Rud, a very good (and _free_) book is available online at http://www.dspguide.com It is at an introductory level, as you seem to need.
A good discussion group is comp.dsp on usenet, though not always the gurus there are so willing to answer to basic questions. But trying costs nothing... About libraries to compute FFTs, what I use in my programs is the Intel Signal Processing Library, which is free for non commercial applications. It is very fast, being coded in hand-optimized assembler language. Otherwise another good library is FFTW ( http://www.fftw.org ) 73 Alberto I2PHD ---------------------------------- > I want to experiment with digital protocols in ham radio by starting > with the PC soundcard. I understand some of the basics like filters > and FFT. I even have some of them working in code (C++). > > I do not know how to proceed from the basics into demodulating an > audio signal into bits. > > For instance, I am playing with the VHF packet protocol which use 1200 > and 2200 hz signalling. I enter the samples for a single 1200 hz cycle > into the FFT array. The FFT shows a peak at around 1000 hz. The FFT > array is 2048 samples long filled with 0s except for the 1 cycle of > 1200 hz which is 40 samples at the rate of 48000 samples per second. > If I put 4 cycles in the FFT array I get 1195 hz which is correct. > Hanning or Hamming Windows do not help. > > I have looked at some of the available source but am missing the > insight I need for proceeding further. Any suggestions on how to > proceed further? Any suggestions on books or web sites that address > communications DSP at this level? How about an email reflector where I > can ask questions of DSP gurus? > > -73- > Rud K5RUD > ARES AEC > Montgomery County, TX > > > > ------------------------------------------------------------------------ > YAHOO! GROUPS LINKS > > * Visit your group "soft_radio > <http://groups.yahoo.com/group/soft_radio>" on the web. > > * To unsubscribe from this group, send an email to: > [EMAIL PROTECTED] > <mailto:[EMAIL PROTECTED]> > > * Your use of Yahoo! Groups is subject to the Yahoo! Terms of > Service <http://docs.yahoo.com/info/terms/>. > > > ------------------------------------------------------------------------ > > . Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/soft_radio/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
