OneSDR New Posts: RF Filter Primer, Bias Tees, SDR Precautions

Over on a new SDR tutorial website, the authors have put up three new posts. The first post is part 2 of their "How Not to Break your Software-defined Radio (SDR) Hardware" series. This post covers mechanical strain considerations on connectors and reference clock input voltages. 

The second post titled "Software-defined Radios and Bias Tees" covers the use of bias tee's and the different voltage and current specs of bias tee's on different SDRs. They explain how these specs affect which LNA's you can use, and how some bias tee's are protected against over-current damage.

The third post is titled "A Primer on RF Filters for Software-defined Radio". In this post they cover topics like types of filters, insertion loss and preselectors on SDRs. 

OneSDR's Image used to explain Band Pass filters.
OneSDR's Image used to explain Band Pass filters.

GQRX Updates: GR3.8, New Color Maps, Bug and Performance Fixes

Since mid-January 2020 the popular Linux and Mac compatible SDR program GQRX has seen a number of new code commits over on it's git repository. Some of the updates include moving to GNU Radio 3.8, new color maps, as well as various bug and performance fixes.

At the moment these updates only appear to be available on the latest git code, so to get them you'll need to install GQRX from source via the instructions on the git readme.

Also thank you to @devnulling for providing us with the screenshot posted below which shows off the various new color maps available for the FFT waterfall.

GQRX Updated Color Schemes
GQRX Updated Color Maps

ADSBExchange now using tar1090: Historical Flight Tracks, Military Aircraft Filters and more

ADSBExchange is an aircraft tracking website service which aggregates ADS-B data from contributors running RTL-SDR's or similar receivers worldwide.

However, unlike other flight tracking sites such as flightaware and flightradar24, ADSBExchange sets themselves apart by proudly refusing to censor the tracking of military and private jets that have requested privacy. One area where this refusal to self-censor helps is with the "Dictator Alert" service. This is a service that automatically tracks the movements of private aircraft owned by authoritarian regimes via the ADS-B data collected and shared by ADSBExchange. 

Recently ADSBExchange upgraded their web interface moving from the old Virtual Radar Server system to tar1090 which is a more fully featured open source display for dump1090. This new interface has some great features, like the ability to view the complete flight track history of any aircraft on a particular day, the ability to display only military aircraft and the ability to filter by altitude and aircraft type. new tar1090 interface new tar1090 interface
Viewing the tracks of 1-day of police helicopter activity in the new ADSBExchange tar1090 interface.
Viewing the historic tracks of 1-day of police helicopter activity in the new ADSBExchange tar1090 interface.

New 978 MHz UAT Specialty RTL-SDR and Antenna and Dual 1090 & VHF Antenna from RadarBox

Over on Amazon we've recently seen the release of a 978 MHz UAT specialty RTL-SDR and 978 MHz tuned antenna by the flight tracking service known as AirNav RadarBox. The RTL-SDR appears to be similar to their 1090 MHz RTL-SDR version, which contains a SAW filter and LNA onboard the RTL-SDR. Due to the built in filter, this dongle will only work at the 978 MHz frequency. Like the 1090 MHz version, the dongle itself is priced at only US$14.95, and the antenna at US$49.95.

Universal Access Transceiver (UAT) is an alternative to ADS-B that is available only in the USA. It is typically used by smaller aircraft, transmits at 978 MHz, and apart from it's tracking system it has some additional advantages for pilots over 1090 MHz ADS-B, like the ability to receive alerts, weather data and radar plots. With an RTL-SDR and appropriate software these data services can also be received.

In addition they have also released some other interesting products including a 1090 MHz ADS-B with 118-136 MHz VHF airband antenna stacked on top of the ADS-B element for US$49.95, and an external ADS-B 1090 MHz filter for only US$14.95.

As an alternative to an RTL-SDR UAT receiver, we note that the Stratux has a hardware radio based UAT receiver available which has significantly lower power consumption. Although the receiver itself appears to be currently out of stock.

We note that we also currently have our 1090 MHz AirNav Radarbox Antenna + ADS-B optimized RTL-SDR set on sale for only US$39.95 + shipping, which is cheaper than you can find it elsewhere. Visit our store for ordering information.

The AirNav RadarBox 978 MHz UAT Optimized RTL-SDR and Antenna.
The AirNav RadarBox 978 MHz UAT Optimized RTL-SDR and Antenna.
New RadarBox 1090 MHz Filter and 1090 MHz & VHF Antenna single antenna.
New RadarBox 1090 MHz Filter and 1090 MHz & VHF Antenna single antenna.

OpenAstroTracker: 3D Printed DSLR Tracking Mount may be useful for Antennas Too

OpenAstroTracker is a recently published open hardware 3D printed tracking mount designed to move DSLR cameras for astrophotography. The mount supports heavy long lenses, so we think that this mount could also have the ability to move long directional antennas for satellite tracking. It could also be interesting to modify it for automatic aircraft photography, similar to what we've seen in this previous post where a Raspberry Pi camera on a pan-tilt mount was used with ADS-B data from an RTL-SDR to track aircraft in the sky with the camera.

The 3D printer files are available on Thingiverse, and the mechanical and electronics build guide, and Arduino code is available on GitHub. The build seems to be quite a bit easier compared to a SatNOGS rotator which is another 3D printed open hardware rotator, but it is yet to be seen what sort of antenna sizes it could rotate.

OpenAstroTracker: Could be modified for satellite tracking.
OpenAstroTracker: Could be modified for satellite tracking.

Opening a Parking Barrier with a HackRF Portapack and a Replay Attack

Over on YouTube user kwon lee has uploaded a video demonstrating a replay attack against a parking barrier arm. The tools he uses are a HackRF and Portapack running the Havok firmware. A replay attack involves recording a control signal with the HackRF+Portapack, and then replaying it later with the transmit function of the HackRF. If no wireless security mechanism like rolling-codes are used, simply replaying the signal will result in the transmission being accepted by the controller receiver.

As he has access to the remote control he records the transmission that is sent when the open button is pressed on the remote. Later once outside he shows how transmitting with the HackRF+Portapack results in the barrier arm opening.

This reminds us of a previous post where we noted how a HackRF was used to jam a garage door keyfob to prevent people from leaving in the TV show "Mr. Robot".

RF Replay Attack _ Parking-Breaker with HackRFone+Portapack+havoc

Michael Ossmann & Kate Temkin Present Software Defined Everything with GreatFET One

At the Hackaday Supercon Michael Ossmann & Kate Temkin presented a talk called "Software-Defined Everything" where they demonstrated some applications of the "GreatFET One" interface board. Michael Ossmann is best known for creating the HackRF software defined radio which is a highly versatile and low cost open hardware/software SDR transceiver. His company Great Scott Gadgets also employs Kate Temkin who is the lead software developer who worked on their latest product called the GreatFET One.

The GreatFET One is a multi-purpose digital interface board that plugs into a PC via USB. It contains multiple digital IO pins, supports SPI, I2C, UART and JTAG serial protocols, can do logic analysis, and also has a built in ADC and DAC.

In the talk Michael and Kate show how a simple light sensor can be plugged into the GreatFET's ADC, allowing the sensor's data to be digitized and processed in GNU Radio. This results in a software defined light sensor. By analyzing the light data in the frequency domain via an FFT graph they're able to determine the refresh rate of the ceiling lights.

Later they also show how GreatFET can be combined with i2C sensors and GNU Radio to do creative things like use an accelerometer as a microphone for a guitar pickup, with audio effects like guitar clipping controlled by GNU Radio blocks.

Michael Ossmann & Kate Temkin - Software-Defined Everything

OpenWebRX Version 0.18.0 Released: New Decoders for Digital Voice, Digital Ham Modes and More

Back in early January we posted about how the popular web based SDR and RTL-SDR compatible receiver software known as OpenWebRX was officially discontinued by the original author. However, thanks to it's open source licence, code contributor Jakob Ketterl (DD5JFK) has been able to continue developing the code and is taking over as the lead developer on his own fork of the code.

Recently he released version 0.18.0 of OpenWebRX which includes a few major upgrades including the much needed shift to Python 3, and the inclusion of multiple new decoders for DMR, D-Star, YSF, NXDN, FT8, FT4, WSPR, JT65, JT9, APRS and Pocsag.

Hello fellow radio enthusiasts,

with great excitement I would like to announce the availability of OpenWebRX Version 0.18.0 as public release. This is the first release of the project in some time, and the first release since I started working on it, so I’m more than happy to bring this to you.

What’s new? Quite a lot, actually. For those that haven’t had the chance to follow the progress of the project in the past months, here’s a quick overview:

    • Most of the server code has been rewritten for better flexibility, stability and performance. The project is now fully based on Python 3.
    • Large parts of the frontend code have been updated or polished.
    • The new core now supports multiple SDR devices simultaneously, as well as switching between multiple profiles per SDR, allowing users to navigate between multiple bands or frequencies.
    • Added support for demodulation of digital voice modes (DMR, D-Star, YSF, NXDN).
Added support for digital modes of the WSJT-X suite (FT8, FT4, WSPR, JT65, JT9).
  • Added support for APRS.
  • Added support for Pocsag.
  • Bookmarks allow easy navigation between known stations.
  • Background decoding can transform your receiver into an automatic reporting station, including automatic band scheduling.
  • The integrated map shows digimode spots as well as APRS and YSF positions.
OpenWebRX 0.18.0 is available via the following channels: Please check out our updated Setup Guide along with the rest of the documentation on the Wiki!

Questions, ideas, problems? Get in touch with the community at [email protected]!

Best regards and vy 73s

Jakob DD5JFK

We're so glad to see that this excellent software isn't dead in the water and is in fact thriving. We will continue to follow the Jakob's and the OpenWebRX communities' future developments. If you are interested, you can follow OpenWebRX development on the OpenWebRX forum.

OpenWebRX Screenshot
OpenWebRX Screenshot