Over on YouTube icholakov has uploaded an informative video that gives an overview of the main communication modes that aircraft use from HF to UHF. In the video he also gives examples of those modes being received and decoded with an SDR.
The modes that he explains and demonstrates are VHF voice, VHF ATIS automated weather, ACARS short data messages, HF voice, HF automatic weather, HF data selective calling (SELCAL), HF data link (HFDL) and UHF ADS-B aircraft positioning.
2018: Monitoring airplane communications (aviation radio signal monitoring via sdr)
Over on YouTube Fuzz The Pi Guy has uploaded a video tutorial showing how to set up a Broadcastify air traffic control audio feed with RTL-Airband and an RTL-SDR running on a Raspberry Pi. This allows you to publicly share your received air traffic control audio online via sites like Broadcastify.
The video is based on a comprehensive Radioreference text tutorial which takes you through the process from scratch. Setting it up involves installing the Raspbian OS, installing RTL-SDR, installing and setting up RTL-Airband, configuring ezstream and then ensuring that everything runs automatically on boot. It's a fairly involved setup process, but the video helps make things easier.
How To Setup Broadcastify On A Raspberry Pi Using RTL_AM For Aviation
RPiTX is software for the Raspberry Pi which can turn it into a 5 kHz to 1500 MHz transmitter which can transmit any arbitrary signal. In order to transmit the software does not require any additional hardware apart from a wire plugged into a GPIO pin on the expansion header. It works by modulating the GPIO pin with square waves in such a way that the desired signal is generated. However, although additional hardware isn't required, if RPiTX is to be used in any actual application a band-pass filter is highly recommended in order to remove any harmonics which could interfere and jam other radio systems.
Earlier this month RPiTX was upgraded to version 2. One of the changes is a new GUI for testing the various transmission modes. Currently it is possible to transmit a chirp, FM with RDS, USB, SSTV, Opera, Pocsag, SSTV, Freedv. There is also a spectrum painter which allows you to display an image on a SDR's waterfall.
The RPiTX V2 GUIPainting an Image on a SDR Waterfall Display with RPiTX v2
The RPiTX v2 update also makes recording a signal with an RTL-SDR, and replaying that signal with RPiTX significantly easier. Previously it was necessary to go through a bunch of preprocessing steps (as described in our previous tutorial) in order to get a transmittable file, but now RPiTX is capable of transmitting a recorded IQ file directly. This makes copying things like 433 MHz ISM band remotes significantly easier. One application might be to use RPiTX as an internet connected home automation tool which could control all your wireless devices.
Finally, another application of the RPiTX and RTL-SDR combination is a live RF relay. The software is able to receive a signal at one frequency from the RTL-SDR, and then re-transmit it at another frequency in real time. Additionally, it is also capable of live transmodulation, where it receives an FM radio station, demodulates and then remodulates it as SSB to transmit on another frequency.
The RPiTX V2 RTL-SDR MenuRPiTX v2 re-transmitting a broadcast FM signal live at 434 MHz.
Over on YouTube user Petr Horký has uploaded a helpful tutorial video showing how to install GNU Radio on Windows 10. Petr goes through the steps from installing Python, pip and other dependencies like numpy and pyqt, to installing GNU Radio itself and then ensuring that the system PATH is set correctly.
GNU Radio is a block based programming language for building digital signal processing applications (e.g. demodulators/decoders). It is very useful for experimenting with more advanced SDR concepts, and there are also many RTL-SDR compatible applications built with GNU Radio as well. GNU Radio is typically run on Linux, but can also run on Windows now too, although perhaps not every program will be compatible.
How to install GNU Radio Companion on Windows 10 (pip, environment variables)
First, we'd like to thank all those who've pre-ordered a KerberosSDR unit already. The response has been overwhelming, and we've raised so much more than we originally thought. Thanks to your support, we've been able to immediately fund continued development on the open source demo software. We aim to release the software when we ship, and we'll have another update then. On the Hardware side, we've already begun ordering some components, and have started prototyping the metal enclosure that will come stock on all KerberosSDR units. We are still on track for a late December/early January shipping date.
If you haven't pre-ordered yet, get in quick as the campaign and pre-order discount ends today! Although all 600 early bird discounts have been taken, it is still possible to pre-order KerberosSDR for $125. Afterwards, the price will rise to a maximum of $150.
Over the next month of manufacturing we intend to begin releasing tutorials that show how to use the board and demo software for passive radar and direction finding experiments. We'll also show some other use cases, like how KerberosSDR could be used as four separate RTL-SDRs for monitoring multiple frequencies simultaneously.
KerberosSDR with Calibration Board Attached (Metal Enclosure with SMA connectors Not Shown)
If you weren't already aware, over the past few months we've been working with the engineering team at Othernet.is to create a 4x Coherent RTL-SDR that we're calling KerberosSDR. A coherent RTL-SDR allows you to perform interesting experiments such as RF direction finding, passive radar and beam forming. In conjunction with developer Tamas Peto, we have also had developed open source demo software for the board, which allows you to test direction finding and passive radar. The open source software also provides a good DSP base for extension.
USA-Satcom is the programmer of XRIT Decoder (not to be confused with XRITDecoder by CM2ESP), which is a popular (paid) Windows decoding application for GOES weather satellites. Recently, over on the SDRplay forums RSP2user made a note about the latest update:
USA-Satcom has just released v2.1.0.0 of the XRIT Decoder. Along with enhancements for the XRIT Decoder, a new RSP Streamer X has been released and is operable with the RSP1A, RSP2, and RSPduo - new features include operation with two streams simultaneously (provided that the PC being used has sufficient processing power and an RSPduo or more than one compatible RSP are being used). Also new is the XRIT File manager which allows for improved operation with both LRIT and HRIT files, improved LUT for excellent false color images, user-selectable automated black filling of the white background on full disk visual and false color HRIT images, and country as well as state map overlays.
The new color enhancements are excellent:
GOES 16 Full Disk Weather Satellite Image. Received by RSP2user with V2.1.0.0 of XRIT Decoder.
If you are interested in receiving and decoding GOES images, we now have several previous blog posts on this topic which may be helpful.
Thank you to Giuseppe (IT9YBG) who has written in to share his tutorial about setting up a direct sampling RTL-SDR V3 based SSTV receiver on a Raspberry Pi. He writes that he uses the receiver to continuously receive images at 14.230 MHz, but with a frequency tweak in the command line code the system could also be used to receive the VHF SSTV images sent by the ISS.
In the tutorial he uses the free QSSTV software for decoding. An RTL-SDR together with the CSDR DSP software is used to set up a command line based receiver, which pipes the SSTV audio into a virtual audio sink, and then into QSSTV. The receiver setup procedure is similar to the method used in our RTL-SDR V3 QRP monitoring station tutorial, and is a very nice way of setting up an efficient command line based RTL-SDR audio output.
QSSTV Running on a Raspberry Pi with RTL-SDR V3 Radio
Recently JJ wrote in and wanted to share his multi-feature living room radio that he's created with a Raspberry Pi, RTL-SDR, and various software packages installed on the Pi. Previously we posted about his cute LegoPi radio, and this living room radio is an iteration on that.
The radio is able to tune into live broadcast FM via an RTL-SDR and the NGSoftFM software, and also can be remotely access with SpyServer. It can also tune into internet radio, or play MP3 files. He's also installed Google Assistant and Alexa onto the Pi, so it can work as a digital assistant too. The features and software he uses are noted below:
FM / DAB+ / Internet radio with random mode / MP3 player / Google assistant / Amazon Alexa / SPYserver (SDRsharp), all controlled with a USB keypad or a Bluetooth remote control.
Internet radio VLC (https://www.videolan.org/vlc/index.html) The random internet radio part is a lot of fun to use. You can do random by genre or just random everything. Reminds me when turning the MW dial at night when I was a kid and not knowing what was coming next! It is just a python script that fetch the icecast directory then populate a small SQL database on the pi. I used this (https://github.com/ksc91u/icecast_play) as a starting point.
MP3 player VLC. I used a 16GB SD card on the pi (good compromise between speed of boot versus capacity). The whole system takes a little bit less than 5GB, which means I have 10GB+ for MP3 files.
SPYserver More a gadget than a serious tool because I'm using a wire for antenna (on the last radio) but has proven to be usefull to help position the wire for optimum FM / DAB+ reception by looking at the spectrum and play with the dongle gain in SDRsharp (https://airspy.com/spy-servers/).
Bluetooth remote control I used a PlayStation 3 (PS3) bluetooth remote since the pi 3 has bluetooth built-in. Easily available in used video game stores and very cheap, the remote works very well but it took me a while to get it going. This page helped: https://www.mythtv.org/wiki/Sony_PS3_BD_Remote
Last but not least, the radio is a complete Linux environment so I can connect to it from my Win10 box via SSH (https://www.chiark.greenend.org.uk/~sgtatham/putty/latest.html) and play with all the RTL-SDR goodies, even GNU Radio :-) providing you install a desktop environment (for ex. PIXEL) on top of Raspbian Stretch Lite.
