Tagged: airband

Listening to SELCAL and the HF Air Band with an RTL-SDR

Over on YouTube content creator Tech Minds continues to upload informative RTL-SDR based videos, this time discussing SELCAL and the HF Air Band. For international flights it is common for aircraft to communicate with ground controllers and the parent company via the HF bands.

As radio communications are sparse, and the pilots obviously don't want to monitor noisy HF static for the entirely journey a system is required for signalling pilots when a ground station wishes to communicate with them. The system in use today is SELCAL which simply consists of transmitting a set of tones unique to an aircraft. When a correct SELCAL tone is received the aircraft system alerts the pilots that a radio voice communication is about to come through, allowing them time to get the radio in operation. 

Tech Minds' video explains this in a bit more detail, and shows some examples of HF air comms with SELCAL tones played.

Using dump1090 in Windows

Dump1090 is a command line based ADS-B decoder for the RTL-SDR. It is considered by many to be the best ADS-B decoder for the RTL-SDR available at the moment. Dump1090 is most commonly used in Linux but over on his blog, SonicGoose has written a tutorial that shows how to use dump1090 on Windows with the popular PlanePlotter software. He also shows how to use ModeSMixer2, which is another command line utility that is used to combine data from multiple ADS-B decoders and then rebroadcast the combined feed.

SonicGoose writes that the reason that many PlanePlotter users are moving away from the simpler GUI based RTL1090 ADS-B decoder is because dump1090 provides better raw data to use for multilateration. Multilateration is a technique supported by PlanePlotter which used data shared from multiple receivers to determine the location of an aircraft, even if that aircraft is not transmitting location information.

Dump1090 Running on Windows
Dump1090 Running on Windows

New RTL-SDR ADS-B App for Android

Over on the Google Play store there is a new (released July 2014) RTL-SDR ADS-B Android app available for purchase called “ADS-B Receiver”. This app allows you to with the aid of an RTL-SDR and USB OTG cable, display live aircraft ADS-B data on your Android phone. This app can also be used to display the live ADS-B data in another app called “Avare”, which provides offline FAA aviation charts and other pilot tools on a Android phone.

The app can be downloaded as a trial version with a fixed limit on the number of packets allowed to be received, or the pro version for around $1.99 USD with no limits.

Previously on this blog we mentioned another similar RTL-SDR Android ADS-B app called “ADS-B on USB SDR RTL“.

ADS-B Receiver on Android
ADS-B Receiver on Android

Monitoring Multiple AM channels with RTL-SDR Airband

A new command line program for the RTL-SDR called RTL-SDR Airband has recently been released. The program can be used to simultaneously monitor multiple AM channels per dongle. It is intended to be used with online streaming services like liveatc.net which provide live audio streams of air traffic control communications around the world.

Its features include

  • Decode multiple AM channels per dongle (within bandwidth frequency range)
  • Auto squelch and Automatic Gain Control
  • MP3 encoding
  • Stream to Icecast or SHOUTcast server
  • Low CPU usage on Windows (<4% on i5-2430m) thanks to SSE and AVX instructions
  • FFT using GPU on Raspberry Pi (50-55% CPU with default clock)
Monitoring Multiple AM Channels with RTL-SDR Airband.
Monitoring Multiple AM Channels with RTL-SDR Airband.