Category: Airband

Showing what VOR and ILS Aviation Signals Look like in SDR#

Over on YouTube user RedWhiteandPew has uploaded two videos showing what VOR and ILS signals look like in SDR# with an RTL-SDR dongle. VOR and ILS are both radio signals used for navigation in aviation. 

VOR stands for VHF Omnidirectional Range and is a way to help aircraft navigate by using fixed ground based beacons. The beacons are specially designed in such a way that the aircraft can use the beacon to determine a bearing towards the VOR transmitter. VOR beacons are found between 108 MHz and 117.95 MHz.

RedWhiteandPew writes:

Here I am picking up the VOR beacon from KSJC. The coolest part is at the end of the video. I believe the signal moving back and forth is caused by the Doppler effect, because VORs transmit their signals in a circular pattern. The VOR wiki article has a GIF that shows how it works here https://en.wikipedia.org/wiki/VHF_omn…. If you play and pause the video at different points before I zoom in, you can see that the two signals on the side are the opposite phase.

ILS stands for Instrument Landing System and is a radio system that enables aircraft to land on a runway safely even without visual contact. It works by using highly directional antennas to create four directional lobes (two in the horizontal plane, two in the vertical) that are used to try and ensure the aircraft is centered and leveled on the approach correctly. The ILS frequencies are at 108.1 – 111.95 MHz for the horizontal ‘localizer’, and at 329.15-335.0 MHz for the vertical ‘glide slope’.

RedWhiteandPew writes:

Here I have tuned into one of KSJC’s ILS frequencies. You are able to hear the faint identifier beeping transmitting its ISL ID code which is ISJC. For comparison, I used to morse code translator website.

The reason I am hearing ISJC and not ISLV even though they are on the same frequency is because the localizers transmitting the signal are directional along the length of the runway. Since I am located to the south east of the airport, and I am within its transmitting beam, I am able to listen to it on a scanner.

If you’re interested in these signals then this previous post about actually decoding them might be of interest to you.

Visualizing the Traveled Path of a Weather Balloon, Tanker Boat and Gliders with an RTL-SDR and CesiumJS

Over on YouTube user pascal poulain has uploaded a short video that shows a timelapse of the flight path of a weather balloon in Cesiumjs as it rises and falls, as well as a time lapse of a marine tanker docking, with the signals received with an RTL-SDR. In a third video pascal also shows a visualization of glider flights tracked via FLARM and the Open Glider Network which also obtains most of it’s data through RTL-SDR contributors.

Cesiumjs is a tool similar to Google Earth. The main difference is that it works on a wider array of devices through a web browser without the need for any plugins. It is often used for visualizing data on the globe. An example of some of its many demos can be found here.

We’re not sure what tools pascal used, but over on GitHub there is a tool called airtrack which can be used together with dump1090 to display flights in real time on Cesiumjs.

Akos’ ADS-B Performance Comparison of 19 Different RTL-SDR Dongles

Over on his blog radioforeveryone.com author Akos has run a large comparative test of 19 different types and brands of RTL-SDR dongles on ADS-B reception. He takes multiple dongles from NooElecs Nano/Mini and SMArt range and our RTL-SDR Blog V3 unit and the FlightAware ADS-B optimized units. He also notes that E4000 based dongles such as the NooElec XTR are unable to receive ADS-B frequencies and excludes them from the test.

For his tests he used a Raspberry Pi 3 and compares two dongles at a time. The results are about as would be predicted. The tiny Nano dongles are usually the worst performers due to their trade off in size vs heat dissipation and internally generated noise. The standard sized dongles all perform about the same, but the dongles with heatsinking perform the best. Of course the FlightAware dongles still get the best ADS-B reception due to their significantly lower noise figure thanks to the built in ADS-B LNA.

One interesting finding is that Akos shows that heat does play a noticeable role in performance of these dongles at 1090 MHz. Akos noticed that the better heatsinking on the RTL-SDR Blog V3 or cooler days improved reception.

Some of the tested RTL-SDR dongles
Some of the tested RTL-SDR dongles

HamRadio360 Podcast: ADS-B Aircraft Tracking with an RTL-SDR

HamRadio360 is a bi-weekly podcast all about ham radio and related topics. On their June 13 podcast Nick, KK6LHR came on to discuss his experiences with decoding ADS-B with cheap SDR radio like the RTL-SDR. In the podcast they talk about the history of ADS-B, what it is, the difference between the 1090 MHz and 978 MHz frequencies, what all of the terms and acronyms mean, feeding sites like flightaware and flightradar24 and of course how to decode it with various forms of software packages.

Part of Nick's ADS-B Setup
Part of Nick’s ADS-B Setup

Creating an Encrypted ADS-B Plane Spotter with a Raspberry Pi, RTL-SDR and SSL

These days it’s quite easy to share your ADS-B reception on the internet with giant worldwide aggregation sites like flightaware.com and flightradar24.com. These sites aggregate received ADS-B plane location data received by RTL-SDR users from all around the world and display it all together on a web based map.

However, what if you don’t want to share your data on these sites but still want to share it over the internet with friends or others without directly revealing your IP address? Some of the team at beame.io have uploaded a post that shows how to use their beame.io service to securely share your ADS-B reception over the internet. Beame.io appears to be a service that can be used to expose local network applications to the internet via secure HTTPS tunneling. Essentially this can allow someone to connect to a service on your PC (e.g. ADS-B mapping), without you revealing your public IP address and therefore exposing your PC to hacking.

On their post they show how to set up the RTL-SDR compatible dump1090 ADS-B decoder on a Raspberry Pi, and then connect it to their beame-instal-ssl service.

Encrypted ADS-B Sharing with the beame.io service.
Encrypted ADS-B Sharing with the beame.io service.

Receiving ADS-B Jetliner Traffic with a Simple Paper Clip

Over on YouTube user icholakov has uploaded a new video showing how easy it can be to build a cheap ADS-B antenna out of a simple paper clip and coax connector. Modern aircraft carry an ADS-B transceiver and antenna which broadcasts the current GPS location of the aircraft. This is used for collision avoidance and air traffic control, but anyone with a receiver like an RTL-SDR can also receive and decode these signals, and plot locally received air traffic on Google maps. We have a tutorial for decoding ADS-B signals available here.

In the video Thomas Cholakov (N1SPY) explains the concept behind the antenna design, which is a standard 1/4 wave ground plane cut to the correct dimensions for ADS-B at 1090 MHz. He cuts 5 pieces of the same length, with one piece used as the active whip element, and four pieces used in the ground plane element. The paper clip pieces are then soldered onto a coaxial connector and then the antenna is ready to be used.

Asking an Amazon Echo to Spot Planes with help from an RTL-SDR and Raspberry Pi

Amazon Echo is a smart home device which is essentially a hands free speaker that responds to voice commands in a similar way to ‘Okay Google’ and Siri does on your phone. With voice commands you can ask it to do things like play music, make a call or send a message, answer any question, control smart home devices like fans and locks and order items from Amazon.

Over on his blog Nick Sypteras has written about teaching his Amazon Echo a new ‘skill’ which allows it to automatically detect and read out what aircraft is flying outside his window, and where it is going. A skill is basically a plugin that you can code up to give your Amazon Echo new voice command functions and behavior.

The Echo skill gathers the live local ADS-B plane data via dump1090’s json output which runs on a networked Raspberry Pi with RTL-SDR dongle attached. The data is loaded into a database, which is then queried for the closest plane to the Echo’s location. Finally the program scrapes the closest flights departure and arrival data from FlightRadar24 before speaking it through the Echo’s speaker. Nicks code is freely available over on his GitHub page.

This project reminds us of a previous post where we posted about Simon Aubury’s work in creating a Raspberry Pi and RTL-SDR based aircraft camera tracking system. Simon’s system used live ADS-B data to point a camera directly at aircraft as they passed over his house.

It also reminded us of this British Airways video billboard that was popular a few years ago. The ad featured a young boy who would point directly at passing aircraft with text displaying the flight information. They used a commercial networked ADS-B device to gather live ADS-B data (internet based ADS-B data from sites like flightradar24.com has a time lag, so it is not suitable for time sensitive applications like this), and whenever a passing British Airways aircraft was detected the ad would play.

Building a Ground Plane / Spider ADS-B Antenna for 2€

Thanks to Manuel aka Tysonpower for submitting to us his extremely cheap ADS-B antenna build. Manuels ADS-B antenna consists of a simple SMA connector with flange and some wires cut to the correct resonant length for 1090 MHz ADS-B. This ground plane design has been around for years on the internet with atouk’s guide being the most commonly used, although atouk’s design uses a larger SO-239 connector instead. Manuel takes the design one step cheaper by using cheap single core copper wire for the elements, and a low cost SMA connector. The wires are soldered onto the SMA connector flange so you will need to know how to solder to complete the antenna.

Manuel has uploaded a video which shows the build steps for his cheap antenna in a step by step guide. We note that the video is narrated in German, but there are English subtitles.