RTL-SDR for 433MHz/70cm CubeSats on GNURadio – Telecommunications, Navigation & Electronics

Introduction

In the previous post I examined receiving Amateur Radio/University CubeSats on the 433MHz/70cm band (Ref.1). In this post I look at how to decode CubeSat transmissions using the gr_satellites out of tree module on GNURadio. gr_satellites was developed by Daniel Estevez EA4GPZ. I will test several library signal captures to demonstrate how to use the software. In the next post I will do an off-air test.

gr_satellites on GNURadio

Fig.1 CubeSat Decoding with GNURadio & gr_satellites

Daniel’s GitHub page is a good start to get into the software (Ref.2). There is a folder for satellite-recordings which we can use to test the software. There are also several YouTube presentations such as the one to AMSAT-UK (Ref.3). I summarize some of the important points:

-Command Line
-Output packets in hex or parsed telemetry
-282+ satellites/53+ protocols
-Real UDP float32 48Ksps
-Input Conventional Rx/SDR or WAV files
-Input Gqrx UDP stream/WAV files
-FMdemod or USB
-USB_narrow_0-3KHz_fc@1.5KHz/USBwide_0-24KHz_fc=12KHz

There is excellent documentation available (Ref.4). The module can be installed in several ways. I installed GNURadio using Radioconda which includes gr_satellites as one of many packages (Ref.5). Figure 1 shows my basic setup.

Signal Captures – satellite-recordings

To get a feel for the software we can run one of the saved WAV files in the satellite-recordings folder. I created a folder in c:\cubesat where I placed a copy of ao73.wav. In the documents section Figure 2 it gives you all the details of this supported satellite. Figure 3 shows the command line to decode this wav file and decoded telemetry.
gr_satellites FUNcube-1 –wavfile ao73.wav

Signal Captures – EIRSAT-1

Fig.4 Supported Satellites EIRSAT-1 Data

In my previous post I was looking to decode a currently launched CubeSat. I decided to track EIRSAT-1. This satellite is fortunately in the Supported Satellites list as show in Figure 4. EIRSAT-1 is well documented and has it’s own github page. Sample recordings are available there (Ref.6). Figure 5 shows a list of these recordings and Figure 6 is a decode of the second to last wav file.