Just ran across a book that I can highly recommend for amateur radio astronomers and for time nuts, as well as those interested in using GNU Radio for signal analysis: Signals and Systems For Dummies 1st Edition by Mark Wickert (Author) There are some on Amazon for as little as $5.00 used. You'll need some math to get the best out of this book, but it has a serious engineering oriented approach and can be used as a reference as well as a tutorial. Clearly written and Highly recommended by me at least. YMMV as usual. Don ----------- "It's always something." Roseanne Rosannadanna ----------------------" Dr. Don Latham AJ7LL PO Box 404, Frenchtown, MT, 59834 VOX: 406-626-4304