signals for Later with this SDR Spectrum Grabber

Shortwave listening has always been a mainly nocturnal hobby. To get the real DX, one had to wait for favorable ionospheric conditions after sunset and spend hours twisting knobs while straining to pick voices from half a planet away out of the noise. But who has time for that in today’s world? And what of the poor city-dwelling SWL, with antenna limitations and often elevated noise floor in the urban jungle?
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BST-1 Car Shortwave Receiver

Commuting is a pain. Luckily, nearly every car has some sort of radio or other audio player to while away the hours stuck in traffic. However, most of those radios sport AM and FM bands, along with a weather band and–maybe–a long wave band. What if you prefer shortwave?

[Thomas] posted a review of the BST-1, a car-friendly shortwave receiver. The device is made to mount out of sight–presumably near an external antenna. It beams the shortwave signal to the car’s FM radio. The control is a small key fob and even if you aren’t interested in the radio itself, the user interface design is somewhat interesting.

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Seeing the Truly Invisible with DIY Shortwave UV Imaging

We’ve all seen how to peel IR filters off digital cameras so they can see a little better in the dark, but there’s so much more to this next project than that. How about being able to see things normally completely outside the visual spectrum, like hydrogen combustion or electrical discharges?

UV Electrical Discharge

[David Prutchi] has just shared his incredible work on making his own shortwave ultraviolet viewers for imaging entirely outside of the normal visible spectrum – in other words, seeing the truly invisible. The project has not only fascinating application examples, but provides detailed information about how to build two different imagers – complete with exact part numbers and sources.

UV-Viewer-SmallIf you’re thinking UV is a broad brush, you’re right. [David Prutchi] says he is most interested in Solar Blind UV (SBUV):

Solar radiation in the 240 nm to 280 nm range is completely absorbed by the ozone in the atmosphere and cannot reach Earth’s surface…

Without interference from background light, even very weak levels of UV are detectable. This allows ultraviolet-emitting phenomena (e.g. electrical discharges, hydrogen combustion, etc.) to be detectable in full daylight.

There is more to the process than simply slapping a UV filter onto a camera, but happily he addresses all the details and the information is also available as a PDF whitepaper. [David Prutchi] has been working with imaging for a long time, and with his sharing of detailed build plans and exact part numbers maybe others will get in on the fun. He’s also previously shared full build plans for a Raspberry Pi based multispectral imager, [David’s] DOLPHi Polarization Camera was a finalist in the 2015 Hackaday Prize, and he spoke at the Hackaday SuperConference about the usefulness of advanced imaging techniques for things like tissue analysis in medical procedures, and landmine detection for the purposes of cleaning up hazardous areas.

SDR Cape for BeagleBone

In the old days if you wanted to listen to shortwave you had to turn a dial. Later, you might have been able to tap in a frequency with a keypad. With modern software-defined radio (and the right hardware) you can just listen to the entire high-frequency spectrum at one time. That’s the idea behind KiwiSDR, an open source daughterboard (ok, cape) for the BeagleBone.

The front end covers 10 kHz to 30 MHz and has a 14-bit converter operating at 65 MHz. There is a Xilinx Artix-7 A35 FPGA onboard and a GPS, too. The design is open source and on GitHub.

The interface uses the OpenWebRX project for a powerful HTML 5 interface. You can see a video of its operation below or, if you can get one of the four available slots, you can listen online. From a network point of view, the demo station in Canada worked best for us. However, there are also stations in New Zealand and Sweden.

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Secret Radio Stations by the Numbers

One thing has stayed with the James Bond movie franchise through the decades: Mr. Bond always has the most wonderful of gadgets. Be it handheld, car-based, or otherwise, there’s always something to thrill that is mostly believable.

The biggest problem with all of those gadgets is that they mark Commander Bond as an obvious spy. “So Mr. Bond, I see you have a book with many random five character groups. Nothing suspicious about that at all!” And we all know that import/export specialists often carry exploding cufflinks or briefcases full of unknown electronics in hidden compartments.

Just as steganography hides data in plain sight, the best spy gadgets are the ones that don’t seem to be a spy gadget. It is no wonder some old weapons are little more than sticks or farm implements. You can tell a peasant he can’t have a sword, but it is hard to ban sticks.

Imagine you were a cold war era spy living in a hostile country with a cover job with Universal Exports. Would you rather get caught with a sophisticated encryption machine or an ordinary consumer radio? I’m guessing you went with the radio. You aren’t the only one. That was one of the presumed purposes to the mysterious shortwave broadcasts known as number stations. These were very common during the cold war, but there are still a few of them operating.
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Minimal Mighty Mite

If you’re getting started building your own ham radio gear, it’s hard to imagine a more low-tech transmitter than the Mighty Mite, but [Paul Hodges, KA5WPL] took it one step further and rolled his own variable capacitor. (That’s the beer can with tape and alligator clips that you see on the left.)

A Mighty Mite is barely a radio at all. One transistor, capacitor, crystal and inductor in the form of a bunch of wire wrapped around a pill bottle form a minimalist oscillator, and then by keying this on and off with a switch, you’re sending Morse code. [Bill Meara], of the Soldersmoke Podcast, has been a passionate advocate of the Mighty Mite, suggesting that it can be made by scrounging the 3.57954 MHz colorburst crystal from an old analog TV set, which tunes the radio to a legal frequency for ham radio operators. (It will also probably work with other low-MHz crystals from your junkbox, but it won’t necessarily be legal.)

michigan_mighty_mite_schematicIf the crystal is “easily” scavengeable, and the rest of the radio is easily home-made, the tuning capacitor (obtainable from old AM/FM radios) can become the sticking point. So [Paul] cut up two aluminum “beverage” cans, wrapped the inner one in electrical tape, hooked up wires and made his own variable capacitor. By sliding the cans in or out so that more or less of them overlap, he can tune the radio to exactly the crystal’s natural frequency.

If you’re interested in building a Mighty Mite, you should definitely look at the topic on Soldersmoke. There are more build instructions online as well as plans for an optional filter to take off the harmonics if you’re feeling ambitious.

If you’re not a Morse code wiz, we can’t help but note that you could replace the key with a simple FET (we’d use a 2N7000, but whatever) and then you’ve got the radio under microcontroller control. Scavenge through Hackaday’s recent Morse code projects for ideas, and we’re sure you’ll come up with something good.

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