This satellite carries a store & forward packet bulletin board which works according to the PacSat protocol. This protocol and its implementations have been in use since the late 1980s, although its popularity has been in decline since the internet became mainstream. There is mainly legacy software available, like the WiSP suite (Windows Satellite Program), written in the Windows XP/NT4 era. In 2018 Chris (G0KLA / AC2CZ) wrote a more modern replacement for WiSP, written in Java, which means it can run be on various OS platforms (Windows/Linux/Apple). On this page I document how to install and use this program called PacSat Ground Station on a Linux installation.



To get a working system (receiving/transmitting) you will need the following:

  1. A transceiver capable of receiving and transmitting 9600 baud digital signals, or a transceiver capable of transmitting 9600 baud digital signals in combination with an SDR receiver.
  2. The necessary physical connections between the transceiver and the PC: audio in/out and PTT.
  3. A Linux box with the following pieces of software...
  • Gpredict, used for satellite tracking
  • GQRX, in case you use an SDR receiver
  • Rigcrl, which you can find in the libhamlib-utils package
  • Direwolf, which is the soundmodem/Packet Engine (PE)
  • PacSat Ground Station (PSGS for short)

Warning: I will assume you are familiar with Linux, installing software and using the command line.


Setup described on this page

For satellite reception I mainly use an SDR receiver (Airspy Mini). I will therefore describe the setup using an SDR for reception and a transceiver for transmitting. This is a diagram of my current setup in order to work Falconsat-3.

For Linux distribution I use Debian based Kubuntu and the examples and screenshots on this page are done using version 19.04.


Installing the necessary software

Gpredict and GQRX are installed from the Kubuntu repositories. For installing Direwolf we need to install Git first. To control the receiver we need libhamlib-utils.

$sudo apt-get install gpredict gqrx-sdr git libhamlib-utils

Kubuntu 19.04 has an older version of Direwolf in its repository (v1.4), which will not work full duplex, therefore it will need to be installed from source (v1.5).

$git clone http://github.com/wb2osz/direwolf
$cd direwolf
$sudo make install

Direwolf will now be installed in /usr/local and can be started from the command line.

Make sure that Gpredict and GQRX are working before going on.


Setting up the receiving end

When setting up Gpredict you will have to add your ground station details and add a module for Falconsat-3 (check the Gpredict manual on how to do this). To make Gpredict control GQRX go to Edit 🠚 Preferences 🠚 Interfaces, and add a new radio interface. Enter the information according to the screenshot.

When you click on the downward arrow in the Gpredict module for Falconsat-3 you can access the Radio Control panel and GQRX will already be selected as receiver.

Make sure GQRX has been started, then click on Track and Engage and this makes Gpredict take control of GQRX. If Engage doesn't stay selected it means remote control in GQRX is not activated yet. Go to the GQRX main window, select Tools and put a check mark before Remote Control. Also go to the Remote Control Settings and check if the port number is set to 7356.

After this Gpredict can take control of GQRX when Engage is depressed and it will track, and apply Doppler correction to, the Falconsat-3 signal. Also depress the UDP button in GQRX, after which GQRX will stream the audio received over the UDP port. Check if this port is set correctly by depressing the button with the three dots to the right of the UDP button, then selecting "Network". UDP host should be reading "Localhost" and UDP port should be set to 7355

To be continued