Hello I did write a piece of software under Linux for use with the elektor kit (may 2007). Being a programmer rather than a radio-man, I had (and have) to learn a lot on signals and processing. Currently my software works well, written in C++, using qt4 for the gui, using hamlib for the rig interface and using portaudio for interfacing the soundcard. The basic configuration handles analog modes (am, fm, usb, lsb), rtty, psk, navtech, mfsk fairly well. An attempt to decode cw is implemented, letting the user set relevant parameters, it is working, however should be made more intelligent. I am working to understand olivia and included the open source implementation, but it needs quite some work before releasing.
The front end reads samples (standard 96K), the band filter is selectable in terms of bandwidth, positioning in the positive half of the field, as well as in terms of kind. Currently IIR filters as butterworth etc are implemented, as well as FIR filters (with 255, 511 filterelements, so fairly sharp) and FFT convolution implementations of the FIR filters. The inputrate can be selected. The backend runs with a lower rate (also selectable), and does the decoding. The user interface has spectrum and waterfall displays (front end for the whole 96K, backend depending on the selected decoding mode). The implementation is straightforward and was a very nice programming exercise (first program in about 8 years). It could benefit from more advanced techniques for handling and improving the signals at various stages during processing and that is where I need input from this group. Another field where I could use some input is in descriptions for varieties of digital modes. The elektor kit does work (not very sensitive though), I am thinking on another board (but preferably cheap), but the main concern is the software. Obviously, the software is under the GPL available for interested parties. all the best, waiting for reactions jan
