I have been trying for some time to get one sound-based application running. The application is soundmodem http://www.baycom.org/~tom/ham/soundmodem/ and is foundational to linux ax25 and ham radio applications. Its simplest configuration is to connect the audio from a ham radio to the mic input. Soundmodem will demodulate the binary data from the audio stream. Soundmodem has been around for many years and is mature and is known to work on older linux distributions. I have tried 3 different laptops with Ubuntu 8 and 9, and Fedora 10 and 11. I have the same difficulty on all attempts. I can hear the audio, I can mix/change the audio level, and I can display the audio waveform using the built in oscilloscope. Occasionally it will detect the carrier but soundmodem will not decode any audio data. I have saved a screenshot here http://www.freesql.org/soundmodem.png and you can see evidence of some kind of digital pulse train that is corrupting the audio stream. Could this be a configuration problem relating to sampling? I do know that soundmodem uses /dev/dsp and I start the app using padsp, also it reports that its sampling rate is 9600. Thx for any help or info, I'm really interested in getting this working. Gary H. KB1QOJ
