Listen To 64 MHz At Once

November 16, 2022 by Al Williams 27 Comments

We imagine that if [Tech Minds] told us he was listening to the HF bands, we might ask him which one? His reply might just be “All of them.” That’s thanks to the RX-888 MKII SDR he reviewed which delivers a 64 MHz window on the radio spectrum. You can catch the video review, below.

These are not especially inexpensive, but with that bandwidth and 16-bit resolution, it is worth it if you need that kind of horsepower. There is a separate input for VHF signals 64-1700 MHz where the bandwidth is only 10 MHz, but still.

Of course, making a very wideband front end for something like this is non-trivial, so we wonder how the performance is compared to similar-priced units with less bandwidth. On the other hand, it does seem to work well enough in the video. The software used limited the test to a 32 MHz bandwidth, which is still plenty.

Speaking of software, we noticed that the developers of SatDump and SDR++ are not happy with the state of the software for the RX-888. We aren’t sure if this remains a problem, but the device seemed to work well on the video, at least.

There are many options now when it comes to higher-end SDRs. We like the Pluto for both transmitting and receiving. Of course, the RTL-SDR kind of started everything with hobby SDR, but you can’t expect that much bandwidth with one of those.

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Direction-Finding With Help From The Steam Deck

October 21, 2022 by Bryan Cockfield 6 Comments

Direction-finding, or fox hunting, is a popular activity in ham radio circles where a group of people armed with radios attempt to locate a broadcasting source. Besides being a hobby for amateurs, it’s also a necessary tool in the belt of regulators who are attempting to track down violators of the air space. There are a lot of ways to figure out the precise location of a radio transmission, but this one manages to pull it off using both a boat and a Steam Deck, each armed with a software-defined radio.

This project comes to us from [Aaron] who is well known in the amateur radio circles for his SDR-focused Linux distribution called DragonOS; which has all the tools needed for a quality SDR experience, in this case KrakenSDR and DF Aggregator. He’s loaded everything up on a Steam Deck and left that in a secure location on the shore of a lake, while he carries second device with the same software with him on a boat. With the two devices listening for a specific signal, he’s able to quickly zero in on his friend on the shore who is broadcasting on the 70 cm band thanks to the help of all of these software packages.

While ham radio isn’t always known for being a youthful and exciting activity, the advent of software-defined radio and other digital modes seem to be shaking things up in that world. Certainly speeding around a lake on a boat is fun on its own as well, and a fox hunt like this can be done with something as small and simple as a Raspberry Pi too.

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TRX-Duo Is A Red Pitaya Clone For Software Defined Radio

October 9, 2022 by Al Williams 33 Comments

If you’ve noticed the TRX-DUO software-defined radio transceiver, you might have wondered how it stacks up to other choices like Red Pitaya or HackRF. [Tech Minds] obliges with a review of the Red device in the video below.

While this unit isn’t inexpensive, it also isn’t as expensive as some of its competitors. Sure, you can pick up an RTL-SDR dongle for a fraction of the price, but then you miss out on transmitting. The device is pretty powerful compared to a cheap software defined radio:

Frequency: 10 kHz to 60 MHz
CPU: Zynq SoC with a dual-core ARM Cortex A9
RAM: 512 MB
OS: Linux
Connectivity: Ethernet and USB connectivity (WiFi with a dongle)
ADC: 16-bit at 125 MS/s (2 channels)
DAC: 14-bit at 125 MS/s (2 channels)

The board boots off an SD card and there are several to choose from. The video shows two different images. One has a number of applications that run on the device and will also run on a Red Pitaya. The device shows a browser menu with various options and the result is quite impressive. Using the box as a WSPR beacon, it was heard fairly well given the low output power. It was, however, able to hear the world easily.

You can get a less capable Red Pitaya model for about $100 less than the going price. However, for something comparable, you will pay more for the Red Pitaya and — depending on capabilities — perhaps a lot more, although you do get more capability for the increased price.

You can do a lot more with a transmitting SDR — having both transmit and receive opens up many new projects. Of course, canned applications are great, but if you get one of these, you are going to want to try GNU Radio.

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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.