Ham Radio SSB Transceiver Fits In Pocket

December 9, 2021 by Al Williams 32 Comments

Talking about this Chinese ham radio transceiver requires a veritable flurry of acronyms: HF, SSB, QRP, and SDR to start with. [Paul] does a nice job of unboxing the rig and checking it out. The radio is a clone of a German project and provides a low-power radio with a rechargeable battery. You can see his video about the gear below.

SSB is an odd choice for low power operation, although we wonder if you couldn’t feed digital data in using a mode like PSK31 that has good performance at low power. There are several variations of the radio available and they cost generally less than $200 — sometimes quite a bit less.

There isn’t much on the front of the radio. There are a few buttons, a rotary encoder, and an LCD along with a speaker and microphone built-in. There are ports for power to run the radio if you want to not use the battery and a separate port for battery charging. There are also ports for a key, external microphone and speakers, and audio connections that look like they’d work for digital modes. According to commenters, the radio doesn’t have an internal charging circuit, so you have to be careful what you plug into the charging port.

Looking inside, the radio looks surprisingly well made. Towards the end of the video, you can see the radio make some contacts, too. Looks like fun. This is a bit pricey for [Dan Maloney’s] $50 Ham series, but not by much. You might borrow an antenna idea from him, at least. If you prefer something more analog, grab seven transistors and build this SSB transceiver.

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More Software-Defined Radio Projects Using DragonOS

November 3, 2021 by Bryan Cockfield 14 Comments

DragonOS, a Debian-based Linux distribution specifically packaged for software-defined radio functionality, roared onto the wavelengths during the beginnings of the various pandemic lockdowns last year. Since then [Aaron], the creator of the OS, has been busy adding features to the distribution as well as creating plenty of videos which show off its capabilities and also function as how-tos for people who might want to learn about software-defined radio. The latest is a video about using this software to detect radio signals in certain specified spectrums.

This build uses two RTL-SDR devices paired with the DragonOS software suite to automatically detect active frequencies within a specified frequency range and that aslo exceed a threshold measured above the average noise floor. The video includes the setup of the software and its use in detecting these signals, but also includes setup of influxdb and Grafana which provide logging capabilities as well. Using this setup, multiple receivers either local or over the internet can then be configured to dump all the identified frequencies, powers, and time stamps into DragonOS.

[Aaron] has also been helping developers to build the SDR4space.lite application which includes GPS support, so he hopes that in a future video a user will be able to easily associate location to identified frequencies. Projects like these also serve as a reminder that getting into software-defined radio is as easy as buying a $10 USB radio receiver and configuring some free software to do anything that you can imagine like tracking ships and airplanes in real time.

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Phase Coherent Beamforming SDR

August 4, 2021 by Al Williams 16 Comments

The days when software defined radio techniques were exotic are long gone, and we don’t miss them one bit. A case in point: [Laakso Mikko’s] research group has built a multichannel receiver using 21 cheap RTL-SDR dongles to create a phase coherent array. This is useful for everything from direction finding and passive radar or beam forming. The code is also available on GitHub.

The phase coherence does require the dongle’s tuner can turn off dithering. That means the code only works with dongles that use the R820T/2. The project modifies the dongles to use a common clock and a switchable reference noise generator.

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Tuning Into Medical Implants With The RTL-SDR

July 11, 2021 by Tom Nardi 12 Comments

With a bit of luck, you’ll live your whole life without needing an implanted medical device. But if you do end up getting the news that your doctor will be installing an active transmitter inside your body, you might as well crack out the software defined radio (SDR) and see if you can’t decode its transmission like [James Wu] recently did.

Before the Medtronic Bravo Reflux Capsule was attached to his lower esophagus, [James] got a good look at a demo unit of the pencil-width gadget. Despite the medical technician telling him the device used a “Bluetooth-like” communications protocol to transmit his esophageal pH to a wearable receiver, the big 433 emblazoned on the hardware made him think it was worth taking a closer look at the documentation. Sure enough, its entry in the FCC database not only confirmed the radio transmitted a 433.92 MHz OOK-PWM encoded signal, but it even broke down the contents of each packet. If only it was always that easy, right?

The 433 ended up being a coincidence, but it got him on the right track.

Of course he still had to put this information into practice, so the next step was to craft a configuration file for the popular rtl_433 program which split each packet into its principle parts. This part of the write-up is particularly interesting for those who might be looking to pull data in from their own 433 MHz sensors, medical or otherwise

Unfortunately, there was still one piece of the puzzle missing. [James] knew which field was the pH value from the FCC database, but the 16-bit integer he was receiving didn’t make any sense. After some more research into the hardware, which uncovered another attempt at decoding the transmissions from the early days of the RTL-SDR project, he realized what he was actually seeing was the combination of two 8-bit pH measurements that are sent out simultaneously.

We were pleasantly surprised to see how much public information [James] was able to find about the Medtronic Bravo Reflux Capsule, but in a perfect world, this would be the norm. You deserve to know everything there is to know about a piece of electronics that’s going to be placed inside your body, but so far, the movement towards open hardware medical devices has struggled to gain much traction.

Raspberry Pi Hat Adds SDR With High Speed Memory Access

June 20, 2021 by Al Williams 57 Comments

An SDR add-on for the Raspberry Pi isn’t a new idea, but the open source cariboulite project looks like a great entry into the field. Even if you aren’t interested in radio, you might find the project’s use of a special high-bandwidth memory interface to the Pi interesting.

The interface in question is the poorly-documented SMI or Secondary Memory Interface. [Caribou Labs] helpfully provides links to others that did the work to figure out the interface along with code and a white paper. The result? Depending on the Pi, the SDR can exchange data at up to 500 Mbps with the processor. The SDR actually uses less than that, at about 128 Mbps. Still, it would be hard to ship that much data across using conventional means.

On the radio side, the SDR covers 389.5 to 510 MHz and 779 to 1,020 MHz. There’s also a wide tuning channel from 30 MHz to 6 GHz, with some exclusions. The board can transmit at about 14 dBm, depending on frequency and the receive noise figure is under 4.5 dB for the lower bands and less than 8 dB above 3,500 MHz. Of course, some Pis already have a radio, but not with this kind of capability. We’ve also seen SMI used to drive many LEDs.

Remoticon Video: Learning The Basics Of Software-Defined Radio (SDR)

January 19, 2021 by Mike Szczys 8 Comments

Have you dipped your toe into the SDR ocean? While hacker software-defined radio has been a hot topic for years now, it can be a little daunting to try it out for the first time. Here’s your change to get your legs under you with the SDR overview workshop presented by Josh Conway during the 2020 Hackaday Remoticon.

Josh’s presentation starts with a straightforward definition of SDR before moving to an overview of the hardware and software that’s out there. Hardware designs for radios can be quite simple to build, but they’ll be limited to a single protocol — for instance, an FM radio can’t listen in on 433 Mhz wireless doorbell. SDR breaks out of that by moving to a piece of radio hardware that can be reconfigured to work with protocols merely by making changes to the software that controls it. This makes the radio hardware more expensive, but also means you can listen (and sometimes transmit) to a wide range of devices like that wireless doorbell or automotive tire pressure sensors, but also radio-based infrastructure like airplane transponders and weather satellites.

This is the quickstart you want since it explains a lot of topis at just the right depth. The hardware overview covers RTL-SDR, ADALM-PLUTO, HackRF, KerberosSDR, and BladeRF (which we just featured over the weekend used on the WiFi procotol). For software, Josh recaps GQRX, SDR#, SDRAngel, ShinySDR, Universal Radio Hacker, Inspectrum, SigDigger, RPITX, GnuRadio Companion, and REDHAWK. He also takes us through a wide swath of the antenna types that are out there before turning to questions from the workshop attendees.

If SDR is still absent in your toolbox, now’s a great time to give it another look. Once you’ve made it through the ‘hello world’ stage, there’s plenty to explore like those awesome RF Emissions testing tricks we as in another Remoticon talk.

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Doing WiFi With Software Defined Radio

January 16, 2021 by Lewin Day 12 Comments

Software defined radio lets RF hardware take on a broad spectrum of tasks, all based on how that hardware is utilized in code. The bladeRF 2.0 micro xA9 is one such device, packing a fat FPGA with plenty of room for signal processing chains on board. As a demonstration of its abilities, [Robert Ghilduta] set about writing a software-defined WiFi implementation for the platform.

The work is known as bladeRF-wiphy, as it implements the PHY, or physical layer of the WiFi connection, in the 7-layer OSI networking model. Modulation and demodulation of the WiFi signal is all handled onboard the Cyclone V FPGA, with the decoded 802.11 WiFI packets handed over to the Linux mac80211 module which handles the MAC level, or medium access control. Thanks to the capability baked into mac80211, the system can act as either an access point or an individual station depending on the task at hand.

[Robert] does a great job of explaining the why and the how of implementing WiFi modulation on an FPGA, as well as some basics of modem development in both software and hardware. It’s dense stuff, so for those new to the field of software defined radio, consider taking some classes to get yourself up to speed!