In Testing: Customized Drivers for RTL-SDR Blog V3 SDRs

We've recently released a modified version of the Osmocom RTL-SDR drivers that has a few enhancements particularly for RTL-SDR Blog V3 units. The changes merge improvements to L-Band PLL locking performance which may be necessary for operating units in high ambient heat environments and the RTL_TCP performance enhancements by Stephen Blinick.

If you want to toggle the bias tee ON/OFF in SDR#, we've also made use of the "Offset Tuning" checkbox in the RTL-SDR settings. This checkbox is unused for R820T2 RTL-SDRs, so we've added code that will toggle the bias tee ON/OFF with this checkbox. 

In addition we've also made use of some unused EEPROM flags to create a method that allows you to force the bias tee to be always ON if a certain EEPROM flag is set. You can also force direct sampling mode with another EEPROM flag. Note that these force flags will only work if you are using these drivers.

A Windows release is available on the Github Releases. To use with SDR#, simply replace the rtlsdr.dll file in the SDR# folder with the one in the Release.zip file. To install on Linux, follow the instructions in the Readme, and remember to follow the instructions to remove librtlsdr-dev if you previously installed drivers via the package manager.

If there are any problems or feedback, please open an issue on GitHub. List of changes shown below.

1) VCO PLL current fix - Improves stability at frequencies above ~1.5 GHz https://www.rtl-sdr.com/beta-testing-a-modified-rtl-sdr-driver-for-l-band-heat-issues/

2) RTL_TCP ring buffer enhancement by Stephen Blinick https://www.rtl-sdr.com/significantly-improving-rtl_tcps-performance-with-ring-buffers/

3) Enabled direct sampling for rtl_tcp

4) rtl_biast program added, including the ability to turn on/off any GPIO

5) Hack to force the bias tee to always be on by setting the unused IR endpoint bit to 0 in the EEPROM. Example to force the BT to be always ON "rtl_eeprom -b y", to remove forced BT "rtl_eeprom -b n"

6) Hack to force direct sampling to be always on by setting the unused remote-enabled bit to 1 in the EEPROM. Example to force direct samping always "rtl_eeprom -q y". To remove forced direct sampling "rtl_eeprom -q n"

7) Repurposed "offset tuning" to toggle bias tee ON/OFF. We can now use the "offset tuning" button in SDR# and other programs to toggle the bias tee if there is no specific button in the GUI.
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GNU Radio Conference 2019 Videos now up on YouTube

GNU Radio Conference 2019 (GRCon19) was a conference about GNU Radio and projects based on GNU Radio that was held back in September 2019. GNU Radio is an open source digital signal processing (DSP) toolkit which is often used in cutting edge radio applications and research, and to implement decoders, demodulators and various other SDR algorithms. 

Yesterday videos from all the GRCon19 talks were uploaded to YouTube. The talks consists of many high level and cutting edge SDR topics. All talks can be found on their GRCon19 YouTube playlist, and matching slides on the GRCon19 website presentations page.

A list of the talk titles is pasted below.

  • Huntsville's Connection to Space
  • GNU Radio Project Update
  • Mega Hertz, Mega Samples, Mega bits, Mega Confusing
  • Man or Machine?: Developing a Turing Test for Radio Intelligence
  • UHD Four-O
  • Striving for SDR Performance Portability in the Era of Heterogeneous SoCs
  • Fixing the E310 Bottleneck: Implementing a High-Rate Heterogeneous FPGA DMA 
  • Determining Optimized Radio settings for specific waveforms
  • Software Defined Everything
  • GNU Radio Beyond 3.8 - A Technical Outlook
  • GNU Radio Enhancements for Space-Based Research
  • A decade of gr-specest -- Free Spectral Estimation!
  • Open Source Licensing
  • Spectrum Monitoring Network: Tradeoffs, Results, and Future Directions
  • The Future of Digital RFICs
  • Phase Synchronization Techniques
  • Synchronization: Core Concepts and Applications
  • AI and SDR: Software Meets Hardware Again...
  • Building a radio with M2K and spare parts
  • How we talked from the Moon: the Apollo communication system
  • gr-satellites: a collection of decoders for Amateur satellites
  • gr-iio: Nuances, Hidden Features, and New Stuff
  • Open Sourcing the Search for Extraterrestrial Intelligence
  • Multi-Vehicle Map Fusion Using GNU Radio
  • SigMF.
  • GPUDirect + SDR: How to Move One Billion Samples per Second over PCIe
  • Multichannel phase coherent transceiver system with GNU Radio interface
  • Exponent: Arbitrary Bandwidth Receiver Architecture
  • UHD Streaming with DPDK: Raising the Throughput Ceiling with Drivers in User Space
  • USRP based X-band Digital Beam Forming Synthetic Aperture Imaging Radar
  • The GNU Radio PDU Utilities
  • MetaSat: Metadata for Good
  • Enabling Precise Timing Control in SDRs
  • Managing Latency in Continuous GNU Radio Flowgraphs
  • VLBI with GNU Radio and White Rabbit
  • Performance Evaluation of MIMO Techniques With an SDR-Based Prototype
  • UAS Community Testbed Architecture for Advanced Wireless Research with Open-Source SDRs
  • Demonstration of GNU Radio Compatibility with a NASA Space Communications
  • Network Modem (GRCON2019)
  • Prototyping LTE-WiFi Interworking on a Single SDR Platform
GNU Radio Conference 2019
GNU Radio Conference 2019
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Mike Tests our RTL-SDR Blog L-Band Active Patch Antenna on an SDRplay RSP1a

Over on YouTube Mike Ladd (KD2KOG) from the SDRplay technical support team has uploaded a YouTube video showing him running our recently released RTL-SDR Blog L-Band Active Patch antenna on an SDRplay RSP1a. In the video he receives and decodes AERO signals from his car with his RSP1a powering the active patch antenna via the built in bias tee.

If you didn't already hear, we recently released an active (amplified + filtered) high performance patch antenna designed for receiving L-Band satellites such as Inmarsat, Iridium and GPS. The patch is designed to be easily mountable outside on a window, surface, stick, tree branch etc as it comes with easy to use mounting solutions and extension coax, and is enclosed in a fully weather proof plastic cover. If you're interested the product is available over on our store for US$39.95 with free shipping.

You also might want to keep an eye on Mike's YouTube channel, as he notes that in the yet to be released part 2 video he will be giving away the antenna in a competition.

RTL-SDR Blog L-band patch antenna part 1

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Tutorial on Performing a Replay Attack with a HackRF and Universal Radio Hacker

Over on YouTube channel Tech Minds has uploaded a short tutorial video that shows how to perform a replay attack with a HackRF and the Universal Radio Hacker software. A replay attack is when you record a control signal from a keyfob or other transmitter, and replay that signal using your recording and a TX capable radio. This allows you to take control of a wireless device without the original keyfob/transmitter. This is easy to do with simple wireless devices like doorbells, but not so easy with any system with rolling codes or more advanced security like most car key fobs.

In the video Tech Minds uses the Universal Radio Hacker software to record a signal from a wireless doorbell, save the recording, replay it with the HackRF, and also analyze it.

Universal Radio Hacker - Replay Attack With HackRF

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SignalsEverywhere: Testing Wideband PCB Antennas from Hex and Flex

In the past we've posted twice about Hex and Flex who has been designing and selling various types of wideband PCB antennas. Previously we saw his wide band vivaldi antenna, and his wideband 400/800 MHz+ spiral antennas.

Now on the latest episode of SignalsEverywhere host Corrosive gives us a brief review of the Hex and Flex antennas, and goes on to demonstrate the spiral antenna in action. In his tests he was able to receive Inmarsat AERO, 433 MHz tire pressure monitors (TPMS), 300 MHz APRS signals, 300 MHz SATCOM, 800 MHz P25 and 1090 MHz ADS-B aircraft tracking signals with the spiral antenna and our RTL-SDR Blog Wideband LNA.

The video also comes with a 20% off promotion code for the Hex and Flex Tindie store. Simply enter the code "signalseverywhere" at checkout.

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Dash Mounted ADS-B With an RTL-SDR Blog V3

Reddit user [Bobcalamarie] recently [posted] about how he uses his car dash mounted Android tablet along with an RTL-SDR Blog V3 and a magnetic mount antenna while sitting in traffic to track aircraft overhead.

We’ve seen something similar to this once before when [Signals Everywhere] uploaded a video showing off ADS-B reception (among other things) to a dash-mounted Windows tablet and an Android head unit.

The software used by Bobcalamarie is the Android [Avare ADS-B] software which can be found in the Google Play Store. However, other applications exist for Windows, Linux, and other operating systems as well. Some software such as [Virtual Radar Server] even allows you to set-up alerts for specific types of aircraft. Which while we wouldn’t condone it, it might come in handy for someone in traffic.

What would you do if you had an SDR installed in your vehicle? We would love to hear what you have to say in the comments below.

Dash Mounted ADS-B Reception
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ORBCOMM Receiver: New Open Source Software for Monitoring Orbcomm Satellites

Thank you to Frank for submitting his new RTL-SDR compatible Orbcomm Satellite monitor software called "Orbcomm Receiver". Orbcomm is a low earth orbit satellite communications system that operates in the 137 - 138 MHz frequency range. The satellites specialize in remote IoT and machine to machine (M2M) connectivity, an example use case being a GPS tracker on a shipping container regularly uploading GPS coordinates from anywhere in the world via the Orbcomm satellites. Orbcomm satellite signals are fairly strong and can easily be received with an RTL-SDR and V-Dipole antenna.

We haven't posted about Orbcomm on this blog since 2015 since there is not many interesting things to say about it. The data is all encrypted, and the only information you can really see is Orbcomm satellite ID, frequency and positioning data. Franks software doesn't change this fact, but his software is all open source, so it may be a useful tool for learning about satellite signal DSP processing. Frank writes:

There are a couple different projects out there to decode ORBCOMM signals (Orbcomm-Plotter and MultiPSK). What makes my project different from these is that I wrote it as a learning project. So all of the signal processing, written in Python, is available to the user and is decently documented. I hope this can be a good learning resource for people who want to see a practical example of satellite communications signal processing. Also, my software is open source and free to use.

Currently, the software can do offline or real-time decoding of a single ORBCOMM downlink channel. The transmitted bits of the ORBCOMM signal are demodulated and when the packet type is known, the packet information is decoded. There are a lot of ORBCOMM packets that can't be decoded and of course the message data is encrypted so that information is not available. But, there is still a ton of interesting information available.

The project is still in development so it has some limitations. For real-time recordings, I only support RTLSDRs currently. Also, I'm having trouble getting the real-time processing to work on mac OS, so currently that mode is only supported on linux. However, I have included a couple data files in the repo, so even without an SDR, users can experiment with the signal processing. I welcome any bug reports or suggestions.

Orbcomm Packet Decoding. Showing Realtime Satellite Position.
Orbcomm Packet Decoding. Showing Realtime Satellite Position.
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Creating a 21cm Galactic Sky Map with an Airspy and 1.8m Dish

Marcus Leech from ccera.ca is a pioneer in using low cost software defined radios for observing the sky with amateur radio telescopes.  In the past he's shown us how to receive things like the hydrogen line,  detect meteors and observe solar transits using an RTL-SDR. He's also given a good overview and introduction to amateur radio astronomy in this slide show.

His recent project has managed to create a full Hydrogen sky map of the northern Canadian sky. In his project memo PDF document Marcus explains what a sky map shows:

A [sky map] shows the brightness distribution over the sky for a given set of observing wavelengths. In the case of the 21cm hydrogen line wavelength, maps show the distribution of hydrogen over the sky. For amateur observers, such maps generally show the distribution within our own galaxy, since extra-galactic hydrogen is considerably more faint, and significantly red/blue shifted relative to the rest frequency of 1420.40575 MHz, due to relative motion between the observer and the target extra-galactic hydrogen.

He was able to make this observation using his radio telescope made from a 1.8m dish antenna, a NooElec 1420 MHz SAWBird LNA + Filter, a 15dB line amplifier, another filter and two Airspy R2 software defined radios locked to an external GPSDO. The system runs his custom odroid_ra software on an Odroid XU4 single board computer, which provides spectral data to an x86 host PC over an Ethernet connection. 

Over 5 months of observations have resulted in the Hydrogen sky map shown at the end of this post. Be sure to check out his project memo PDF file for more information on the project and how the image was produced. Marcus' blog post over on ccera.ca also notes that more data and different maps will be produced soon too.

Hydrogen Sky Map
Hydrogen Sky Map
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