Category: Other

Reprogramming a €15 USB Audio Dial to work as an SDR VFO Knob

Thank you to Tysonpower (aka Manuel DO5TY) for submitting information about how he's managed to convert a cheap €14.33 USB audio control dial into a VFO tuning knob for use in SDR programs like SDR-Console V3. He writes:

I sometimes miss a VFO Knob while using my SDRs, especially with SSB Signals or CW where you need to adjust the Frequency very fine.

Because of that I got myself an Audio Dial with USB, reverse engineered it somewhat and wrote a new Firmware for the STM32 used in the USB Dial.

It all worked out and it now simulates a mouse wheel with three different scroll speeds. There is also a Mute Function when you long press the Button.

I had a lot of fun during this project, even when it was a lot of time just for a VFO Knob :)

Manuel's blog post goes into deeper detail on how he reverse engineered the knob and how he re-programmed the STM32 microprocessor. He also includes the HEX file if you want to purchase the same unit and reflash it. His video below shows the modified knob in action.

[EN subs] VFO Knopf für SDRs aus einem Lautstärkeregler

Experimenting with an Ultrasonic Sensor Connected to an Airspy HF+

Software defined radios can have many more applications other than just radio. For example, it's possible to connect an ultrasonic sensor which outputs a waveform at some frequency above DC directly to the input of an SDR. We can then simply treat the sensor output as an RF signal, and view it in any SDR compatible software that shows us a spectrum. Normally you'd use a microcontroller with ADC to process the output of these sensors, but using an SDR makes visualizing and experimenting with these sensors much easier.

Over on YouTube W1VLF has uploaded a video showing his experiments with an ultrasonic sensor connected to his Airspy HF+. In his experiment he places the Airspy HF+ with directly connected ultrasonic sensor in one room, and sets up an ultrasonic emitter in another room. He then uses SDR# to view the 24 kHz ultrasonic sensor signal output on the computer. As he moves the sensor around it's possible to clearly see the doppler shift of the ultrasonic sound waves on the waterfall.

In the past we've also posted about Jan de Jong who experimented with using a piezo speaker connected to an SDRplay RSP1A to detect the ultrasonic navigation sounds from bats.

AirSpy Discovery Its not just for RF anymore

Tech Minds: LoRa Text Chat with Two Othernet Dreamcatcher Boards

Back in the middle of last year we posted about Othernet's Dreamcatcher hardware and the LoRa chat application. The Dreamcatcher is Othernet's receiver and computing platform that is designed for receiving their satellite data broadcast. It is currently available for US$79.

Although the Othernet datacast is one way receive only, the Dreamcatcher board uses a LoRa radio chipset that has TX capabilities that can be leveraged for experimental purposes. One experimental piece of software that they developed is a chat application that works with two Dreamcatcher boards. It allows you to initiate a text based chat between two boards using the on board LoRa radio chips.

The TechMinds YouTube channel has recently released a video demonstrating the chat application in action, and the video shows how to set up, install and use it too. We note that since our post last year, the Dreamcatcher board has gone through a revision and no longer includes an LCD screen. The company name has also changed from "Outernet" to "Othernet".

What can you do with two Othernet Dreamcatcher Boards?

Tysonpower Reviews A Cheap 15€ DAB/DAB+ USB Receiver Dongle that Generates an MP3 Stream

Thank you to Tysonpower who wanted to share his review of a cheap 15€ DAB/DAB+ receiver USB dongle that he found on eBay.de (we also found the same device on eBay.com for US$23.99).  The device is not an SDR, but it receives BAND III DAB/DAB+ at 160-240 MHz and generates an MP3 stream which can be played back on any MP3 capable device such as a PC, single board computer or car head unit.

His review notes that the dongle works well. When you plug it in the device shows up as a storage device. You then simply press a button to automatically search for DAB+ channels, and then choose one of the mp3 stream files that will show up to play live DAB+ audio on your device. In his video he also gives a quick tear down, showing that it uses a FCI FC8080 demodulator and a MVSilicon 32-bit Micro with audio FFT accelerator.

While RTL-SDR dongles can also be used to receive DAB+ cheaply with software like SDR-J and welle.io, this may be a simpler method since it can be used on any device that can play MP3s.

Note that Tysonpowers video is narrated in German, with English subtitles. He also has a short blog post with images from the tear down.

[EN subs] DAB+ für nur 15€ Nachrüsten! - Digitalradio für alle MP3 fähigen Geräte mit USB

Preview: GNU Radio 3.8 Running on an Un-Rooted Android Smartphone

Over on Twitter and YouTube Bastian Bloessl (@bastibl) have been posting teaser shots and videos of GNU Radio 3.8 running on an un-rooted Android device. Unfortunately there doesn't yet seem to be any word yet on how he's been able to do this, but we guess  that the details will all be released in due time, possibly on his blog.

GNU Radio is an open source digital signal processing (DSP) toolkit which is often used in cutting edge radio applications and research, and to implement decoders, demodulators and various other SDR algorithms.

GNU Radio 3.8 on un-rooted Android receiving FM w/ HackRF (take 2)

cuSignal: Easy CUDA GPU Acceleration for SDR DSP and Other Applications

The RAPIDS cuSignal project is billed as an ecosystem that makes enabling CUDA GPU acceleration in Python easy. Scipy is a Python library that is filled with many useful digital signal processing (DSP) algorithms. The cuSignal documentation notes that in some cases you can directly port Scipy signal functions over to cuSignal allowing you to leverage GPU acceleration.

In computing, most operations are performed on the CPU (central processing unit). However, GPU's (graphical processing units) have been gaining popularity for general computing as they can perform many more operations in parallel compared to CPUs. This can be used to significantly accelerate DSP code that is commonly used with SDRs.

In particular the developers have already created a notebook containing some examples of how cuSignal can be used with RTL-SDRs to accelerate an FFT graph. There are various other DSP examples in the list of notebooks too. According to the benchmarks in the notebooks, the GPU computation times are indeed much faster. In the benchmarks they appear to be using a high end NVIDIA P100 GPU, but other NVIDIA graphics cards should also show a good speedup. 

The cuSignal code is based on CUDA, so for any GPU acceleration code to work you'll need to have an NVIDIA based GPU (like a graphics card) with a Maxwell or newer core.

We note that in the future we'll be investigating how this could be used to speed up the passive radar algorithms that are used in the KerberosSDR. It may also be useful for running DSP code quickly on a $99 NVIDIA Jetson Nano single board computer.

NVIDIA Tesla P100. A high end $3000+ GPU.
NVIDIA Tesla P100. A high end $3000+ GPU.

The Malachite-DSP: A $195 Russian Made Portable Wideband SDR Receiver with Touch Screen

Over on the SWLing.com blog we've seen news about the release of a new Russian designed and made portable software defined radio called the "Malachite-DSP". The Malachite-DSP is an "all-in-one" portable SDR that is controlled via a touch screen and two control knobs. It covers 0.1 MHz to 1000 MHz with a bandwidth of up to 160 kHz, and the custom software supports all common modulation types. The whole device consumes 300mA and is powered by a Li-ion cell. It's marketed as a modern DEGEN and TECSUN replacement, so it appears to be targeting the HF short wave listening (SWL) customer.

Production appears to be small, with purchasing currently done by contacting RX9CIM, one of the project creators, directly at his email address (details on this forum post). The cost for a fully assembled unit is 12500 Russian Rubles which is 195 USD (not including international shipping). You can also purchase just the PCB without components for 1100 Rubles (17 USD). Importantly the forum post notes to watch out for scammers, who appear to be trying to take fake preorders for the device.

From the components list we can see that this SDR runs on the MSI001 tuner chip, which is the same tuner chip used in the SDRplay line of units. However, unlike the SDRplay units which use a wideband MSi2500 ADC, the Malachite-DSP uses an audio chip as the RF ADC. This provides a 16-bit ADC, resulting in high dynamic range, but at the expense of the available bandwidth which is only 160 kHz. A STM32H743VIT6 with ARM Cortex A7 processor runs what appears to be custom DSP and GUI software. The software doesn't seem to support DRM, but AM, WFM, NFM, LSB, USB are all supported.

The main place for news and discussion on the Malachite-DSP appears to be on a Russian ham radio forum thread. Judging by the fact that the schematic, software and BOM is all freely released, the project appears to be open source. There is also a group on the Russian Facebook clone vk.com where some discussion is occurring.

The YouTube videos below are by a Russian reviewers. Be sure to turn on the YouTube closed captioning and auto translation feature if you want to follow along in English.

😲ПРИЕМНИК КОТОРЫЙ ЛОВИТ ВСЁ!!!💥🔝 ЭТО ВАМ НЕ Degen и Tecsun ВСТРЕЧАЙТЕ НОВЫЙ МАЛАХИТ DSP V2💯🆕

SDR приемник МАЛАХИТ DSP

The Malachite-DSP reminds us a bit of the unreleased PantronX Titus II SDR, which is supposed to be a low cost (aiming for less than $100 USD) 100 kHz - 2 GHz tablet screen based SDR that was supposed to make DRM reception more popular. However the Titus II hardware has never eventuated since it's initial news in 2016, and at this time appears to be a dead project.

Video About Receiving The Othernet Satellite Data Service: Free APRS, News, Weather

The Othernet project aims to bring live data such as news, weather, video, books, Wikipedia articles and audio broadcasts to the world via cheap receivers and a free satellite service. Although an internet connection provides the same data, Othernet's satellite broadcast is receivable in remote areas, will continue working in disasters, and costs nothing to continually receive roughly 100-200 MB of data a day. The trade off is that the service is downlink only, so the data that you get is only what is curated by the Othernet team. Currently the service is only available in North America and Europe, but service to other areas in the world may eventuate in the future.

We've posted about this project a few times in the past, as previously they used an L-band satellite service that was received by RTL-SDR dongles. However, these days they operate using LoRa hardware chips on the Ku-band.

Over on YouTube the TechMinds YouTube channel has just uploaded a video that demonstrates the Othernet service being received from the UK via their Dreamcatcher hardware. In particular he shows off the APRS feature which sends any APRS message containing the string "OUTNET" to the Othernet satellite stream. Later in the video he also shows the news articles, weather data, Wikipedia and audio data that was received.

OTHERNET - Free Data Anywhere - For everyone!