Matt from the Tech Minds YouTube channel has recently uploaded a video highlighting 10 common mistakes made with software defined radio. The topics go over software choices, driver installation, coax choices, signal bandwidth, time of day, modulation type, high gain settings, low gain settings, cheap & cloned SDRs and finally antennas. This is a great video to watch if you are new to SDRs and radio in general.
A new set of beginners tutorials for the GNU Radio platform have been released on the GNU Radio Wiki. GNU Radio is an open source development toolkit for signals processing and is commonly used to build software demodulators and decoders for Software Defined Radios including the RTL-SDR.
The tutorials lead you through topics such as understanding flowgraphs, creating custom Python blocks, using DSP blocks, GNU Radio core mechanics, modulation and demodulation and more.
We are pleased to announce a new set of beginner-level tutorials, as well as a new tutorials landing page, you can check them out here
A big thank you to NumFOCUS for sponsoring the work and to Matt from wavewalkerdsp who did the bulk of the work!
These beginner-level tutorials walk a new user through starting GRC and creating a simple flowgraph, all the way up to creating custom blocks and using tags and message passing.
We would like to create follow-up tutorials that the GNU Radio community needs so please leave feedback in the Discuss tab of the main Tutorials page, here are some suggestions:
- Do you have ideas for future tutorials you’d like to see made?
- What doesn’t make sense in GNU Radio, or what is hard to understand?
- Where are the sticking points? What is hard to remember?
- What is hard to use?
- Are there any points in the current tutorials you’d like to see in more detail?
- What would you change about the tutorials?
You can also access the tutorials using the Tutorials link on the left hand sidebar of the GNU Radio wiki, from any page.
If you're interested in these tutorials you might also want to check out Michael Ossmann's set of video tutorials for the HackRF, which features GNU Radio usage heavily.
SDR++ is a general purpose receiver program compatible with almost any software defined radio including the RTL-SDR. Recent developments have seen the author release a beta of "SDR++ server" which is a program that allows users to access SDRs remotely, by connecting to them over a network connection. This is similar to existing server applications like rtl_tcp and Spyserver, however like SDR++ itself, SDR++ Server is compatible with almost any SDR and that is a major drawcard.
Today I'm happy to release the beta version of SDR++ Server! It works with all devices SDR++ supports. Since it's beta it's still missing compression and VFO+FFT mode.
— Whatsthegeek 🐲 (@ryzerth) January 22, 2022
As a demo, here is a LimeSDR being streamed over WiFi at 16MS/s
Get it here: https://t.co/DqvgHMZmm9#SDR #SDRPP pic.twitter.com/116JftzEOy
The server is still in development and the author notes that he is still working on adding new features like lossless compression techniques in order to reduce network bandwidth requirements. However, it has already seen to be running well in tests with a remote server positioned half way around the world, even without compression enabled.
Started working on adding lossless compression to SDR++ server. How well it works depends on what signals you're looking at and what SDR you're using. What I'm seeing with general purpose compression tables is 1.1 to 2.5 times compression (usually 1.5+). Custom tables should help pic.twitter.com/a1WRvxmdDs
— Whatsthegeek 🐲 (@ryzerth) January 24, 2022
We note that SDR++ author 'Ryzerth' has a Patreon. If you like seeing these SDR++ developments please consider support him.
Thank you to "Double A" for submitting his video that shows how to install and run the RTL-SDR compatible HD Radio decoder nrsc5-gui on a Windows machine. We've posted about nrsc5-gui and the modified nrsc5-dui software in the past, however despite being Windows compatible, it has only been simple to run on Linux.
In his video Double A shows us how to download and extract the files, how to set up the Windows mingw environment which is required to run the software, and where to place a required dll file dependency. Finally he demonstrates the software in action, running on his Windows machine.
The KK5JY Loop on Ground (LoG) antenna is a 15 feet per side square loop designed for reception of HF and lower. It simply consists of an isolation transformer and wire that as the name implies is placed somewhere on the ground in a square loop like shape. It is cheap and easy to build and compact in that it does not take up any usable space.
In his latest video Rob from the Frugal Radio YouTube channel tests out this antenna with his Airspy HF+ Discovery SDR. He uses a bit of wire lying around, and a low cost 9:1 Balun from NooElec as the isolation transformer. With this antenna he was able to pick up signals in the USA and all the way over to Australia from his home in Canada. NDB signals were also receivable.
At his childhood home Maxwell Dulin discovered that his garage door was controlled by a 30 year old system called the "Sears Craftsman 139.53708 Garage Door Remote". Being interested in SDRs Maxwell decided to see if he could reverse engineer the remote using his HackRF.
His first steps were to search for the frequency which he found active at 390 MHz. He then moved on to analyzing the signal with Inspectrum, discovering the OOK modulation, then working his way towards the binary control strings. One thing that helped with his reverse engineering was the use of the 9-bit DIP switches on the remote that configure the security code that opens up a specific door as this allowed him to control the transmitted bits, and determine which bits were used for the security code. With this and a bit of GNU Radio code he was able to recreate the signal and transmit it with his HackRF.
Finally Maxwell wanted to see how vulnerable this door is to a brute force attack that simply transmits every possible security code. Through some calculations, he discovered that brute forcing every possible security code in the 9-bit search space would only take 104 minutes to open any garage using this opener.
Remoticon 2021 was an online conference held in November 2021 and videos of presentations have recently been uploaded to the Hackaday YouTube channel this month. One very interesting talk was the presentation by Hash Salehi (RECESSIM) on reverse engineering electricity smart meters that are used to remotely monitor and bill home electricity usage in some neighborhoods.
In the past we've posted about Hash (RECESSIM)'s series on smart meter hacking a few times before. In this latest talk Hash summarizes his smart meter hacking experience, talking about how he went from reverse engineering the firmware, to using an SDR to capture and decode information from all the smart meters in his neighborhood, and finally to determining how to actually transmit data to his own smart meter network.
Hackaday have also posted a full writeup on his talk. This is a very in depth reverse engineering project so it is a great talk to learn from.
Job Genheniau's projects have been featured several times on this blog in the past for imaging the Milkyway and other astronomical objects like supernova's and protostar regions with a 1.8m radiotelescope dish and RTL-SDR or similar SDR.
In his latest achievement Job has noted that he has had some limited success in observing NML Cygni with his dish and an Airspy Mini SDR. NML Cygni is a 'red hypergiant' star situated within the Cygnus constellation, and it is one of the largest stars by radius known. Prior observations have found that it exhibits a spectral line at 1612.231 MHz.
Job's setup consists of his 1.5m dish (extended to 1.8m with mesh) on a rotor, a custom feed tuned for 1612 MHz, a 0.47dB NF low noise amplifier, an RF filter and an Airspy Mini SDR. Observations were made in SDR# and plotted with Excel.
The NML Cygni hypergiant is difficult for amateur's to observe, and Job notes that he is not aware of anyone previously observing it with a 1.8m dish. He notes that he had 20 failed attempts, but 5 recordings that stood out as possible successes.
However, ultimately Job has been unable to claim that the star was successfully observed, but his results to appear to show some possible success. He notes that some of the uncertainty stems from the fact that on some recordings he observed the peak at the expected -25 km's blueshift expected from the star, however other recordings had the peak at the wrong blueshift.
Job's full report on his observations can be found in this PDF document.
