In this episode of Frugal Radio's ongoing SDR Guide videos Rob demonstrates how he uses Unitrunker and SDR Trunk with SDRs like an RTL-SDR to monitor Public Safety networks in his area. Rob writes:
This is a video demonstrating how I use UniTrunker and SDRTrunk with Software Defined Radios to monitor multiple Public Safety networks in my area.
There is some information on how trunked systems work, and you can hear how my SDRs produce better P25 audio on a Simulcast (LSM) system than some scanners.
I use a couple of RTL-SDR v3s and an Airspy R2 in this episode.
2020 SDR Guide Ep 6 : Trunk tracking Public Safety systems with UniTrunker and SDRTrunk
At this years ICNP 2020 IEEE conference a paper titled "Real-World ADS-B signal recognition based on Radio Frequency Fingerprinting" (pdf file) was presented by researchers from Harbin Engineering University in China. The idea presented in the paper is to use RF "fingerprinting" techniques to uniquely identify and confirm that the ADS-B signal originates from the correct aircraft source.
RF fingerprinting works on the premise that every transmitter has small manufacturing variances that result in slightly different signals be transmitted, resulting in a unique "fingerprint" that can be traced to a particular transmitter. The idea here is to use these fingerprints to ensure that a known aircraft is indeed transmitting an ADS-B signal and the signal is not being transmitted from a fake spoofer. ADS-B is completely unencrypted and not authenticated, so spoofing of ADS-B signals may be a real security threat.
In the teams research they use an RTL-SDR to collect ADS-B signals from five different aircraft. They then use that data to create "Contour Stellar Images" and train a deep learning neural network which after training accurately identifies which aircraft a signal comes from.
Thank you to a few users who have submitted links to u/ThePhotoChemist's Reddit post showing his e-ink display for his live GOES-16 weather satellite images. The post doesn't go into much detail about the setup, however it seems that he is using a Raspberry Pi, and displaying the images via a 9.7 inch E-Ink display which he notes does not come cheaply. He also notes that the resolution is quite low, and that it's limited to 16 shades of grey, however the images do still look good on it. The display is mounted into a picture frame which makes a very nice display piece.
If you're interested in receiving live GOES (or GK-2A) weather satellite images with an RTL-SDR we have a tutorial available here.
Thank you to Happysat for reviewing the QO-100 Bullseye LNB which we have available in our store, eBay and Aliexpress. The Bullseye LNB is an ultra stable TCXO (temperature compensated oscillator) based LNB which makes it very good at receiving the narrowband signals on the QO-100 amateur geostationary satellite.
Standard LNBs that are sometimes used for QO-100 are not designed for narrowband signals and hence do not have temperature compensated oscillator which can result in the signals drifting in frequency significantly as the ambient temperature fluctuates. Happysat also notes that the extra stability seems to have increased signal strength on the more wideband DATV reception as well.
First test's on Es-Hail Narrow SSB transponder compared to my old regular sat-tv LNB clearly is showing more signal stability overall.
It does need some time for both the tuner and LNB to get stable, but that's only a few minutes.
Weather conditions shows less "drifting" of the pll where the old LNB was very sensitive of temperature changes, clouds before the sun did have immediately effect on the signal stability.
Some days with storms reception was impossible on SSB Narrow band.
Winter is coming over here so it gets a lot colder and more storms, but I don't expect any problems with this LNB.
Wideband testing DATV reception also shows a more stable signal although its a wider signal then narrowband, it also did increase the signal, e.g. a signal lock happens much faster.
More information about Happysat's setup and his use of the Bullseye QO-100 LNB can be found on his QO-100 website.
Over on his channel popular electronics YouTuber Andrea Spiess has uploaded a tutorial video showing how to properly use a NanoVNA V2. The NanoVNA V2 is a vector network analyzer which can be used to measure and tune things like antennas, filters and cables. In the video Andreas aims to explain the differences between the VNA, Spectrum Analyzer and VSWR meter, what you can measure with a VNA, how to read the VNA results, the limitations of cheap VNAs, why and how to calibrate, and a review of the overall quality.
Andreas explains these concepts in a very easy to understand way, so this video is a great start if you've ordered a NanoVNA.
#359 How to properly use a NanoVNA V2 Vector Network Analyzer & Smith Chart (Tutorial)
Thank you to a few readers for suggesting a post about the "tinySA". The tinySA is a low cost standalone spectrum analyzer which was made recently available from Chinese manufacturer "Hugen" who was the manufacturer that popularized the original NanoVNA. It can be found on Aliexpress for about $49 shipped worldwide. R&L also have US based stock available. The official specs from tinysa.org/wiki read:
Spectrum Analyzer with two inputs, high quality MF/HF/VHF input for 0.1MHZ-350MHz, lesser quality UHF input for 240MHz-960MHz.
Switchable resolution bandpass filters for both ranges between 2.6kHz and 640kHz
Color display showing 290 scan points covering up to the full low or high frequency range.
Input Step attenuator from 0dB to 31dB for the MF/HF/VHF input.
When not used as Spectrum Analyzer it can be used as Signal Generator, MF/HF/VHF sinus output between 0.1MHZ-350MHz, UHF square wave output between 240MHz-960MHz.
A built-in calibration signal generator that is used for automatic self test and low input calibration.
Connected to a PC via USB it becomes a PC controlled Spectrum Analyzer
Rechargeable battery allowing a minimum of at least 2 hours portable use
A spectrum analyzer allows you to view a defined slice of the frequency spectrum on a graph. It does not allow for demodulation of signals. We note that SDRs like the RTL-SDR could be used as a spectrum analyzer too with software like QSpectrumAnalzyer and Spektrum, however the advantage of the tinySA is that it is a standalone package with it's own screen that can easily be used in the field. Unlike an SDR extra computing devices like a computer or smartphone are not required.
Over on YouTube IMSAI Guy has been uploading a few videos reviewing the tinySA. From his videos he found a few issues including a slow update rate, harmonics and high phase noise. However, later he finds that most of the harmonic issues disappear as long as the input signal level is kept below -30dBm. In some more recent videos he also finds a fault with the attenuator chip on one of his tinySA units and repairs it by replacing the chip.
The course appears to be intended for University teachers in order to accelerate adoption of SDR based teaching of RF courses. We're unsure if this material will be released to the general public as their signup form appears to ask for University details. They write:
Alton, England; 5th November 2020 – SDRplay Limited announces a new Radio Communications course for under-graduate teaching as part of its SDRplay Educators Programme
“Understanding Radio Communications – using SDRs” includes a rich set of teaching materials and practical exercises to help students understand the key elements of radio communications. This one semester course provides teaching materials and practical workshops that lead students from the first switch-on of a Software Defined Radio (SDR), through to signal reception, demodulation, and finally, successful communications with satellite signals.
As well as guides and set-up instructions for teachers for both the lecture and lab sessions, there are downloadable teaching materials in both PowerPoint and .pdf formats. There are video guides showing the lab activities and there’s a dedicated new forum for teachers to share experiences and to get help from the authors.
The course was created in association with academic partners Sapienza University of Rome, Department of Mechanical and Aerospace Engineering whose intention was to create a practical course that will inspire Science, Technology and Engineering students to nurture their understanding of radio communications.
The course started life as a 12-hour optional course for third-year bachelor students in Aerospace Engineering and has been broadened to make it suitable for all students that have some basic knowledge of signal theory and signal processing. It can either be run as an additional or optional “module” or adapted to be included as materials within a full year radio communications subject.
Robert Owen, University Programme specialist at Essaimage who guided the academic team, says, “I have spent 26 years in global “University Programmes” and across this time I’ve learned two fundamental principles. The first is that teaching materials must fill an essential need in the curriculum, not just be something that business thinks should be taught. And secondly, that the best teaching materials come from academics not commercial trainers. This course, Understanding Radio Communications, fulfils these principles generously, and I am proud to be associated with it!”
Key dates:19th November 2020, 1300 UTC – SDRplay and Course developers, Lorenzo Frezza and Paolo Marzioli from the Department of Mechanical and Aerospace Engineering, (DIMA), Sapienza University of Rome, will host a webinar presenting the programme and taking questions via YouTube chat.
About the SDRplay Educators Program The SDRplay Educators Program provides practical encouragement to teachers around the world so that they can use SDRplay’s SDR receivers in courses and student projects. The focus is on providing the key elements needed to teach a course: a suitable hardware platform at a reasonable price, ready access to SDRplay software, effective technical support, and excellent teaching materials that serve genuine teaching needs. The SDRplay Educators Programme is open to all members of academia, see
Evariste (F5OEO) has just announced the release of an update to RPiTX which allows it to now be used on a Raspberry Pi 4. If you are unfamiliar with it, RPiTX is a program for Raspberry Pi single board computers that allows you to transmit almost any type of signal on frequencies between 5 KHz up to 1500 MHz with nothing more than a piece of wire connected to a GPIO pin. Evariste also notes that the new version is compatible with the beta 64-bit version of Raspbian.
Some examples of signals you can transmit with RPiTX include a simple carrier, chirp, a spectrum waterfall image, broadcast FM with RDS, SSB, SSTV, Pocsag, Freedv and Opera. You can also use an RTL-SDR to record a signal, and replay the IQ file with RPiTX. However, please remember that transmitting with RPiTX you must ensure that your transmission is legal, and appropriately filtered.
