Geotech Page 1

Pop

ular

Ele

ctro

nics

, May

197

8 --

Cop

yrig

ht

Ger

nsba

ck P

ublis

hing

, rep

rodu

ce f

or p

erso

nal u

se o

nly

Over the past 30 years, thousands ofUFO sightings have been reported toand investigated by government and sci-entific researchers. Most have beenreadily attributed to such things as air-craft, the planets, meteors, andluminescent swamp gas. A small butsignificant number of incidents remainunexplained. The possible extraterres-trial nature of UFOs therefore is still anopen question.

Common to many reported UFO inci-dents are magnetic disturbances whichaffect compasses, auto speedometers,electric power meters, etc. Presented inthis article are various types of sensingcircuits which will detect such mag-netic anomalies. The circuits areinexpensive to build and use readilyavailable parts and materials. Their use,however, is not limited to amateur UFOinvestigations. These magnetometerswill be of interest to anyone who wantsto explore magnetic phenomena, andstudents take note make fine ScienceFair projects.

All the magnetic-detection systemspresented here employ audio and/orvisual intrusion alarms.

Home Magnetometers.Although professionals monitor mag-

netic fields with such sophisticated

devices as proton free-precession mag-netometers, good results can beobtained using the inexpensive home-built magnetometers described here.These devices have low power con-sumption and can be battery- poweredfor lengthy periods. Although they haveless sensitivity than the proton magne-tometer, which measures the precession(wobble) of protons in the presence of amagnetic field, the inertia-less CRT andelectro-induction magnetometers arefaster by a factor of about 1,000.

Sky Magnetometer. Shown in Fig. 1 is a field-induction

magnetometer designed to have its sen-sor mounted on the exterior of abuilding. Two separate detection princi-ples are employed. The high-speedsensor, shown schematically in Fig. 1Aand photographically in Fig. 2, is of theelectromagnetic induction type. Theactual sensor is comprised of a 2’ (61-cm) long mu-metal (a soft iron alloy)bar that serves as a flux concentrator forthe coils. The larger of the two coils(L1) is a 10,000-ohm coil slipped overthe bar and positioned at its center.Inductor L2 consists of 30 turns of No.24 enamelled wire wound over the maincoil. Coil L2 is used to induce a voltageacross L1 for testing. Signals induced

across L1 are amplified by emitter fol-lower Q1 (Fig. 1B). (Transistor Q1 is aDarlington pair with a beta of at least12,000.)

When IMPULSE TEST switch S1 isdepressed, capacitor C1 dischargesthrough potentiometer R3 and coil L2,inducing a current pulse in main sens-ing coil L1. Potentiometer R2 is used toadjust the sensitivity threshold. Theamplified current pulse is indicated onmeter M1 and can be passed to a paperchart recorder via resistor R9.

The current pulse at the emitter of Q1is also passed via TRIGGER LEVELcontrol R7 to the gate of SCR1. WhenSCR1 fires, it activates alarm Al.Because the power source is dc, Al willremain on even after the triggering sig-nal has passed. Normally closed RESETpushbutton switch S2 must be momen-tarily depressed to silence the alarm.

Operating power is obtained from aconventional 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 R7should be set to prevent the alarm frombeing triggered during lightning storms.Meter M1 is not critical, but it should beable to indicate the triggering thresholdfor the SCR, which is about 0.8 mA. A

BY L. GEORGE LAWRENCE

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

Geotech Page 2

Pop

ular

Ele

ctro

nics

, May

197

8 --

Cop

yrig

ht

Ger

nsba

ck P

ublis

hing

, rep

rodu

ce f

or p

erso

nal u

se o

nly

superimposed current of about 50 µA,the output of L1 amplified by Q1, willtrigger the magnetometer. Near-triggerconditions can be observed on themeter, providing a built-in test facilityin addition to L2.

The instrument’s construction andpackaging, including the external sen-sor shown in Fig. 2, are not critical. Theflux concentrator and coils can be pro-tected from the elements by a length ofmagnetically neutral PVC plastic pipe,supported by aluminum brackets. Theupper part of the sensor is enclosed in aglass or plastic container which canhouse another (optional) sensing coilmade from an automotive ignition coilwith its metal shield removed to pro-vide full magnetic exposure.

The lower end of the pipe containsthe electrical connections to the coilsand is also protected by a glass or plas-tic enclosure. Connections between thecoils and electronics console are madevia shielded cables that pass through thesupport structure. Ground the cableshields to a true earth ground to avoid

the danger of lightning strikes.

Compass Magnetometer. The second sensing system com-

prises a compass-needle assembly arid ageared compass of the automotive ormarine type and is used for detectingslow magnetic field variations. Thecompass-needle assembly is shown inFig. 3A. The primary sensor is a 6(15.2-cm) magnetic needle mounted ona low-friction agate bearing. Twoequally balanced opaque paper exten-sions are attached to the needle.

Once the magnetic needle settlesdown to a stable state, optical couplerOC1 must be positioned so that one ofthe opaque paper extensions fits into thenarrow gap of the module. This moduleconsists of a LED and a Darlington pho-totransistor, the two separated by anarrow gap into which the opaque paperextension is fitted. When the paper is inthe gap, the light path is interrupted.This approach affords contact-less andfriction-free sensing of the needle’smotion, and can also be used with meter

pointers, cursor devices, eddy-currentdisks and mechanical indicators.

As shown in Fig. 3B, potentiometerR1 and current-limiting resistor R2,determine the light output of the LED inthe pickup assembly. Only a minimalamount of LED output is required.

With the LED illuminating the photo-transistor, the potential between Q1 pins3 and 4 is typically about one volt.Comparator IC1 is wired so that its out-put is high when the light path insideOC1 is blocked, and goes low when themotion of the magnetic needle moves toallow an uninterrupted light path. SinceIC1 is powered by a 5-volt supply, itsoutput is TTL compatible. If desired,the output from IC1 can be used topower a relay (K1). Because the volt-age comparator used is limited to a 20mA output, the coil resistance of therelay must be at least 250 ohms.

If desired, the compass needle can bemounted vertically so that it dips up anddown in the presence of a magneticanomaly or disturbance.

Geotech Page 3

Pop

ular

Ele

ctro

nics

, May

197

8 --

Cop

yrig

ht

Ger

nsba

ck P

ublis

hing

, rep

rodu

ce f

or p

erso

nal u

se o

nly

CRT Detector. The inertia-less cathode-ray tube

instrument shown in Fig. 4 is anextremely sensitive, high-speed magne-tometer. Professional CRTmagnetometers can measure extremelyweak magnetic fields. The sensitivity ofthese CRT detectors exceeds that ofboth nuclear and rubidium-vapor mag-netometers by a factor of two to four.However, commercial CRT systems arevery expensive. This forces the experi-menter to fashion a home-brew CRTmagnetometer such as that shown inFig. 4. The display speed of this systemis contingent only on the signal transfertime of the electronics package.

The CRT can be obtained from anoscilloscope or similar instrument. Itshould be an electrostatic -- not electro-magnetic -- system. Because the CRTmust be operated 30’ (9.lm) or morefrom its parent housing, lengthy cablesare required to deliver the filament, cen-tering, focus, and high voltages.

Attached to the glass faceplate of theCRT is light-dependent resistor LDR1and an opaque mask with a tiny aper-ture cut in it. The size of the apertureshould be about the same diameter asthe focused spot on the CRT screen.The photocell/aperture mask assemblyshould be secured to the center of theCRT’s faceplate in an opaque retainercup. Do not use a permanent cementwhen attaching this assembly to theCRT because it may have to be movedsomewhat if a phosphor burn (darkspot) develops on the screen.

The CRT must be operated withoutany type of shielding and should be sup-ported by a nonmagnetic structure. Usewell-insulated cables for the variousCRT operating potentials. Set thebrightness to produce a relatively lowintensity spot, and then focus the spot.Using the horizontal and vertical center-ing controls, position the spot directly inthe hole in the aperture mask. You cantell when the spot is properly posi-tioned with the aid of an ohmmeter.Connect the meter across the leads ofthe photocell and operate the centeringcontrols. The photocell’s resistance willbe very low when the spot is properlypositioned.

When LDR1 is illuminated, the cir-cuit in Fig. 4B causes K1 to close,applying power to READY lamp I1. Iffor any reason the CRT’s beam movesaway from the small aperture, K1 willmomentarily de-energize and extin-guish I1. This triggers an alarm circuit

Geotech Page 4

Pop

ular

Ele

ctro

nics

, May

197

8 --

Cop

yrig

ht

Ger

nsba

ck P

ublis

hing

, rep

rodu

ce f

or p

erso

nal u

se o

nly

composed of SCR1(whose gate is protectedby D3) and audible alarmAl. Even if the beamreturns to the aperture inthe mask, the alarm willcontinue to sound untilRESET switch S1 ismomentarily depressed tointerrupt the dc paththrough SCR1. Diode D2protects transistor Q3from voltage transientsgenerated by K1 duringswitching.

Excursions of theCRT’s electron beam caneasily be calibrated interms of gauss by using asmall calibrating perma-nent magnet of knownfield strength and asquare-ruled paper inter-face or plastic grid on theCRT’s screen.

With the beam inten-sity set low and the spot’sfocus adjusted, R1 can beused to control the sys-tem’s sensitivity. TheCRT sensor can be givensome directionality byhousing it in a steel con-tainer whose sky-facingside has been removed. Ifthe CRT is mounted out-doors, use a nonmagneticweather cover to protectthe CRT and high-volt-age cables from theelements.

As is the case with pro-ton-precession and field-induction magnetometers,the inertia-less CRTinstrument is a total-fieldmagnetometer, rather thanan incremental fielddevice.

Ground-Loop Sensing System.

The chopper-interro-gated ground-loopapproach shown in Fig. 5can be used to augment amagnetometer setup. Theinductor, typically con-sisting of two turns ofinsulated copper wiremeasuring from 2’ to 200’(0.6 to 61 m) in diameter,employs a 330-Hz chop-

per in which Q1 and Q2operate as an astablemultivibrator.

The chopper converts dcor low-frequency ac sig-nals induced across theloop by an airborne mag-netic agent into a serratedac signal train. The traincan then be processed byconventional audio sys-tems. The nulling circuitconsisting of R1, R2, R3,and nulling potentiometerR4 sets the quiescent stateof the detector. Anoptional alarm circuit,shown in the dotted box,can be connected to theoutput of the audio ampli-fier. Diode D2 providesthe rectification requiredby the gate of SCR1. Themagnitude of this gate sig-nal is determined by thevalue of Rd.

Diode D1 “despikes”chopper coil K1, and C4maintains the frequencystability of the multivibra-tor. The circuit should behoused in a small, earth-grounded metal enclosure.The loop can be wound

Geotech Page 5

Pop

ular

Ele

ctro

nics

, May

197

8 --

Cop

yrig

ht

Ger

nsba

ck P

ublis

hing

, rep

rodu

ce f

or p

erso

nal u

se o

nly

around suitably spaced wooden pegsand connected to the circuit via shieldedcable. If the loop is installed indoors, itshould be mounted against a ceiling.Alternatively, it can be mounted on theroofEddy-Disk Magnetometer. Accord-ing to some sources, one presentlyunexplained phenomenon influences thebehavior of eddy-disk devices like thosein automotive speedometers and domes-tic power meters. It has been claimedthat electrically disabled speedometers

have indicated high road speeds whilethe vehicle was stationary. Similarly,there have been reports that homepower meters exhibit sudden bursts ofhigh speed without any increase inenergy consumption.

Shown in Fig. 6 is an instrument thatcan detect anomalous eddy currents.The heart of the device, shown in A, isan aluminum disk that rotates above aniron-core coil containing 15 turns of 3/32” (2.38-mm) wire connected to a pairof receptor stubs formed from 0.25”

(6.35-mm) diameter copper tubing. Asmall, thin iron flag that opposes a rela-tively weak permanent magnet providesa force sufficient to prevent the diskfrom rotating under unenergized condi-tions. The overall design resembles thatof a standard home power meter. Thepermanent magnet used for the brakeshould be positioned near the flag sothat the disk is stationary under ambi-ent conditions.

The motion of the disk is detected byoptical means (see Fig. 6A). Exciter

lamp I1 generates a luminous outputwhich passes through a small aperturein the disk. Light passing through theaperture falls on LDR1 on the other sideof the disk. The light path should beconfined to the aperture in the disk. Asmall opaque tube can be used on eitherside of the disk to confine the light.These tubes will keep the light emittedby I1 from spilling over the edge of thedisk and possibly biasing LDR1. Thetubes should not contact the disksurface.

Geotech Page 6

Pop

ular

Ele

ctro

nics

, May

197

8 --

Cop

yrig

ht

Ger

nsba

ck P

ublis

hing

, rep

rodu

ce f

or p

erso

nal u

se o

nly

As shown in Fig. 6B, LDR1triggers monostable multivibra-tor IC1A which clocks flip-flopIC1B on and off as the diskrotates. Two outputs are pro-vided. One, at the emitter of Q1,can be changed in level to pro-duce a TTL-compatible outputfor driving conventional decadecounters. The other output is viarelay K1, which can be used toactivate a mechanical counter oran alarm.

Potentiometer R2 allows theexperimenter to adjust the sensi-tivity of the sensing circuitry.Because of Q1’s limited current-handling ability, the coil resis-tance of K1 must be at least 250ohms. Control R1 provides ameans for adjusting the intensityof L1.

To keep out any extraneouslight, a nonmagnetic, opaquecover can be mounted over thedisk, L1, and the I1/ LDR1assembly. A larger nonmagnetic(glass or plastic) dome is recom-mended to safeguard the packageagainst moisture and air cur-rents. The receptor stubs can bemounted outside the package.

In Closing. The various home magnetome-

ters that have been presented inthis article should be operated asfar away as possible from anycontaminating magnetic fieldsproduced by electrical machines,permanent magnets, etc. Theyshould also be housed in non-magnetic structures. Armed withthese detectors and scientificcuriosity, you will be wellequipped to investigate mag-netic phenomena-whether theyare produced by natural, man-made, or perhaps even extra-ter-restrial causes.