Back in 2015 we posted about the dsame software, which is a decoder for the American Emergency Alert System (EAS) which is encoded with the SAME (Specific Area Message Encoding) protocol. EAS transmits on the NOAA weather frequency.
The sirens appear to be activated wirelessly through the same frequencies that weather and EAS use, and so the signal can be monitored with an RTL-SDR or other SDR. When an active signal is present, the forked dsame software will decode the alert. The alert could then be used to activate a local siren or display.
How the SASMEX System Works (Credit: http://www.cires.org.mx/sasmex_n.php)
Recently we came across a new project called DeFli and DeSky, which appears to be plans for a decentralized network of RTL-SDRs. The goal of the project is to provide decentralized access to ADS-B and satellite data through the use of RTL-SDR ground stations. The RTL-SDR ground stations upload their data to the DeFli servers and in return ground station hosts receive compensation in DEFLI tokens via the DeFli blockchain.
From the website it appears they are focusing on selling the data to UAV and satellite operators, but there seems to be no reason why it couldn't be used for other purposes too.
The use of crowd sourced RTL-SDR data is nothing new, with successful ADS-B aggregators like FlightRadar24.com and adsbexchange.com already in operation. Projects like SatNOGs also exist which crowd source satellite data. Not to mention other RTL-SDR and radio data aggregators like marinetraffic.com for Marine AIS, amateur.sondehub.org for Amateur Radio Balloons, aprs.fi for APRS, and airframes.io for ACARS, VDL, HDFL and SATCOM data. However, this is probably the first radio data aggregator to incorporate blockchain concepts for host rewards.
In a Reddit Post (now removed but cached on Google), the creators wrote:
There is clearly an appetite from a large number of Helium Hotspot owners to utilize their hotspots for other projects with a view to getting a better ROI on their investment. That being said, I believe it is absolutely just and fair for Nova & the Foundation to take steps to prohibit the LoRa specific hardware from being used by competing projects both from a commercial perspective and also regulatory. Our personal belief is that Nova/Foundation should operate Helium Network as a NaaS and allow these newer "players" to piggyback on the equipment without compromising the regulatory side of things.
From an industry perspective there is of course a frustration at an awful lot of under-used/under-utilized hardware, specifically the CPU modules that remain in short supply, thus limiting the expansion capabilities of a hardware based network.
Likewise whilst Helium IoT paved the way for decentralized networks to become a "thing" there is also the counter-argument now that actually it is incredibly difficult to build a hardware based network because of the growing disdain. Now obviously part of that is linked to failed projects like MXC, Planetwatch and WeatherXM as well as dubious projects like RevoFi.
That brings me on to our project- DeFli (defli.org). I am not going to extol the virtues of the project, all I am going to give is a very brief "blurb". We are building a decentralized network of ground stations for unmanned aircraft to communicate with (to satisfy new legislation) and which will form the basis of an advanced traffic management system.
A "ground station" can be built from any Helium Hotspot without affecting the performance, nor do we utilize the LoRa Concentrator (ADS-B is broadcast over the 1090MHz frequency). To achieve dual "mining" it is simply a case of running DeFli in a Docker Container (can be viewed on our Github) and adding a USB RTL-SDR receiver.
WARNING: As with anything cryptocurrency related, do your own research first before putting any of your own money in. This project could very well be a scam, or it could just be a project in the early stages of getting started.
On his Medium.com blog, Mohsen Tahmasebi has posted an article about his journey into listening to satellites which started with his acquisition of an RTL-SDR Blog V3 dongle. The article begins by explaining his motivations for receiving satellites and how difficult hobbies like this are to get into in his home country of Iran. Despite the challenges he tasted success when he was able to receive NOAA APT signals on his second attempt using the included portable dipole antenna in a V-dipole configuration. Shortly after Mohsen was also able to receive Meteor-M2 LRPT.
Mohsen then built a more permanent V-dipole out of copper rods and optimized his antenna using NEC simulation software, finding that adding a reflector significantly improved reception. He then moved on to building a slightly more complex Turnstile antenna, which yielded even better results and allowed him to explore CubeSats at 435 MHz and contribute to SatNOGS. Finally, Mohsen ordered a Bullseye LNB and using a homemade bias tee, he received the QO-100 amateur radio transponder.
Overall, Mohsen's journey demonstrates that there is a lot of fun and learning available from internationally available satellites even in a country where equipment is hard to come by.
Mohsen's First Permanent V-Dipole for NOAA APT Reception
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.
He also added the "Flight controls on RTL 1090XHSI" software, which allows users to view a simulation of an aircraft cockpit, using real-time ADS-B data from the RTL-SDR.
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.
Guglielmo is a Linux, Windows (and in this recent update x86 MacOS) based RTL-SDR FM and DAB tuner software that supports SDRs including the RTL-SDR, Airspy, SDRplay, HackRF and LimeSDR. It is designed to be an easy to use program designed for media users, rather than hobbyist technical users.
Regarding the release of Version 0.5, Marco writes:
This release sports full mac (x86 only, sorry) and windows installers, DAB and FM scans and a preset editor.
Over on the Tech Minds YouTube channel Matt has recently showed us his build of DL5NEG's super simple diode based RF power sensor. The device is designed to detect and measure RF power, using a DC voltage meter and a calibration curve which converts the voltage detected by the diode into dBm. The simple diode based design is remarkably accurate, and could be a useful tool for testing or calibrating SDRs.
Matt's first build uses a simple copper PCB board, and although it is low precision the results he achieved match up pretty nicely with the calibration curves. In Matt's second implementation he created a proper PCB design using KiCad and PCBWay. After soldering the components with hot air, he found that the results were just as good when he tested the power output of his AntSDR E200.
Matt intends to use this sensor along with a simple ADC connected to a Raspberry Pi to measure the power going into his QO-100 setup via a -40 dBm coupler.
DCF77 is a long wave time keeping signal transmitting at 77.5 kHz from Frankfurt, Germany. It has been active since 1 January 1959. Using simple amplitude modulation, the signal encodes the current time and date, which is used by some devices like railway station clocks in Germany. Because it's a long wave signal transmitting at 50kW, it's possible to receive the signal across Europe, and sometimes even further away if propagation conditions are good.
Currently the decoder has been tested to work with an Airspy HF+ Discovery SDR, but it should work with any SDR capable of receiver 77.5 kHz if the GNU Radio source block is changed out.
