Understanding Modern Digital Modulation Techniques
- Electronic Design magazine, 2012. Good introduction to digital modulation techniques
Morse Code by P. Lutus
- Nice page giving some theory and history of code. Has a nice text to CW converter.
Software Defined Radio
Software-Defined Radios by P. Lutus - Nice page on theory of SDRs, hardware, and software.
- A Python-based SDR by P. Lutus