Over on YouTube user Petr Horký has uploaded a helpful tutorial video showing how to install GNU Radio on Windows 10. Petr goes through the steps from installing Python, pip and other dependencies like numpy and pyqt, to installing GNU Radio itself and then ensuring that the system PATH is set correctly.
GNU Radio is a block based programming language for building digital signal processing applications (e.g. demodulators/decoders). It is very useful for experimenting with more advanced SDR concepts, and there are also many RTL-SDR compatible applications built with GNU Radio as well. GNU Radio is typically run on Linux, but can also run on Windows now too, although perhaps not every program will be compatible.
How to install GNU Radio Companion on Windows 10 (pip, environment variables)
Recently JJ wrote in and wanted to share his multi-feature living room radio that he's created with a Raspberry Pi, RTL-SDR, and various software packages installed on the Pi. Previously we posted about his cute LegoPi radio, and this living room radio is an iteration on that.
The radio is able to tune into live broadcast FM via an RTL-SDR and the NGSoftFM software, and also can be remotely access with SpyServer. It can also tune into internet radio, or play MP3 files. He's also installed Google Assistant and Alexa onto the Pi, so it can work as a digital assistant too. The features and software he uses are noted below:
FM / DAB+ / Internet radio with random mode / MP3 player / Google assistant / Amazon Alexa / SPYserver (SDRsharp), all controlled with a USB keypad or a Bluetooth remote control.
Internet radio VLC (https://www.videolan.org/vlc/index.html) The random internet radio part is a lot of fun to use. You can do random by genre or just random everything. Reminds me when turning the MW dial at night when I was a kid and not knowing what was coming next! It is just a python script that fetch the icecast directory then populate a small SQL database on the pi. I used this (https://github.com/ksc91u/icecast_play) as a starting point.
MP3 player VLC. I used a 16GB SD card on the pi (good compromise between speed of boot versus capacity). The whole system takes a little bit less than 5GB, which means I have 10GB+ for MP3 files.
SPYserver More a gadget than a serious tool because I'm using a wire for antenna (on the last radio) but has proven to be usefull to help position the wire for optimum FM / DAB+ reception by looking at the spectrum and play with the dongle gain in SDRsharp (https://airspy.com/spy-servers/).
Bluetooth remote control I used a PlayStation 3 (PS3) bluetooth remote since the pi 3 has bluetooth built-in. Easily available in used video game stores and very cheap, the remote works very well but it took me a while to get it going. This page helped: https://www.mythtv.org/wiki/Sony_PS3_BD_Remote
Last but not least, the radio is a complete Linux environment so I can connect to it from my Win10 box via SSH (https://www.chiark.greenend.org.uk/~sgtatham/putty/latest.html) and play with all the RTL-SDR goodies, even GNU Radio :-) providing you install a desktop environment (for ex. PIXEL) on top of Raspbian Stretch Lite.
For a while now researchers at MIT and several other universities have been investigating methods for using frequencies in the WiFi bands to see through walls using a form of low power radar. The basic concept is to track and process the reflections of these signals from peoples bodies.
Recently researchers at MIT have taken this idea a step further, combining the radar results with machine learning in a project they call RF-Pose. The result is the ability to recreate and track full human post information through walls. The abstract from their paper reads:
This paper demonstrates accurate human pose estimation through walls and occlusions. We leverage the fact that wireless signals in the WiFi frequencies traverse walls and reflect off the human body. We introduce a deep neural network approach that parses such radio signals to estimate 2D poses. Since humans cannot annotate radio signals, we use state-of-the-art vision model to provide cross-modal supervision.
Specifically, during training the system uses synchronized wireless and visual inputs, extracts pose information from the visual stream, and uses it to guide the training process. Once trained, the network uses only the wireless signal for pose estimation. We show that, when tested on visible scenes, the radio-based system is almost as accurate as the vision-based system used to train it. Yet, unlike vision-based pose estimation, the radio-based system can estimate 2D poses through walls despite never trained on such scenarios.
The hope is that this technology could one day be used as a replacement for camera based computer vision. It would be a non-intrusive method for applications like gaming, monitoring the elderly for falls, motion capture during film making without the need for suits and of course for gathering data on peoples movements.
It is not mentioned in the paper, but it is likely that they are using some sort of SDR like a USRP for receiving the signals. It's possible that a lower resolution system could be set up cheaply with a HackRF and some passive radar software.
RF Pose Estimating Human Pose Behind walls using RF signals in the WiFi frequencies.Multiple people tracked with RF-Pose
Over on YouTube the Ham Radio 2.0 channel has recently uploaded a talk that Scotty Cowling (WA2DFI) did at the 2018 TAPR digital communications conference. His talk centers around single board computers and his findings on the nine best single board computers (SBC) for ham radio SDR setups.
Scotty's talk begins by discussing why you'd want to use SBCs in your ham radio SDR setup, and explains why you might want to place them with the SDR close to the antenna, and then distribute the data over ethernet cable. He then reviews 9 boards listed below:
Hardkernel Odroid C1
Raspberry Pi 3B
Hardkernel Odroid XU4
ASUS Tinker S
FriendlyElec NanoPC-T4
Pine64 RockPro64
96 Boards Mediatek X20
96 Boards HiKey 960
UDOO X86 Ultra
The boards are compared against CPU clock speeds, architecture, cache, debut year, RAM, boot ROM, bus speeds, OS support, and more. Scotty also discusses the need for low latency operation, but is yet to compare this on the boards. The best value for money boards that Scotty recommends end up being the Odroid XU4, Tinkerboard, NanoPC-T4 and the RockPro64.
Ham Radio 2.0: Episode 151 - Evaluating 9 of the Best Single Board Computers for Modern SDR Systems
Over on YouTube user aonomus has uploaded a video showing how he's used an RTL-SDR to observe and listen to the radio signal generated via a chemistry lab's nuclear magnetic resonance machine. To do this he simply taps the RF output of the NMR machine which allows the RTL-SDR to listen to the signal and play it as audio. In the video he shows the sound of a sample of chloroform in acetone-d6. The demo has no real scientific purpose other than to hear the sound of the molecule. Normally the RF output goes straight into a spectrum analyzer for visual analysis.
Nuclear magnetic resonance is a technique used in chemistry for the analysis of chemicals, as well as in MRI medical imaging machines. Very basically, it works by applying a chemical sample to a strong magnetic field, exciting it with a strong pulse of RF, and listening to the echo. An echo will only occur when the radio waves are transmitted at the chemicals resonant frequency. The frequencies used are typically between 60 to 800 MHz.
A few years ago I came up with a demonstration for some high school students interested in chemistry. This demo is a modern take on a classic NMR experiment, using a low cost software defined radio to observe the FID signal as audio. In short, this demo allows you to hear the proton FID echo from the liquid sample inside the NMR magnet.
Nuclear Magnetic Resonance Demonstration Using Software Defined Radio
Othernet (formerly known as Outernet) are a providers of a free data service broadcast from satellites. They hope to build a system and low cost satellite receiver products where people can easily stream free daily data such as news, videos, books, and live audio down to a computer or phone from anywhere in the world via a device called a Lantern. It is a one way download only service, but may be useful for those in areas with limited internet, disaster preppers, or people in countries with internet censorship. The describe their mission as:
Othernet's mission is to build a universal information service; a truly pervasive multi-media service that operates in the most remote places and functions even when nothing else does.
In the past they ran a trial service on L-band satellite frequencies and used RTL-SDR dongles as the receiver. They have since discontinued that service in favor of a new Ku-band LoRa based service which can provide much more data - up to 200MB a day. The update released today was sent to Lantern backers, which was the receiver they crowdfunded for in their Kickstarter back in 2014. The update notes that the final iteration of the Lantern is close to being ready.
Broadcasting Khan Academy 24/7
Hello Backers,
Yes, we are still here. It’s been a long while since the last update, but that does not mean we have stopped–or even slowed–working on Lantern. We have been making progress, though it has been much, much slower than what everyone wants. Fortunately, we are in the final stage of development.
The last update described the new network technology we had developed. Our original goal was to broadcast 20 MB of content per day, which is what we were doing with our previous network. The new system is operating at 10-times that speed, which is a little over 20kbps and 200 MB of content per day. Some of the work we’ve been doing over the past few months is related to tripling our current download speeds. Our target is 60kbps, which results in over 600 MB per day. The size of the device will be similar to a standard flashlight.
At our current download speed of 20kbps, we are broadcasting both data and a 24/7 audio stream. I know many of you were interested in the educational applications that were highlighted during the campaign, which is why I’m very pleased to share that we are currently broadcasting the entirety of Khan Academy as a 24/7 audio stream. The Khan Academy library consists of over 900 separate lectures, which we’ve turned into a giant audio playlist. Now we just need to get Lanterns into everyone’s hands.
The next update will include a picture of our final antenna design. The antenna that is currently included in our DIY kit is 2-inches/5-cm across and the shape of a cone. We are trying to flatten the cone and also increase the size to about 4-inches/10-cm, which is what allows for greater download speeds. Since we are operating at microwave frequencies (12 GHz), both the design of the antenna and the parts to convert the high frequency to a lower one are pretty tricky. Microwave engineering is widely considered black magic, which is the main reason for the long break since the last update. We are close to turning the corner and are targeting the end of the year for our initial production run.
Unrelated to our technical work is our recent name change. We had been fighting a trademark issue for the past four years. We recently decided that it made more financial sense to change our name, rather than continue spending legal fees to defend our position. We are now Othernet (http://othernet.is). This name change does not mean we are going away, nor does it mean we are not delivering Lanterns. It’s just a legal hiccup.
Thanks for your patience and support while we get through the final stage of building what you all backed several years ago. I know it’s been a long time and we are making every possible effort to deliver something that exceeds everyone’s original expectations. Although it’s taking three times longer to develop and ship the product, what we now have will be ten-times more useful.
Over on Hackaday and Hackaday.io we've seen an interesting project by David Scholten called "Grid-2-Audio". The project's goal is to build a safe device for monitoring the mains electrical grid waveform via a power jack and PC soundcard. This is essentially an SDR, with the soundcard acting as the ADC for the 50Hz grid signal, and Grid-2-Audio acting as a safety isolator and signal preconditioner. About why you might want to monitor the mains power signal, David writes:
There is a lot to be observed from the waveform of the electrical mains. Harmonics, transient changes, periodic fluctuations, frequency shifts, impedance, power line communications - These all give clues as to the state of the country's electrical transmission system (or what loads your neighbour has connected). Platforms like MATLAB allow for the easy analysis of waveforms through powerful software tools, but only once the signal has been acquired.
The final product will be a black box with mains plug and a 3.5mm audio jack ready to plug into your soundcard. In order to make the device safe, mains isolation transformers are used as well as good PCB design practices that isolate live and safe areas on the PCB. In the design care is also taken to maintain signal integrity and to not introduce noise by ensuring that the power supply draws minimal sinusoidal current, and is in phase with the voltage.
In his tests he's been creating 100bit/s 2FSK test frames, transmitting them at 7.177 MHz, and receiving and decoding them on another PC with a hardware radio. The results show that the transmission is working perfectly, with only minor artefacts caused by RPiTX. Rowetel also notes that the narrow band spectral purity of the RPiTX output is remarkably clean. The only worry is the wide band harmonics which can easily be removed with filtering.
This shows that RPiTX could easily be used as a transmitter for amateur radio purposes, assuming proper external filtering is applied. Rowetel also mentions that he hopes that cheap radio technologies like RPiTX could one day be used to help reduce the cost and difficulty in covering the 'last 100 miles' of communications in the developing world.
RPiTX 2FSK apectrum analyzer measurement showing good narrow band spectral purity.
