(Parte 1 de 2)

GeotechPage 1

P o pula r E l e c tron

Ma y 1978 -- Copy righ t

Ge rns b a c k P ubli s hing

, re p r oduc e for pe o nal use o n ly

Over the past 30 years, thousands of

UFO sightings have been reported to and investigated by government and scientific researchers. Most have been readily attributed to such things as aircraft, the planets, meteors, and luminescent swamp gas. A small but significant number of incidents remain unexplained. The possible extraterrestrial nature of UFOs therefore is still an open question.

Common to many reported UFO incidents are magnetic disturbances which affect compasses, auto speedometers, electric power meters, etc. Presented in this article are various types of sensing circuits which will detect such magnetic anomalies. The circuits are inexpensive to build and use readily available parts and materials. Their use, however, is not limited to amateur UFO investigations. These magnetometers will be of interest to anyone who wants to explore magnetic phenomena, and students take note make fine Science Fair projects.

All the magnetic-detection systems presented here employ audio and/or visual intrusion alarms.

Home Magnetometers.

Although professionals monitor magnetic fields with such sophisticated devices as proton free-precession magnetometers, good results can be obtained using the inexpensive homebuilt magnetometers described here. These devices have low power consumption and can be battery- powered for lengthy periods. Although they have less sensitivity than the proton magnetometer, which measures the precession (wobble) of protons in the presence of a magnetic field, the inertia-less CRT and electro-induction magnetometers are faster by a factor of about 1,0.

Sky Magnetometer.

Shown in Fig. 1 is a field-induction magnetometer designed to have its sensor mounted on the exterior of a building. Two separate detection principles are employed. The high-speed sensor, shown schematically in Fig. 1A and photographically in Fig. 2, is of the electromagnetic induction type. The actual sensor is comprised of a 2’ (61- cm) long mu-metal (a soft iron alloy) bar that serves as a flux concentrator for the coils. The larger of the two coils (L1) is a 10,0-ohm coil slipped over the bar and positioned at its center. Inductor L2 consists of 30 turns of No. 24 enamelled wire wound over the main coil. Coil L2 is used to induce a voltage across L1 for testing. Signals induced across L1 are amplified by emitter follower Q1 (Fig. 1B). (Transistor Q1 is a Darlington pair with a beta of at least 12,0.)

When IMPULSE TEST switch S1 is depressed, capacitor C1 discharges through potentiometer R3 and coil L2, inducing a current pulse in main sensing coil L1. Potentiometer R2 is used to adjust the sensitivity threshold. The amplified current pulse is indicated on meter M1 and can be passed to a paper chart recorder via resistor R9.

The current pulse at the emitter of Q1 is also passed via TRIGGER LEVEL control R7 to the gate of SCR1. When SCR1 fires, it activates alarm Al. Because the power source is dc, Al will remain on even after the triggering signal has passed. Normally closed RESET pushbutton switch S2 must be momentarily depressed to silence the alarm.

Operating power is obtained from a conventional line-operated, regulated 9- volt dc supply. If line power should fail, relay K1 automatically switches to B2, a back-up battery supply.

TRIGGER ADJUST control R7 should be set to prevent the alarm from being triggered during lightning storms. Meter M1 is not critical, but it should be able to indicate the triggering threshold for the SCR, which is about 0.8 mA. A

A variety of home-built detectors to indicate magnetic disturbances such as those reported to accompany UFO sightings

GeotechPage 2

P o pula r E l e c tron

Ma y 1978 -- Copy righ t

Ge rns b a c k P ubli s hing

, re p r oduc e for pe o nal use o n ly superimposed current of about 50 µA, the output of L1 amplified by Q1, will trigger the magnetometer. Near-trigger conditions can be observed on the meter, providing a built-in test facility in addition to L2.

The instrument’s construction and packaging, including the external sensor shown in Fig. 2, are not critical. The flux concentrator and coils can be protected from the elements by a length of magnetically neutral PVC plastic pipe, supported by aluminum brackets. The upper part of the sensor is enclosed in a glass or plastic container which can house another (optional) sensing coil made from an automotive ignition coil with its metal shield removed to provide full magnetic exposure.

The lower end of the pipe contains the electrical connections to the coils and is also protected by a glass or plastic enclosure. Connections between the coils and electronics console are made via shielded cables that pass through the support structure. Ground the cable shields to a true earth ground to avoid the danger of lightning strikes.

Compass Magnetometer.

The second sensing system comprises a compass-needle assembly arid a geared compass of the automotive or marine type and is used for detecting slow magnetic field variations. The compass-needle assembly is shown in Fig. 3A. The primary sensor is a 6 (15.2-cm) magnetic needle mounted on a low-friction agate bearing. Two equally balanced opaque paper extensions are attached to the needle.

Once the magnetic needle settles down to a stable state, optical coupler OC1 must be positioned so that one of the opaque paper extensions fits into the narrow gap of the module. This module consists of a LED and a Darlington phototransistor, the two separated by a narrow gap into which the opaque paper extension is fitted. When the paper is in the gap, the light path is interrupted. This approach affords contact-less and friction-free sensing of the needle’s motion, and can also be used with meter pointers, cursor devices, eddy-current disks and mechanical indicators.

As shown in Fig. 3B, potentiometer

R1 and current-limiting resistor R2, determine the light output of the LED in the pickup assembly. Only a minimal amount of LED output is required.

With the LED illuminating the phototransistor, the potential between Q1 pins 3 and 4 is typically about one volt. Comparator IC1 is wired so that its output is high when the light path inside OC1 is blocked, and goes low when the motion of the magnetic needle moves to allow an uninterrupted light path. Since IC1 is powered by a 5-volt supply, its output is TTL compatible. If desired, the output from IC1 can be used to power a relay (K1). Because the voltage comparator used is limited to a 20 mA output, the coil resistance of the relay must be at least 250 ohms.

If desired, the compass needle can be mounted vertically so that it dips up and down in the presence of a magnetic anomaly or disturbance.

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P o pula r E l e c tron

Ma y 1978 -- Copy righ t

Ge rns b a c k P ubli s hing

, re p r oduc e for pe o nal use o n ly

CRT Detector.

The inertia-less cathode-ray tube instrument shown in Fig. 4 is an extremely sensitive, high-speed magnetometer. Professional CRT magnetometers can measure extremely weak magnetic fields. The sensitivity of these CRT detectors exceeds that of both nuclear and rubidium-vapor magnetometers by a factor of two to four. However, commercial CRT systems are very expensive. This forces the experimenter to fashion a home-brew CRT magnetometer such as that shown in Fig. 4. The display speed of this system is contingent only on the signal transfer time of the electronics package.

The CRT can be obtained from an oscilloscope or similar instrument. It should be an electrostatic -- not electromagnetic -- system. Because the CRT must be operated 30’ (9.lm) or more from its parent housing, lengthy cables are required to deliver the filament, centering, focus, and high voltages.

Attached to the glass faceplate of the

CRT is light-dependent resistor LDR1 and an opaque mask with a tiny aperture cut in it. The size of the aperture should be about the same diameter as the focused spot on the CRT screen. The photocell/aperture mask assembly should be secured to the center of the CRT’s faceplate in an opaque retainer cup. Do not use a permanent cement when attaching this assembly to the CRT because it may have to be moved somewhat if a phosphor burn (dark spot) develops on the screen.

The CRT must be operated without any type of shielding and should be supported by a nonmagnetic structure. Use well-insulated cables for the various CRT operating potentials. Set the brightness to produce a relatively low intensity spot, and then focus the spot. Using the horizontal and vertical centering controls, position the spot directly in the hole in the aperture mask. You can tell when the spot is properly positioned with the aid of an ohmmeter. Connect the meter across the leads of the photocell and operate the centering controls. The photocell’s resistance will be very low when the spot is properly positioned.

When LDR1 is illuminated, the circuit in Fig. 4B causes K1 to close, applying power to READY lamp I1. If for any reason the CRT’s beam moves away from the small aperture, K1 will momentarily de-energize and extinguish I1. This triggers an alarm circuit

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P o pula r E l e c tron

Ma y 1978 -- Copy righ t

Ge rns b a c k P ubli s hing

, re p r oduc e for pe o nal use o n ly composed of SCR1 (whose gate is protected by D3) and audible alarm Al. Even if the beam returns to the aperture in the mask, the alarm will continue to sound until RESET switch S1 is momentarily depressed to interrupt the dc path through SCR1. Diode D2 protects transistor Q3 from voltage transients generated by K1 during switching.

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