At our July monthly membership meeting, SPARC welcomed Carl Luetzelschwab K9LA, an expert on the science of radio propagation. Professionally, Carl worked for forty-one years as an RF design engineer, and in his spare time he was a columnist for WorldRadio (and later CQ) beginning in 1997. He continues to write a monthly column on radio topics at his personal website. His presentation to our July meeting is linked below (2 MB PDF). SPARC thanks Carl for speaking with us and for his continued devotion to the hobby!