At the beginning of 2020 Annunaki (@StupotSinders) released his third party user interface for DSDPlus. DSDPlus is a digital speech decoder capable of decoding protocols such as P25 P1, DMR, NXDN and more with an SDR such as the RTL-SDR. As it is a command line tool, it can be a little daunting for some users, which is where the GUI comes in handy.
Recently Annunaki has released an SDR# plugin version of DSDPlusUI. This makes it so you can visualize the digital voice signals at the same time as controlling and decoding with DSDPlus. The plugin is available on the DSDPlusUI website at dsdplusui.com. To use it you will need to be using SDR# 1777 or later.
Over on YouTube popular science content creator Steve Mould has uploaded a video showing how he was able to open his own car using a HackRF software defined radio. In the video Steve first uses the Universal Radio Hacker software to perform a simple replay attack by using his HackRF (and also an RTL-SDR V3) to record the car's keyfob signal away from the car and replay it near the car.
Steve goes on to note that most cars use rolling code security, so a simple replay attack like the above is impractical in most situations. Instead he notes how a more advanced technique called "rolljam" can be used, which we have posted about a few times in the past. Later in the video Steve interviews Samy Kamkar who was the security researcher who first popularized the rolljam technique at Defcon 2015.
In this episode of Frugal Radio's ongoing SDR guide videos Rob demonstrates how you can use an RTL-SDR with DSDPlus to monitor DMR and NXDN digital voice radio communications. Rob writes:
With a simple Software Defined Radio (SDR) and some free or frugal software, you can monitor digital radio systems like DMR and NXDN in your area.
his video is a demonstration of how I set up DSDPlus to monitor DMR and NXDN networks, and shows how to modify the various files that help the software trunk track the system with your SDR.
More details with links to the software (DSDPlus) and hardware (1 x RTL-SDR v3) I used in this video can be found at https://frugalradio.com/monitor-dmr
f you are unsure about how trunking systems work, I suggest watching the overview at the beginning of Episode 6 - https://youtu.be/zuUTXHbUvpw
2020 SDR Guide Ep 7 : Trunk DMR & NXDN digital with DSDPlus and 1 RTL-SDR
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
Simple DMR decoder. No external dependencies, no settings, uses SDR # audio path. Designed for listening to unencrypted DMR channels. The voice from both slots is mixed into one channel.
To install the plugin simply copy the dll's from the zip file into the SDR# folder, then copy the line from the magline.txt text file into the plugins.xml file which can be opened with any text editor.
We've posted about Job Geheniau's RTL-SDR radio telescope a few times in the past [1] [2] [3], and every time his results improve. This time is no exception as he's created his highest resolution radio image of the Milky Way to date. We have uploaded his PDF file explaining the project here.
Job used the same hardware as his previous measurements, a 1.5 meter dish, with 2x LNA's, a band pass filter and an RTL-SDR. Over 72 days he used the drift scan technique to collect data in 5 degree increments. The result is a map of our Milky Way galaxy at the neutral Hydrogen frequency of 1420.405 MHz.
JRT - Northern sky Hydrogen Line Survey with RTL-SDR
This image is quite comparable to an image shown in a previous post which was created by Marcus Leech from CCERA who used a 1.8m dish and Airspy.
If you're interested in exploring our Galaxy with an RTL-SDR via Hydrogen Line reception, we have a simple tutorial available here. The ideas presented in the tutorial could be adapted to create an image similar to the above, although with lower resolution.
John from JR Magnetics has written in and wanted to share his Kickstarter for a US$50 ultra wide band antenna that he has designed. The size is a just little bit bigger than two credit cards and the advertised coverage is from 750 MHz up to 6 GHz with a VSWR of less than 2.0.
John's Kickstarter text reads below:
Flat Ultra Wide Band Antenna Suitable for SDR
About
I was never satisfied with the commercially available wide band antennas. They were all too large or did not have suitable VSWR over the frequency range generally required by SDRs. I read many research papers and ultimately made a omni-directional ultra wide band antenna, but it was too expensive for most people. Details regarding that antenna can be found at https://www.rtl-sdr.com/constructing-a-3d-printed-wideband-900-mhz-to-11-ghz-antenna/
However, a bi-directional antenna was good enough for most people, so I have made a flat one. The antenna I ended up with is 5 inches by 4 inches and about 3 mm thick with an SMA connector. It is quite definitely not a square patch antenna, which usually has a narrow bandwidth.
This antenna has a VSWR measured to be under 2.00 from around 750 MHz to over 3 GHz. It simulates to have a VSWR under 2.00 out to over 6 Ghz. This is enough for most of the available SDRs. It works very well with WiFi, Bluetooth, Zigbee and other systems within the bandwidth.
Typical Directional Log Antenna
Existing Antennas
The log antenna, Figure 2, has a wide bandwidth, but it is specified as having ranges, because the VSWR rises over 2.00 several times over that range. The antenna measure sover 40 centimeters long, which is problem for me in a laboratory setting. It is too large to fit anywhere and wants to be permanently fixed to a pole or something like that.
The other antenna I have is a discone type device, Figure 3. It is huge. There is not practical for it to fit on a lab bench around various RF devices. It is measures around 28 centimeters at its base. It needs to be elevated above any ground planes, which complicates a laboratory environment with metal bench tops. I have it sitting on a shelf above the computer monitors on the opposite side of the room away from the lab bench. This does not work well when I am trying to deal with wireless devices connected to USB hubs on the bench with short range features.
Discone Type Wide Band Antenna
Figure 4 shows the Flat Antenna next to the Log Antenna for a size comparison that illustrates just how much space saving there is with this new device. This is no small feat. This Flat Antenna is useful around all manner of RF devices on the bench without causing space issues, getting in the way of instruments and couples well with all of the wireless devices I am using. It is small enough with a convenient shape for moving it around and keeping it above a metal bench top. It only needs to be a few centimeters above any ground planes when perpendicular, not horizonal.
Due to its size and shape, near field problems have not been a problem, as with the other antennas. The antenna is quite directional, which is not much of a problem, since the RF bounces around all over the place. A Faraday shield is the only way to keep this device from picking out everything in the vicinity. The neighbors IoT devices create mountains of RF clutter. This antenna picks up all of it. If you only want restricted bandwidths, band pass and reject filters can be used. The load impedance is 50 Ohms across the band making an excellent match for all of the filters I have here.
Our Flat Antenna Size Comparison with the Log Antenna
Specifications
Figure 5 shows the VSWR as measured by the NanoVNA Version 2. It only goes out to 3 Ghz. The device must be calibrated before use, or you will get extraneous results. I am told the VSWR never goes above 2.00 until after 6 GHz. This is a remarkable antenna. I never found anything comparable to it on the Internet.
It can be used for all wireless and SDR applications normally within the 750 MHz to 6 GHz bandwidth. This is not guess work or speculation. The network analyzer shows the response clearly.
The antenna is 5 inches long by 4 inches wide by roughly 3 mm thick, not counting the SMA connector.
VSWR of Our Flat Antenna
What You Get
You get one (1) antenna, as shown in Figure 1, for each US$50. You cannot do this yourself for that price. Your time alone is worth more than that after you do the calculations, simulations and prototyping. You also would have to deal with fab shops to get this done correctly, which is not always convenient for many people.
In other words, this is a remarkable Ultra Wide Band Antenna at a remarkable price.
Engineering
This has already been done. I have a Masters Degree in RF Engineering. I also have all of the simulation tools that are not available to most people, with the exception of some university students.
Manufacturing
I have sources that I use all the time. I just put this one into the queue. We also have a minimum order, which is why we Crowd Fund this operation.
Timeline
Once in the queue, it takes about two (2) weeks. After that, we are only concerned with delivery time. We intend to use ordinaty Postal Service mail, to keep the cost down, so time of delivery may vary depending upon the destination.
Risks and challenges
We already have laboratory results, so there is nothing to risk in performance. The only other thing that could be troublesome is the lead time by the vendor that manufactures the main component or any delays caused by the Postal Service.
UPDATE 16 Dec 2020:John has provided us with this document that addresses a few questions people had about the antenna.
AirNav is the company behind RadarBox24.com, a flight data aggregation service similar to sites like FlightAware.com and FlightRadar24.com. RTL-SDR hardware is typically used to receive ADS-B, and like other providers AirNav have their own custom ADS-B optimized RTL-SDR unit. In addition they sell RTL-SDR's optimized for UAT 978 MHz and the VHF Airband. They also have a range of ADS-B/UAT/VHF airband outdoor antennas as well as filters.
Currently their products are discounted by 20% for Black Friday/Cyber Monday sales. The discount is available on Amazon, as well as directly from their store with coupon GET20.
