Category: Other

DragonOS: Now with RF Propagation and Calculation Tool

DragonOS is a ready to use Ubuntu Linux image that comes preinstalled with multiple SDR software packages. In the recent R14 Preview update, Aaron, the creator of DragonOS has added a new very useful RF propagation and calculation tool. The tool works in conjunction with elevation data to calculate the theoretical signal propagation of a transmitter.

The tool is provided by the open source Signal Server software package, which is based on the original SPLAT! software by John Magliacane (KD2BD). Aaron has also provided a video that demonstrates the software in action, shows how to use it, and explains his future plans for making it easier to use.

This video is a preview of a new RF Propagation and Calculation feature provided by Signal Server. Additionally, custom web server scripts by Dr. Bill Walker, will also be included in DragonOS Focal R14 in the near future. There's a lot of moving parts, but once complete, all you "should" have to do is download, convert, and place the SRTM elevation data for the areas needing coverage calculations in the /usr/src/SDF directory. In the meantime, I'd recommend reading up on all the below material. I've been reading a lot and still don't understand it all!

DragonOS Focal R14 Preview w/ Signal Server + RF Propagation Web Server (SPLAT!, Dr. Bill Walker)

Scikit-RF: An Open Source RF Engineering Package in Python

Thank you to Alexander, the original author of scikit-rf (aka skrf) for writing in and sharing his project which he believes may be of interest to some readers. Scikit-rf is an open source, BSD-licensed RF/Microwave engineering package implemented in Python. The package can be used for simulating various RF components such as transmission lines and waveguides, as well as creating models from data measured from real components which can then be used in a simulated system.

As an example, Alexander shows how you can plot Touchstone data on a Smith chart in 3 Python lines.

    > import skrf as rf
    > ntwk = rf.Network('ring slot.s2p')
    > ntwk.plot_s_smith()
 

Alexander also writes:

With skrf you can also do all your own calibrations offline, time gate when you feel like it, connect and manipulate microwave networks and plot all the results. And... you can read all the source code!, which is really important for proto-typing and research. Check out the Documentation or Examples for a more in-depth look at scikit-rf.

Here are a couple links to projects using scikit-rf

History 

scikit-rf was created in 2009 by Alex Arsenovic while he was a graduate student at the University of Virginia’s millimeter wave research lab in 2009. scikit-rf is licensed under the BSD License and is currently being actively developed by a group of volunteers on Github.

 

PiccoloSDR: A Simple SDR From a Raspberry Pi Pico

The Raspberry Pi Pico is a $4 microcontroller board. Recently radio amateur Luigi Cruz discovered that the ADC on the Pico could be used as a simple direct sampling software defined radio, with a bandwidth of 250 kHz. The idea is that the ADC data is made available to a PC connected to it's USB port via emulated TCP/IP protocol. On the PC side, GNU Radio is then used to process the received ADC data, turning it into an SDR.

Applications of a direct sampling SDR with only 250 kHz are limited, as it's only possible to receive up to the LF band, and there are not many signals that low in frequency. However, it is an interesting project that can be used to demonstrate a simple SDR. If you're interested in trying it out, the code is available over on GitHub.

PiccoloSDR Project - Using the Raspberry Pi Pico RP2040 as an SDR - First Test with GNU Radio.

[Also seen on Hackaday]

Army Builds Wideband DC to 20 GHz Quantum Receiver

Back in July 2019 we posted about a new development in radio technology known as "Atomic Radio" or "Quantum Radio". In that post we discussed an article that explained the concept and science behind the idea and noted how some researchers described the possibility of a very wideband capable receiver.  

Recently the US Army has described how they built a quantum radio that can receive from DC to 20 GHz. If you're interested in the science, the paper is published in the Journal of Physics B: Atomic, Molecular and Optical Physics and it is available on sci-hub. The radio uses something called a Rydberg sensor which they describe below. 

The Rydberg sensor uses laser beams to create highly-excited Rydberg atoms directly above a microwave circuit, to boost and hone in on the portion of the spectrum being measured. The Rydberg atoms are sensitive to the circuit's voltage, enabling the device to be used as a sensitive probe for the wide range of signals in the RF spectrum.

Army researcher Kevin Cox notes how this is the first implementation that can operate over such a wide frequency range:

"All previous demonstrations of Rydberg atomic sensors have only been able to sense small and specific regions of the RF spectrum, but our sensor now operates continuously over a wide frequency range for the first time," said Dr. Kevin Cox, a researcher at the U.S. Army Combat Capabilities Development Command, now known as DEVCOM, Army Research Laboratory. "This is a really important step toward proving that quantum sensors can provide a new, and dominant, set of capabilities for our Soldiers, who are operating in an increasingly complex electro-magnetic battlespace."

Quantum radios may be one of the next big leaps in radio technology. However as they require lasers and the space of a small laboratory the technology will probably be restricted to the military and institutions for the time being.

A Rydberg sensor setup (LEFT), The experimental setup for a Rydberg Quantum Radio Receiver (RIGHT)

RF Power Snitch: RF Power Measurement Companion for Protecting RF Equipment

Thank you to Majodi Ploegmakers who wrote in and wanted to share a product he's created that might be useful for some RF enthusiasts. The product is called the "RF Power Snitch", and is a tool used to quickly measure RF input power to determine if input power from a signal source is too strong and could damage measurement equipment such as an SDR or NanoVNA. The product is not yet for sale, but Majodi has an availability notification signup page.

NickStick Design Announces - RF Power Snitch –
“Your RF Measurement Companion”

The Netherlands: Today, NickStick Design, an electronics design company for Makers, announced their RF Power Snitch. After a successful launch of SwarmDrive through Crowd Supply last year, NickStick Design went on and designed another useful tool for makers in the RF (Radio Frequency) domain this time.

Of the company’s recent crowd funding campaign, Majodi said, “We were very pleased with the interest our last, somewhat niche, product received. It spurred us on to develop and realize our next idea”.

Today, the RF domain has become accessible to everyone through affordable tools that many could only dream of before. The only tool missing though, is a simple device for checking the, potential, destructive power of the signals one would want to analyze. Because, although tools like the TinySA, NanoVNA or SDR devices are extremely affordable today, for a maker it is still an investment worth protecting.

That’s why our goal was to develop a low-cost companion device that can help makers and experimenters (especially beginners) in the RF domain to gain insight in the power levels of a signal before hooking things up to their valuable test equipment. As an extra to this we also made it possible to attach an MCU for doing power readings and plotting.

Website: https://powersnitch.nickstick.nl

The RF Power Snitch
The RF Power Snitch

TinySDR: An OpenSource SDR for IoT Applications

We recently came across a relatively new SDR design that is called "TinySDR". The design is entirely open source and is focused on helping analyze wireless Internet of Things (IoT) applications. Currently the device is not manufactured and sold by anyone, but the open source Altium Designer PCB files, BOM and firmware can be found on their GitHub.

Over on hackster.io Tom Fleet has also given the TinySDR a writeup. He notes that the design is based around the AT86RF215 transceiver chip and a Lattice Semiconductor ECP5 FPGA. The board is split into an input for 2.4 GHz and a sub-GHz input. On the GitHub there are currently demo files available to turn the SDR into LoRa and FSK modulators.

The TinySDR

Arecibo Radio Telescope Collapses: A look back at some SDR fun with Arecibo

The Arecibo Radio Telescope has collapsed. Once the largest single dish radio telescope in the world at 305m, Arecibo was mostly used for radio astronomy research. However, the dish was made famous in 1974 for deliberating beaming a message into space as part of a search for extraterrestrial intelligence (SETI) experiment. It also played a part in popular culture, being a part of several famous films such as Golden Eye and Contact.

As part of it's goodbye we thought we'd highlight a few old posts where Arecibo was used together with SDRs for some interesting applications.

Back in 2014 we saw engineers hook up USRP software defined radios to Arecibo in order to contact the lost ISEE-3 NASA spacecraft (Wikipedia Article). The idea was to contact the solar orbiting spacecraft which was last heard from in 2008, and get it to fire it's thrusters in order to reuse it for a new mission. The idea was initially abandoned by NASA, however a crowdfunding campaign raised US$125,000 which funded the project.

The project required finding and researching the original spacecraft documentation, and implementing the modulators and demodulators in GNU Radio. Whilst being successful in communicating with the satellite, ultimately the project failed due to the satellite's nitrogen tanks which had long leaked empty. But the fact that they were even able to find and communicate with the spacecraft using Arecibo was a major achievement. If you're interested in that project, Balint's 2015 talk on YouTube is an interesting watch. 

Later in 2017 we saw how Arecibo was used for an Ionospheric heating experiment which involved transmitting 600kW of net power into the Ionosphere. This resulted in SDR users around the world being able to receive the signal. Other posts involve u/moslers Reddit post where he toured Arecibo and showed how they used a familiar program, HDSDR, as part of their monitoring suite.

So goodbye to Arecibo. However, we can look forward to the 500 meter Chinese FAST (Five-hundred-meter Aperture Spherical Radio Telescope) giving us new opportunities for single dish radio observations in the future.

Arecibo Radio Observatory

Etherify 4: Using PC Ethernet RF Leakage to Transmit QRSS CW

Recently we've posted about Etherify a few times, mostly about how the unintentional RF leakage from the Raspberry Pi 4 Ethernet hardware is really strong and can be modulated to transmit data. In one of his latest posts Jacek Lipkowski (SQ5BPF) explores if Ethernet ports on PC's exhibit any sort of RF leakage too, and if it can be modulated into a data signal.

The answer is yes, there is some RF leakage, however unlike the Pi 4 the speed at which the leakage can be modulated is much slower, and also the signal strength is much lower. Despite the slow modulation speed, Jacek was still able to transmit data by using QRSS CW, which is essentially just very slow morse code. Using this idea he was able to transmit, and receive the CW signal with an RTL-SDR over a distance of 3 meters at 375 MHz, 625 MHz and 250 MHz. The signal strength is nothing like the Pi 4's Ethernet RF leakage which can be received strongly from over 50 meters away however.

Etherify: Transmitting QRSS CW via Ethernet RF leakage from PC to PC