POLL: What do you want in a future low cost SDR?

We've decided to ask the community what sort of radio would be more popular for a ~$30 RX-only SDR. Note that thus far this is only a hypothetical SDR that does not yet have any designs. We are just feeling for what's most interesting to people and exploring for future ideas which may not even be feasible at this time.

As always with engineering, there is always a trade off. It is likely that any low cost SDR can only be wide band, with basic RF performance, narrowband with good RF performance, or expensive.

What is most important to you in a software defined radio?

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Wider bandwidth: Currently the RTL-SDR allows you to see up to 3.2 MHz of spectrum live. Higher bandwidth (10 MHz or more) would mean seeing more of the spectrum at once without needing to retune, faster whole spectrum scans and the ability to receive wideband signals.

RF Performance: The RTL-SDR has an 8-bit ADC. While sufficient for many applications, in the presence of strong signals the ADC will saturate resulting in poor reception and signal overload. Higher end SDRs like the SDRplay, Airspy, LimeSDR etc use 12-bit or higher ADCs.

Frequency Range: The RTL-SDR V3 can tune from 500 kHz to 1.75 GHz. An expanded SDR could potentially tune up to 4 GHz or even higher.

If you're interested in other things, please comment on this post!

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Decoding the Lucky-7 Cubesat

Lucky-7 is a Czech cubesat that carries some interesting sensors including a low power GPS receiver, a gamma ray spectrometer and dosimeter and a photo camera. The creators also claim that it is "probably the lowest-cost scientific space mission in human history". It was recently successfully launched and orbited together with the Meteor M2-2 weather satellite and several other small satellites.

"We did not build just another satellite. It is a flying laboratory. The satellite is going to test something that nobody has ever done before. Thanks to our background in electronics, materials and space effects, we implemented commonly used electrical parts from automotive and IoT industry in totally new ways. Gallium Nitride power transistors used in modern electric cars do not contain insulation layer to control its conductivity. That makes them much less vulnerable against the space radiation. We fly the world's first MOSFET-free power supply ever built for small satellites. The LED lighting industry has been used to make composite aluminum radiation shields for us. It is very cheap, lightweight and it naturally increases the mission lifetime," says Jaroslav Laifr, the CEO and founder.

If all goes well, the team will be able to measure the in-situ radiation background by miniature onboard Dosimeter and monitor the health of key subsystems, such as communication or data storage by complete satellite telemetry. The experimental Gamma Spectrometer payload informing about the energy of incident radiation will be able to detect Gamma Ray Bursts from distant galaxies. The platform also contains the VGA camera to demonstrate the data transfer capability. It may capture the first colour images ever taken by Czech satellite, possibly detecting the aurora glow. Such pictures would be greatly utilized for the outreach and inspire a new generation of scientists and engineers.

Daniel Estesvev has recently added a Lucky-7 decoder to gr-satellites, and has uploaded a post explaining some technical details on how he created the decoder. With this decoder, anyone with an SDR and appropriate antenna should be able to receive and decode the telemetry (no word on camera images yet). He writes that "Lucky-7 transmits 4k8 GFSK telemetry in the 70cm band. It uses a SiLabs Si4463 transceiver with a PN9 scrambler and a CRC-16. You must use FM mode to receive this satellite (437.525MHz)."

CubeSat companies like Sky Fox Labs are also tracking the satellite, and are tweeting results.

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SignalsEverywhere: Satcom Antennas for L-Band Reception via RTL-SDR + Podcast on the MiTee CubeSat Project

On this episode of SignalsEverywhere on YouTube Corrosive shows off several antennas that can be used for Inmarsat and Iridium satcom reception. His video shows off a commercial Inmarsat branded satlink antenna which is designed to be used on moving ships, a grid dish antenna, a custom QFH iridium antenna made from a repurposed Vaisala radiosonde, a commercial Iridium patch, an older Outernet/Othernet Iridium patch and a custom Iridium patch that Corrosive built himself.

Satcom Antennas for L-Band Reception via RTL SDR

A few days prior Corrosive also released a new episode of his podcast. In this episode he interviewed Derek a student from The University of Michigan who is working on the MiTee CubeSat. The MiTee cubesat is a small experimental satellite that will explore the use of miniaturized electrodynamic tethers for satellite propulsion.

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Dronesense: A LimeSDR Based Drone Detector and Jammer

Over on the LimeSDR CrowdSupply blog, Ogün Levent has submitted a short article about his "Dronesense" project. Dronsense is a spectrum-scanning and jamming system based on the LimeSDR. The LimeSDR is a US$299 12-bit TX/RX capable SDR that can tune between 100 kHz – 3.8 GHz, with a maximum bandwidth of up to 61.44 MHz.

Drone defense is a problem that is plaguing airports, cities, sensitive buildings and the military. These days anyone with a low cost off the shelf drone can cause havoc. Solutions so far have included net guns, drone deployed nets, wideband jammers, GPS spoofers, traditional and passive radar systems, visual camera detection, propeller noise detection, microwave lasers and SDR based point and shoot drone jamming guns like the IXI Dronekiller.

Both the expensive made for military IXI Dronekiller SDR gun, and the LimeSDR Dronesense work in a similar way. They begin by initially using their scanning feature to detect and find potential drone signals. If a drone signal is detected, it will emit a jamming signal on that particular frequency, resulting in the drone entering a fail-safe mode and either returning to base or immediately landing. Specifically targeting the drone's frequency should help make the jammers compliant with radio regulations as they won't jam other legitimate users at the same time. We note that this method might not stop drones using custom RF communications, or fully autonomous drones.

Dronesense: Drone Detection and Jammer Mounted on another Drone, running on a LimeSDR.
Dronesense: Drone Detection and Jammer Mounted on another Drone, running on a LimeSDR.

However, unlike the IXI Dronekiller gun, Dronesense requires no pointing and aiming of a gun like device. Instead it appears to be mounted on another drone, with an omnidirectional jamming antenna. It runs with a GNU Radio based flowgraph which decides if a detected signal is from a drone, and if so activates the jammer. Unfortunately the software and further details don't appear to be available due to non-disclosure agreements.

DroneSense Second Jamming Test (Software Defined Aerial Platform)

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SDR-Makerspace Talk: Evaluation of SDR boards and toolchains

The Software Defined Radio Academy YouTube channel recently uploaded an interesting talk by Alex Csete (creator of the popular GQRX and GPredict applications), and Sheila Christiansen. Their presentation discusses their work with the European Space Agency (ESA), Libre Space Foundation and how they are running SDR Makerspace's that are helping students create and track cubesats. During the talk Alex and Sheila also describe various SDR hardware, and how they test them for their purposes.

SDR Makerspace (https://sdrmaker.space) is a collaboration between the European Space Agency and Libre Space Foundation, with the objective of bringing innovative open-source SDR technologies to space communications.

Space is a complex environment. Attempting to incorporate SDRs into complex subsystems of space missions without sufficient understanding of the technology can add unnecessary risks and uncertainties to the mission. SDR Makerspace aims to bring open-source SDR technology to the space industry, focusing on the practical aspects of satellite communications, so as to reduce such risks.

Makers, open-source hackers, SDR enthusiasts, and researchers are collaborating on SDR hardware and software activities, focusing on rapid prototyping and development of reusable, open-source SDR components for future CubeSat missions.

The collaboration consists of many activities, which are organized into three main elements: development of reusable GNU Radio components, research and development in cutting edge technologies like AI/ML, and testing of SDR hardware and software.

Current activities are presented with a focus on the testing of the hardware and software. An overview of the investigation into the characteristics, such as, performance under realistic conditions, damage by radiation to essential parts, functionality of FPGA toolchains, the SDR-system’s complexity, and accessibility to the open-source community will also be covered.

Alex Csete, OZ9AEC: SDR-Makerspace: Evaluation of SDR boards and toolchains

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A Demonstration of RSPDuo Diversity Being used to Cancel Local Interference

SDRPlay have recently published a video demonstrating how the new RSPduo diversity feature in SDRUno can be used to cancel local interference.  The SDRplay RSPDuo is a 14-bit dual tuner software defined radio capable of tuning between 1 kHz - 2 GHz. It's defining feature is that it has two receivers in one radio, which should allow for interesting phase coherent applications such as diversity. The RSPDuo's diversity feature allows us to either combine two antenna signals together for an up to 3 dB increase, or for removal of an unwanted noise source via subtraction of signals.

In the video they show a broadcast AM signal that has it's SNR reduced by being on top of a local electrical noise source. The use a Bonito Mega-dipole on tuner 1, and a Bonito Mini-whip on tuner 2. The Mini-whip appears to receive the local interference stronger, so can be subtracted away from the Mega-dipole's signal with the diversity function. The result is improved SNR, and the noise is almost entirely cancelled.

There are 2 very practical applications for diversity software. The first is MRC (Maximum Ratio Combination) Diversity which, in order to be effective, needs two antennas presenting the same signal with some degree of diversity. Then there is this second impressive application which is becoming more and more useful due to the growing number of domestic sources of interference.

This is possible in an RSPduo, due to the coherent nature of the combined tuner streams being presented to the computer for processing.

Using Diversity in SDRplay's SDRuno to Cancel Local Interference

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Weather Satellite NOAA 15 Appears to have Failed (Again)

Back in April 2018 we posted how the NOAA-15 APT weather satellite that many RTL-SDR users enjoy receiving images from was having problems with it's scan motor resulting in image errors. The satellite recovered from that problem, but today the problem appears to be back and in a much worse way now.

Users on Reddit and Twitter have reported bad images coming in from NOAA 15. Over on Reddit u/rtlsdr_is_fun has provided a post showing an example of a corrupted image, and also provided an IQ and Audio file. On his blog [Karsey] has also posted some interesting looking corrupted images that he's received.

Corrupted NOAA-15 Image Received by [Karsey]
Corrupted NOAA-15 Image Received by [Karsey] (See his post for the full sized images)

NASA have put out a statement indicating that yet again it is a problem with the scan motor, and the problem could be permanent.

The NOAA-15 AVHRR Scan Motor current began showing signs of instability at approximately 0400Z on July 23, 2019. At about 0435Z the current rose sharply to about 302mA where it has remained. Scan motor temperature began rising about the same time and is currently steady at ~26M-0C. Black body temperatures dropped sharply at about the same time. The instrument appears to no longer be producing data.
This behavior is consistent with a scan motor stall, but requires further investigation. Options for recovery are limited.

Having been launched in 1998 with a minimum spec of 2 years operation, NOAA-15 has already well outlived it's time and may finally be failing for real. We hope it will recover, but if not we should be thankful that Russian weather satellite Meteor M2-2 is now fully operational and transmitting beautiful high resolution images.

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Atomic Radio: Quantum Laser Based Radio Reception

Software defined radio (SDR) is a relatively new technology that has impacted the world of radio technology in many ways. But beyond SDR, there are still some other very interesting radio technologies being worked on, such as "Atomic Radio" a.k.a "Quantum Radio".

Atomic radio is essentially an idea that makes use of how special "Rydberg" atoms can modulate a laser beam when radio waves pass through them. A photo diode is then used to optically detect the radio wave from the modulated laser. This way of receiving requires no traditional radio circuits like amplifiers, mixers, and of course no antenna, so in theory the radio signal could be received with significantly less noise and with the highest possible SNR.

If you're interested in learning more about Atomic Radio, Hackaday recently ran an excellent article where they describe the concept and science behind it in more depth. They also go into some recent studies where scientists showed that they were able to receive two signals at once, and mention how one paper describes an extremely wideband Atomic Radio that can receive from the C-Band to the Q-band (4 GHz to 50 GHz).

Hackaday's Article is a Great Introduction to Atomic Radio
Hackaday's Article is a Great Introduction to Atomic Radio
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