A spectrum analyzer for the radio amateur

Demonstrates the construction of a homebrew spectrum analyzer designed by Wes Hayward, W7ZOI, and Terry White, K7TAU, enabling radio amateurs to build a capable test instrument without significant expense. The resource details a double-conversion superheterodyne circuit, employing intermediate frequencies of 110 MHz and 10 MHz, and covers essential blocks such as the time base, logarithmic amplifier, resolution filters, and local oscillators. It highlights the use of hybrid and monolithic ICs, including mixers, amplifiers, and VCOs, to simplify construction while maintaining performance. The design supports useful measurements in the 50 kHz to 70 MHz range, with methods outlined for extending capabilities into VHF and UHF.

The authors emphasize that this analyzer, while simple to build, is intended for serious measurements, requiring careful control of signal levels to avoid spurious responses. It uses an oscilloscope for display, with specific instructions for calibration and adjustment of various stages, including the log amplifier and IF gain. The guide provides detailed schematics and component lists for each section, such as the 110 MHz triple-tuned band-pass filter, which achieved 90 dB image rejection, a significant improvement over double-tuned circuits. Practical advice on alignment and troubleshooting is included, drawing on the authors' extensive experience in RF circuit design.