The latest August edition of the RadioWorld Magazine has included an article by James Careless about the use of software defined radios for shortwave radio listening. RadioWorld is a magazine targeted towards radio broadcast owners, managers and engineers all over the world. The article explores SDRplay and RTL-SDR Blog V4 units from the perspective of a shortwave listener new to software defined radios, comparing them to his high-end Sangean ATS-909X2 shortwave digital receiver.
Thank you to Ihar Yatsevich for writing in and sharing with us his open-source WSPR beacon project. The WSPR beacon consists of a custom PCB with ATMega328 microcontroller, GPS module, single transistor amplifier, and Si5351 with TCXO.
The result is a very simple, portable WSPR beacon that can be heard all over the world. However, it appears that no band filters are built into this, so you will need to add a bandpass filter for the WSPR band that you are using.
WSPR (Weak Signal Propagation Reporter) (pronounced "whisper") is an amateur radio digital HF mode designed to be decodable even if the signal is received with very low power. Because of this design, even low-power transmitters can be received from all over the world. It can also be used to help determine HF radio propagation conditions as WSPR reception reports are typically automatically uploaded to wsprnet.
If you are interested, Ihar has written about his project in more detail over on Reddit.
Over on the Tech Minds YouTube channel, Matt has uploaded a new review and demonstration of a Malahiteam DSP1 SDR Receiver 50KHz - 2GHz. This particular unit appears to be a Chinese clone unit which is actually called a 'Malahit SDR'. The Russian company Malahiteam makes the original units, and they come in a different enclosure and feature the full Malahiteam logo.
In the video Matt shows this version of the Malahit DSP1 in action, noting that the built-in speakers sound great and that RF performance seems to be good. He does however note that the enclosure is a bit cheap, being built out of PCB boards, and that the top encoder knob sometimes doesn't work properly. Overall Matt mentions that he probably wouldn't buy it at the current ~US$180 price point, noting that better newer models like the DSP2 and DSP3 already exist.
Earlier this year the KiwiSDR 2 became available for purchase and began shipping out to customers. The KiwiSDR 2 is an upgraded version of the original KiwiSDR with the main upgrades being an enhanced RF front end and the addition of a digital attenuator.
Over on the Tech Minds YouTube channel, Matt received his KiwiSDR 2 and uploaded a review and demonstration of the product. In the video, Matt shows the external ports of the KiwiSDR and discusses the differences between the KiwiSDR 2 and the original version. Matt goes on to show how to set up the KiwiSDR 2 and shows it receiving through it's web-based receiving software.
KiwiSDR is a 14-bit wideband RX-only HF software-defined radio created by John Seamons (ZL/KF6VO). The KiwiSDR has up to 32 MHz of bandwidth, so it can receive the entire 10 kHz - 30 MHz VLF/LF/MW/HF spectrum all at once. Other than the specifications, the main interesting feature about the KiwiSDR is that it is designed to be operated entirely as an online web-based SDR which is accessed over a network connection. Owners can optionally share their KiwiSDRs online with anyone who wants to access it, which also allows for interesting distributed applications, such as TDoA direction finding, which allows users to pinpoint the location of unknown HF transmissions such as numbers stations.
KiwiSDR 2 - A Standalone Software Defined HF Radio Receiver
Back in August 2023 we posted about the pre-announcement of the KiwiSDR 2, an upgraded version of the original KiwiSDR. Most of the upgrades are minor or due to some chips becoming EOL. The main upgrades are an enhanced RF front end and the addition of a digital attenuator. One change is also the manufacturing country. Instead of being manufactured in China, the KiwiSDR 2 is now manufactured in New Zealand.
The new KiwiSDR 2 can be purchased from kiwisdr.nz. Pricing is $648 NZD ($395 USD) for the full KiwiSDR 2 cape + Beaglebone and enclosure set. The cape by itself is also available for $484 NZD ($295 USD). Currently the second production run is selling, and a third production run is in progress.
Previously the original KiwiSDR sold for $299 USD. Considering inflation, component changes and additions, and the change to a more expensive country to manufacture in, the price increase seems reasonable.
KiwiSDR is a 14-bit wideband RX only HF software defined radio created by John Seamons (ZL/KF6VO). The KiwiSDR has up to 32 MHz of bandwidth, so it can receive the entire 10 kHz - 30 MHz VLF/LF/MW/HF spectrum all at once. Other than the specifications, the main interesting feature about the KiwiSDR is that it is designed to be operated entirely as an online web based SDR which is accessed over a network connection. Owners can optionally share their KiwiSDRs online with anyone who wants to access it, which also allows for interesting distributed applications, such as TDoA direction finding, which allows users to pinpoint the location of unknown HF transmissions such as numbers stations.
The design generates an oscillator signal using the Pico's Programmable IO. For AM/SSB it uses the PWM output pins to generate an RF envelope which gets mixed together with the oscillator using an analog multiplexor. A small microphone is also connected to the Pico for voice transmissions. The designer notes that the output power is far too low to be used on the air, but adding an output amplifier would help.
The Raspberry Pi Pico is a low cost microcontroller board, and we note it cannot run Linux like standard Raspberry Pi boards. This means that software like RpiTX cannot be used.
To install the Armbian Linux operating system Joseph used the instructions from i12bretro and installed OpenWebRX after. Then together with his RTL-SDR Blog V3 dongle he turned the device into a cheap dedicated WSPR (Weak Signal Propagation Reporter) monitor allowing him to free up his Raspberry Pi 3 which was used for the task previously.
IT9YBG's Android TV Box converted into a WSPR monitor with an RTL-SDR Blog V3 and OpenWebRX
In one of his videos from a few days ago Matt from the Tech Minds YouTube channel tests out OpenWebRX+, an unofficial fork of OpenWebRX. OpenWebRX is open source software which enables users to put software defined radios like RTL-SDRs on the internet, allowing people from all over the world to access the receiver if desired, or just letting yourself access it remotely if you want to keep it private.
OpenWebRX+ adds several additional decoders and features on top of the official version. In the video Matt demonstrates OpenWebRX+ running on a Raspberry Pi 4, with an SDRPlay RSPdx. He demonstrates the web GUI in action and shows decoding examples of the various decoders that OpenWebRX+ comes with.
