Qt-FT8 is a separate program dedicated to decoding FT8 messages transmitted in the various radio amateur bands.
For Linux (x64) an AppImage is available, for Windows an installer.
- Introduction
- Supported devices and selecting a device
- Tuning and presets
- Setting parameters for the search process
- Saving messages
- Using the pskReporter
- Generating an executable
- Copyrights
FT8 transmissions consist of short encoded messages, transmitted on defined regions within different amateur bands.
This FT8 decoding program - when running - shows a main widget - one with the controls, a device control widget and a widget for preset frequencies.
The program is written in C++ and uses Qt (version 6) and qwt (6.2) for the GUI.
To ease use, precompiled versions (a Windows installer and an AppImage for x64 based Linux boxes) are available.
For generating an executable, see the relevant section of this README
The main widget consists on three parts, at the top section the controls, in the middle a spectrum display, and at the bottom a widget showing received messages.
Received messages can be saved into a file, and sending them to the so-called pskReporter is possible.
Notice that since most of the transmissions are in the frequecy range until 30 Mhz, RTLSDR devices (i.e. DABsticks) are not capable of handling these frequencies, nevertheless by default DABsticks are configured in.
Once a device is selected, the software reads in samples from the device, and continuously tries to detect and decode FT8 messages. The results are shown on the bottom part of the main widget.
Qt-ft8 supports
- SDRplay devices, both with lib 2.13 as 3.XX support;
- hackrf devices;
- DABstick, but V3 DABsticks will only work from 24 MHz upwards;
- an spyServer client, configured for 8 bits RTLSDR byte encoding.
On program startup, a small widget is shown for device selection as shown below.
Selecting a device is )obviously) by clicking on the name of the device in the list. Note, however, that for the SDRplay devices (both Windows and Linux), one should install the support libraries from SDRplay.com
While the Windows installer provides support for the DABsticks and the HACKrf devices, the AppImage does not. One needs to install driver software first.
A recent addition is the client for the spyserver. Since my antenna equipment is limited, I - from time to time - connect to a - relatively nearby - spyServer, one that supports the AIRspyHF.
The client asks for a datastream of 96000 8bit IQ samples, that works well, as the picture on top shows.
The top line of the main widget has four selectors:
- the most left one, labeled select freq when touched shows a small widget with a keypad.
The keypad (picture above) can be used to specify a frequency. Touching the "Khz" button passes the selected freq - as KHz values - on to the system, touching the "Mhz" button as MHz values.
The selected frequency can be modified by clicking on the spectrum display, or - for small modifications - with the mousewheel. The frequency step per click of the mousewheel is determined by the spinbox on the top line, default value is 5 Hz.
Since the frequencies om which FT8 messages are transmitted are predefined, it is useful to have some presets, Qt-FT8 has therefore a preset list. This list of presets can be made visible (or hidden) by touching the button labeled presets (picture below).
Selecting a frequency from the preset list is simply by clicking on it.
- touching the button labeled frequency save adds the currently selected frequency to the list of presets. Removing a frequency from the preset list is also possible, double clicking on the element in the list.
On initial program startup the list of presets is filled with a limited number of known frequencies. As said above, frequencies can be added to and removed from the list. The list will always be ordered.
The list itself will be maintained between program invocations as an ".xml" file in the user's homedirectory.
The spectrum display shows the 96000 Hz wide frequency range, centered around the selected frequency. On clicking with the right mouse button the display switches between a regular spectrum view and a waterfall view.
Two parameters can be set (or altered) for searching FT8 messages in the incoming sample stream. The third line on the main widgets shows some selectors:
-
the spinbox left, current value 20, specifies the number of iterations done when the program feels that there is data;
-
the spinbox next, current value 4000, specifies the **search width **, i.e. the region with the selected frequency in the center, where the software is searching for potential FT8 mesagges.
For both selections it (obviously) holds that higher values requires more processing effort.
- the selector labeled "All items" let you choose between searching for - as the name suggests - all items, or just CQ messages.
The button labeled "saving" on the third row of the main widget allows selecting an output file for saving the received messages in a textual form.
Format is such that with e.g. LibreOffice Calc a decent overview is obtained.
Messages can be send to the so-called pskReporter. Before sending it is required to have the identity filled in. Touching the button labeled id (fourth row of the main widget) shows a small widget where one can enter its callsign etc (an example is given below, (Of course, the identity info is maintained between program invocations).
Assuming an idenitity is known to the system, touching the button labeled Recorder prepares the system to send (unique) messages to the psk reporter and it will start up the pskReporter website as shown on top of this README.
Filling in the identity in the identity field in the top line of the web page (and touching the "go" button) shows the identifications of the transmitters of received messages on the map, as shown in the figure on top.
While for both Linux (x64) and Windows precompiled versions are available it is of course possible to build an executable yourself.
The directory contains a file "qt-ft8.pro" that can be used to generate a Makefile. In order to do so, Qt6 and qmake6 need to be installed.
The AppImage is built on Ubuntu 20, the required libraries and programs can be installed as given below
- sudo apt-get update
- sudo apt-get install git
- sudo apt-get install cmake
- sudo apt-get install build-essential
- sudo apt-get install g++
- sudo apt-get install pkg-config
- sudo apt-get install libfftw3-dev
- sudo apt-get install zlib1g-dev
- sudo apt-get install libusb-1.0-0-dev
- sudo apt-get install mesa-common-dev
- sudo apt-get install qt6-base-dev
- sudo apt-get install qt6-multimedia-dev
- sudo apt-get install libsamplerate0-dev
While on my development box (Fedora) a Qt6 and qwt-6.2 version are available from the repositories, Ubuntu (20) does not provide these.
- Download qwt-6.30 from "https://sourceforge.net/projects/qwt/files/qwt/6.3.0/";
- follow the instructions (i.e. unzip, cd to the unzipped folder) and adapt the config file to your likings;
- building is then simple (takes some time though): "qmake6 qwt.pro", "make";
- install the library ("sudo make install") and inform the loader "sudo ldconfig";
- Note that the default for installation is "/usr/local/qwt/6.3.0", adjust the PATH settings accordingly.
Copyright (C) 2022 .. 2025
Jan van Katwijk ([email protected])
Lazy Chair Computing
Copyright of libraries used - Qt-DAB, qwt, fftw,
libsamplerate, libusb-1, - is gratefully acknowledged.
Some functions in the core of the decoder, in particular
the ldpc decoding, is - with minor modifications -
taken from Karlis Goba.
All rights of Karlis Goba is gratefully acknowledged.
Qt-FT8 - the sources and the precompiled versions -
is distributed under e GPL V2 library, in the hope that
it will be useful, but WITHOUT ANY WARRANTY; without even the
implied warranty of MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE. See the GNU General Public License for
more details.