QEX -- The July/August Issue
The July/August issue of QEX is coming soon, and it is full of theoretical and practical technical articles that you won’t want to miss. QEX is the ARRL’s “Forum for Communications Experimenters.” Published bimonthly, it features technical articles, columns and other items of interest to radio amateurs and communications professionals. The mission of QEX is threefold: To provide a medium for the exchange of ideas and information among Amateur Radio experimenters; to document advanced technical work in the Amateur Radio field, and to support efforts to advance the state of the Amateur Radio art.
Dick Jansson, KD1K, explains the operation of “Heat Pipes” as cooling technology, especially as it was used on the AMSAT-OSCAR 40 satellite. Heat pipe cooling systems are showing up in today’s computers, and Jansson suggests that we might be able to use these devices for cooling the transistors in solid state amplifiers. Oleg Skydan, UR3IQO, examines “True TLT H-Mode Mixers.” These switching mixers use transmission line transformers rather than conventional transformers. Skydan provides the details for this improved mixer scheme, in which he achieved third order intercept point (IP3) performance on the order of +40 dBm or above across the HF range.
Jim Koehler, VE5FP, describes his experiments with “The Shunt Method for Crystal Parameter Measurement.” His technique provides a reliable, accurate way to measure crystal Q, motional resistance, Rm, and parallel capacitance, CP. Harold Kinley, WA4GIB, describes how to solve several impedance matching problems by using Nathan Iyer’s free Smith Chart computer program in “Using QuickSmith -- Part 1.
Robert Zimmerman, VE3RKZ, describes one of his antenna experiments in “A 20 Meter Sleeve Dipole Without the Sleeve.” He uses a feed line choke consisting of a coaxial cable coil and a resonating capacitor at one end of the dipole to block antenna current from flowing back down the outside of the shield. Since the coaxial cable feed line comes into one end of the dipole, this antenna looks like an end-fed wire.
Jon Wallace describes another “Amateur Radio Astronomy Project.” This time we learn about his “Total Power Radio Telescope,” as he describes the hardware he built to create a radio map of the sky -- after 10 years of data collection! Dick Kolbly, K6HIJ, reviews Tom Y. Otoshi’s book, Noise Temperature Theory and Applications for Deep Space Communications Antenna Systems. Kolbly points out that this book title may not sound like it would be of much interest to Amateur Radio operators, but it contains a wealth of information for microwave weak signal experimenters.
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