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.
While we usually don't encourage politics on this blog, with the possibility of a Ukraine invasion by Russia we just wanted to issue a general warning to Ukrainian SDR owners. Last year we saw Stanislav Stetsenko a resident of Crimea arrested by the Russian Federal Security Service under suspicion of being a Ukrainian informant. The evidence against him was that he was an aviation and plane spotter hobbyist who used RTL-SDRs for listening in to aircraft communications - something of which many of us do in safety.
Back in June 2021 Stanislav was facing 25 years in prison. We still don't know what has happened to him. If anyone local has heard any updates please let us know. (UPDATE: US1GBF in the comments below knew Stanislav personally and has provided an update: Stanislav was reportedly transferred from Crimea to a Moscow prison. The Ukrainian authorities are working on the exchange of Stanislav. However, the exchange has already been postponed many times because of the refusal of the Russians to diplomacy. Work continues.)
From our website and sales statistics we know that there is a sizable RTL-SDR community in the Ukraine. We don't know what will happen if there is an invasion, but it's possible that, like in Crimea, Russian security forces will see SDR hobbyist activities as a threat, so we urge Ukrainian residents to have a plan to take down any web feeds and antennas should it come to the worst.
EDIT: This post has stirred up quite the discussion. As long as comments remain civil comments will remain open. This post is not intended to take sides. Whilst many Ukrainians in the amateur radio community already know to keep their activities safe during conflicts, we are aware of many young Ukrainian STEM students and hobbyists that may be somewhat insulated or not care about geopolitical events, who read our blog and copy activities that are safe to perform in most countries, but may not be safe in the Ukraine during times of conflict.
Over on Reddit u/onemindisbuddha has put together an interesting list highlighting the number of crowd sourced data aggregators that use RTL-SDRs or similar hardware.
A common example of a data aggregator that makes use of RTL-SDRs is most of the flight tracking websites, such as FlightAware and FlightRadar24. Contributors to the service will usually set up RTL-SDR + Raspberry Pi based receivers that feed ADS-B aircraft data received from the local area to these websites. Data from contributors from all over the world are then combined onto a single map, allowing for a global live picture of aircraft traffic.
Some other examples on the list that use RTL-SDRs include Amateur Radio APRS tracking, marine traffic, police/EMS audio feeds, train traffic, weather audio feeds, satellite ground station feeds and general web based remote SDR access. Added to the list are also aggregators based on other devices for applications like lightning detection and seismic activity reporting.
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.
