Jack notes that he makes use of legal live ADS-B flight data from public data aggregators like Airplanes.live and AirFramesIO. ADS-B data is most commonly provided from contributors with RTL-SDR dongles running on Raspberry Pi single board computers.
The FCC does not prohibit the collection of unencrypted radio signals such as ADS-B and ACARS. This is done by thousands of feeders who give data to websites like @live_airplanes, TheAirTraffic, @AirframesIO, and ADSBexchange.
Even without Sweeney's social media accounts anyone can legally look up this live public flight data data, or even receive it themselves directly from the aircraft if they are close enough. Although a point can be argued that the social media accounts run by Sweeney make it significantly easier for this information to be obtained and shared by anyone.
Over on the Tech Minds YouTube channel Matt has posted a video tutorial that shows how to build a cheap quarter wave ground plane antenna tuned for 1090 MHz. This is the frequency of ADS-B (Automatic Dependent Surveillance–Broadcast), which is a signal broadcast by aircraft that can be used to track their GPS location.
The antenna is created from an SMA chassis mount socket, one copper wire for the receiving element, and four copper wires for the ground plane. They are soldered directly onto the socket. An LNA is added to improve reception.
Make Your Own Aircraft Tracking Antenna With RTL SDR
Over on his YouTube channel Tall Paul Tech has uploaded a video that demonstrates the FM (frequency modulation) capture effect. Apart from the costs and difficult logistics to change from AM to FM worldwide, the FM capture effect may be one additional reason as to why aircraft still choose to use AM modulation for communications instead of FM.
The FM capture effect is a phenomenon that occurs when two FM transmitters transmit on the same frequency at the same time. What will happen with FM is that the stronger of the two transmissions will be the only one heard, with the weaker one totally muted. This is in contrast to AM where both signals can be heard, albeit garbled like two people talking at the same time.
With aircraft this is important as for example if some aircraft accidentally leaves a blank transmission open, another aircraft can still transmit on top of the blank transmission and still be heard. Or allowing air traffic control to hear if multiple aircraft are trying to transmit at once, and handle communications appropriately based on urgency. The disadvantage is that without the capture effect, AM is more prone to interference from interference and atmospheric noise like lightning.
In his demonstration Paul uses two HackRF's with their clocks linked and an RTL-SDR to simulate two transmitters and a receiver.
Aircraft transmit multiple types of radio signals, including ADS-B and VDL2. ADS-B (Automatic Dependent Surveillance-Broadcast) is an air traffic surveillance technology that enables aircraft to broadcast their GPS position and other data. VDL2 (VHF Data Link Mode 2) is a digital VHF signal, allowing pilots to exchange text information with ground controllers and/or airline ground support. VDL2 is not designed to provide real-time positional data like ADS-B; however, positional information is often broadcast, and the VHF signals can propagate over longer distances.
Pilots of RC planes and drones need to be aware of the area they are flying in, to make sure that they stay well out of the path of manned aircraft. However, this can sometimes be difficult with aircraft like police helicopters that could rapidly show up anywhere. Drones typically do not have ADS-B transmitters due to size/weight and price, but it is still possible for drone pilots to use ADS-B receivers to make their flying safer.
Over on YouTube user xjet has come up with a solution involving the use of a portable ADS-B alarm for drone pilots. The ADS-B receiver consists of a 3D printed enclosure containing a Raspberry Pi Zero 2W, LCD screen and an RTL-SDR dongle connected to an ADS-B whip antenna. xjet notes that when his code and 3D enclosure are finalized, he will release the design for free as open source over on http://www.rcmodelreviews.com.
The idea behind the ADS-B alarm appears to be that drone pilots will receive an alarm when they are within the vicinity of an aircraft. Assuming the drone is not too far away from the pilot (as rules specify drones must be flown within visible distance) the alarm being next to the drone pilot should be sufficient. xjet notes that we cannot rely on live ADS-B aggregation websites like FlightRadar24 due to their censorship of certain aircraft like police, military and some private jets, or due to possible lack of coverage, so a local receiver will be a better solution.
After more than two years of development and testing the ADSB alarm for RC plane and drone flyers is almost ready to go. I will be posting the full build details including an SD-Card image, source code, wiring diagrams and STL/DWG files for the case to the RCModelReviews website in the next week or so. This is a totally open-source project which I give freely to the hobby community so as to increase the levels of safety associated with our activities.
It is through the use of this technology that we can show how taking practical steps towards ensuring safety is every bit as important (if not more so) than blindly following regulations written by those who have probably never even flown an RC plane or drone themselves.
Over on YouTube we've found an interesting project by RingingResonance where he's created a simulated traditional radar scope using a real analog radar scope tube, and ADS-B data gathered from an RTL-SDR running dump1090 on a Raspberry Pi 3B.
The project uses a real radar scope tube which is controlled by SPI signals sent from the Raspberry Pi into a DAC, which is in turn connected to the analog radar scope. RingingResonance has uploaded the open source code to GitHub. He notes that the code currently pushes the Raspberry Pi 3 to it's limits, so the sweep speed is limited.
Today news has come out that ADS-B Exchange (ADSBx) founder Dan Streufert has sold ADSBx to a private firm called JETNET for (an estimated) $20 million. Dan was the sole owner of ADSBx, and after the sale he remains employed by JETNET. JETNET is a firm that provides aviation market intelligence to business customers.
UTICA, NY - JETNET, a leading provider of aviation data and market intelligence, announced today that it acquired ADS-B Exchange, one of the world’s largest networks of ADS-B/Mode S/MLAT feeders and providers of real-time and historical flight data. The acquisition is the second of what the company anticipates will be several future acquisitions as JETNET expands its data-driven product offerings for the aviation industry.
Founded in 2016 by Dan Streufert, ADS-B Exchange aggregates approximately 750,000 messages per second worldwide via receivers hosted by aviation enthusiasts around the world. The acquisition of ADS-B Exchange will enable JETNET to expand its flight data solutions with real-time information.
“ADS-B Exchange was founded as the go-to resource for aviation and flight-data enthusiasts,” said Dan Streufert, President and Founder of ADS-B Exchange. “Joining forces with JETNET is the perfect match as we look to meet the business needs of our users while maintaining our enthusiast roots and unfiltered data. With a long history of providing highly valuable data to the aviation industry, JETNET offers the resources we need to accelerate our growth.”
Like JETNET, ADS-B Exchange serves numerous constituents across the aviation industry, including Maintenance, Repair, Overhaul (MRO), airport operations, and aircraft leasing. In addition, its real-time data is used by dozens of commercial customers across numerous end markets, including aerospace & defense, government, research/academic, and financial services.
“We are committed to providing our customers with innovative product offerings which provide the information and intelligence they rely on to make critical business decisions,” said JETNET CEO Derek Swaim. “We’ve long admired ADS-B Exchange and know how strategic the company’s real-time data offerings are to the aviation industry. Dan has done an incredible job building a fast-growing business that customers love. We believe he, and the ADS-B Exchange platform, will bring significant value to our customers.”
As a leading provider of aviation market information, JETNET delivers comprehensive and reliable business aircraft research to its exclusive clientele of aviation professionals worldwide. JETNET is the ultimate source of information and intelligence on the worldwide business, commercial, and helicopter aircraft fleet and marketplace, comprising more than 110,000 airframes. Headquartered in its state-of-the-art facility in Utica, NY, JETNET offers comprehensive, user-friendly aircraft data via real-time internet access or regular updates. JETNET is a portfolio company of Silversmith Capital Partners.
ADSBExchange.com is an open source aggregator of ADS-B aircraft tracking data, contributed by volunteers who are all mostly running RTL-SDR radio dongles and Raspberry Pi based feeders. ADS-B data is transmitted at 1090 MHz and can be used to track aircraft movements.
Outrage over the sale has been expressed on Discord by various ADSBx open source co-developers who objected to the sale and appear to have received no compensation from the deal. The outrage has resulted in some co-developers actively encouraging that volunteer feeders remove their station from the ADSBx network. Several hundred of the over 9000 feeders have already disconnected their feeding stations, and the count is dropping (at the time of this post there were 9234 feeders).
Unlike similar ADS-B aggregators like FlightAware, FlightRadar24 and RadarBox, ADSBx is open source and promises to never censor the ADS-B data of billionaires, political leaders, military, police or other sensitive private aircraft. This has caused discussion over whether this free speech absolutist stance is either less or more moral. At the moment it is unclear if the acquisition will result in any ADSBx censorship policies changing.
Famously the @elonjet account (now @ElonJetNextDay) on Twitter used data from ADSBx. This account was used to automatically tweet out the location of Twitter owner Elon Musk's private jet in real time. The @elonjet account along with the @adsbexchange account was banned from Twitter shortly after Elon Musk's child had an altercation with a stalker. Legal action was threatened against @elonjet and "organizations who supported harm to [Elon Musk's] family" which could imply that ADSBx is in the legal action firing line.
While the sale may be discouraging to some, the project is still entirely open source, so it seems that only the branding and rights to the data collected have been sold. The following is entirely speculation on our behalf, but given that ADSBx was likely not very profitable and struggling to cover operating costs from donations only, and the threat of substantial legal action being taken against it's sole owner, the sale seems like the smart decision for the founder. We hope that the co-developers will receive some fair compensation as well.
ADS-B Exchange has been key to projects like "Dictator Alert" which tracks the real time location of the private jets of known dictators.
The Organized Crime and Corruption Reporting Project (OCCRP) has also made use of ADS-B Exchange data in the past to uncover the role that US civilian aircraft contractors are playing in the East African "kill chain".
Media have also used ADS-B Exchange to track the movements of the military aircraft like Black Hawk Helicopters and CBP Predator drones that were used to monitor crowds during the George Floyd protests.
SDRangel is a free open source software defined radio program that is compatible with many SDRs, including RTL-SDRs. SDRAngel is set apart from other programs because of it's huge swath of built in demodulators and decoders.