Featured AMRAD articles
- The Spread Spectrum Sourcebook by Andre Kesteloot
American Radio Relay League | 1991 | ISBN: 0872593177 | 385 pages | File type: PDF | 13.6 MB
It is safe to say that amateur spread spectrum exists because of one unique entity-the Amateur Radio Research and Development Corporation. Based in the Washington, DC area, AMRAD played a key role in the development of amateur packet radio in the early 1980s, and is continuing to lead the way in the realm of amateur spread spectrum. Its members are dedicated to furthering the Amateur Radio art, and their accomplishments speak for themselves.
From the foreword by David Sumner, K1ZZ:It is altogether fitting, therefore, that this book be edited by long-time AMRAD President Andre Kesteloot, N4ICK. He has done as much as anyone to spread the word about the intriguing intricacies-and very real benefits-that spread spectrum systems hold for the amateur service. The League is proud to be associated with AMRAD's efforts to bring practical spread-spectrum systems to the amateur bands. This book brings together articles, papers and documents that provide an overview of how amateur spread spectrum evolved from a short notice in the AMRAD Newsletter. This newsletter provided the bulk of the early material on spread spectrum, but it wasn't long before QST and its then-new experimenter's newsletter, QEX, took up the cause. Nearly all the spread spectrum articles published in those three sources are reprinted in this book, as are the regulatory documents that made spread spectrum legal on the amateur bands. Toward the end of the book, two ground-breaking technical papers are published in their entirety. Overall, the book leaves little doubt that it's only a matter of time before the spread spectrum techniques become well established in the amateur service.
AMRAD is grateful to the ARRL, the holder of the copyright, to allow AMRAD to make the entire book available in pdf format. Download 13.6 MB
Click on the links to download pdf files for these AMRAD Newsletter articles:
- A Review of Basic Error Correction Codes by Hal Feinstein, WB3KDU
Abstract: An Error Correcting Code (ECC) is a system of parity checks that can detect and correct errors that corrupts data during transmission. Claude Shannon developed information theory during World War II. After the war he worked at ATT Bell Labs where he developed the basic idea of detecting errors and fixing them by cleverly using parity bits that were transmitted along with the data. Shannon called the different patterns of parity data a code. He developed a way to measure how good a code was and found a critical boundary for code quality, today called the Shannon limit. Shannon discovered no code could be better than this limit but he did not discover what pattern of parity bits created the best code. In other words, the code would have to be discovered through invention and testing; the application of imagination and pure creativity.
- Matching Electrically Short Antennas by R. C. Hanson
Abtract: A number of steps can be taken to improve the performance of short dipoles, but not all are equally helpful. Series loading with resistance or inductance, and top-hat (capacitive) loading have all been used. The idea behind each of these is to make the current on the dipole more nearly constant, thus increasing the radiation resistance by as much as a factor of four. For series loading, the location of the load involves a tradeoff between input resistance and load inductance. These methods are widely used in mobile antennas, most often monopoles operating against ground, and the Q of the coil has a major effect on efficiency.