The March/April issue of QEX is coming soon, and it is full of theoretical and practical technical articles that you won't want to miss.

Joel Harrison, W5ZN, and Bob McGwier, N4HY, describe the "Design, Construction and Evaluation of the Eight Circle Vertical Array for Low Band Receiving." Even if you don't have enough real estate to build one of these, it is fun to read about this steerable array for 160 or 80 meters. Jon Wallace continues with his "Amateur Radio Astronomy Projects." In this installment, Jon takes us on an amazing ride into the world of whistlers, tweeks, sferics and other types of natural radio signals. Learn how to receive these 10 to 20 kHz VLF signals and display them on a computer using a spectrogram program.

Paul Wade, W1GHZ, concludes his series on "Waveguide Filters You Can Build and Tune" with "Part 3 -- Evanescent Mode Waveguide Filters." It's a must read for UHF and microwave enthusiasts! Chuck McConaghy, WA6SYE, shares an Amateur Radio project he developed for another of his hobbies: model rocketry. Chuck uses "Doppler Tracking" techniques to record signals from his rockets and analyze data such as speed and engine burn times and to calculate maximum height. He can even track the RF signal from a wayward rocket after it lands.

John E. Post, KA5GSQ, describes his experiments "On Maximizing the Tuning Range of SA/NE 602 IC Colpitts Oscillators." John presents theoretical and experimental data for MF, HF and VHF oscillators, and offers an Excel spreadsheet to calculate optimized component values for your design frequency. Robert K. Zimmerman, VE3RKZ, presents "An Inexpensive HF Power Meter with a Linear dB Scale." Bob's approach uses the laser diode from a dollar store laser pointer as an RF sensor and a cadmium sulfide photo detector to drive the meter.

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