1999 02 00 73 Magazine - UFO Detector

Magazine Overview

Title: 73 Amateur Radio Today
Issue: #461
Date: February 1999
Cover Headline: Monitoring Solar Mischief

This issue of 73 Amateur Radio Today delves into the fascinating world of solar activity and its impact on radio communications, alongside practical projects for amateur radio enthusiasts.

Geomagnetic Monitoring: Here Comes the Sun (Part 2)

This section, authored by Thomas M. Miller WA8YKN, continues a guide to monitoring geomagnetic effects. It highlights that while Internet data from satellites like GOES 8 and 9 is available, building personal monitoring equipment is a fun and rewarding pursuit. The article details two primary methods for detecting geomagnetic shifts:

"Earth Currents" Measurement

This method involves measuring the voltage differential between two long copper rods driven into the ground, spaced 100 feet or more apart. Changes in the geomagnetic field induce electricity in conductors, including the Earth itself. A sensitive zero-center microammeter or an auto-polarity digital multimeter set to the mV scale can be used to measure these shifts. Shielded cable should connect the rods to the meter, with the shield grounded at one end.

Compass-Based Detector

A simpler method uses a modified compass. A small hole is drilled near the rim of the compass disk at the EAST and WEST positions to allow a light beam from an infrared LED to pass through. A phototransistor below the disk detects rotation. A circuit (Fig. 1) can activate a piezo alarm when the compass disk rotates even slightly due to magnetic field shifts. This method requires only the compass disk and needle, mounted on a small board.

Magnetometer (The "UFO Detector")

An even more sensitive device is the magnetometer, originally conceived as a "UFO Detector." This instrument uses an iron rod to concentrate geomagnetic field lines. A coil of many turns of fine wire wound around the rod induces a voltage when the magnetic flux changes. This voltage is amplified and can trigger an alarm. Milled steel can substitute for iron rods, and a #10-32 bolt passed through a coil from a small relay can serve as a portable sensor. Increasing the rod size and coil turns enhances sensitivity. The article describes a highly sensitive version built with #36 magnet wire. The circuit diagram (Fig. 3) shows a dual op-amp for amplification, feeding into an LM339 comparator and a 555 timer for the alarm. An audio amplifier stage is also included, allowing detection of strange sounds, potentially preceding thunderstorms. The device can be AC powered or battery powered, with AC power being better for continuous monitoring but susceptible to line noise, while battery power is portable but limited by battery life.

Antenna Discussions

Which Antenna Is Best for You?

This article discusses the importance of antenna selection for optimal HF operation.

Really Simple 20m Antenna

A simple 20-meter antenna design is presented, featuring elements chosen not to be self-resonant but to exhibit a mean impedance of approximately 200 ohms at the feedpoint on multiple bands (80, 40, 20, 15, and 10 meters). It can be fed with open-wire line or coaxial cable. An antenna tuner may be necessary for a good match.

Multiband Antenna (Fig. 6)

Fig. 6 illustrates a multiband antenna design with specific element lengths (16.7 meters and 12.35 meters) for different band configurations (80, 20, 15, and 40, 10 meters). The article notes that while the antenna theoretically presents a 200-ohm impedance, an antenna tuner is likely needed. The author has not personally tested this design but reports positive feedback from friends who have.

Receiver and VFO Projects

Build a Dream Receiver

This article likely details the construction of a high-performance receiver for amateur radio use.

And a VFO, Too!

This suggests a companion project to build a Variable Frequency Oscillator (VFO), essential for precise frequency control in transmitting and receiving.

Review: IC-706MKII - Wow!

This section provides a review of the ICOM IC-706MKII transceiver. The review is highly positive, with the reviewer exclaiming "Wow!" indicating strong satisfaction with the radio's performance. The article notes that the upcoming G model will include 440 MHz, a progression driven by competition with new models from Yaesu and Kenwood. The reviewer expresses no personal need for the added 440 MHz band but acknowledges the trend towards more powerful, smaller radio units. The reviewer also suggests a desire for aftermarket accessories like a high/low cut audio filter and a direct frequency entry keypad.

Never Say Die

This personal anecdote recounts the author's journey from working in television production to co-founding a successful speaker system business with engineer John Karlson. The story highlights the entrepreneurial spirit and the process of developing and marketing a new product based on an antenna principle applied to speaker enclosures.

Recurring Themes and Editorial Stance

The magazine consistently promotes hands-on experimentation and building within the amateur radio hobby. There's a strong emphasis on practical projects, from monitoring natural phenomena to constructing antennas and receivers. The editorial stance appears to encourage self-sufficiency and innovation, as seen in the "Never Say Die" section and the detailed technical articles. The inclusion of a "UFO Detector" project, while potentially sensational, reflects a willingness to explore diverse interests within the broader community of radio enthusiasts, linking scientific curiosity with popular culture.