CURRENT VERSION MOVED TO http://amasci.com/freenrg/ufoscope.html UFO SCOPE (c)1996 William Beaty Needed: - Binoculars - Small solar cell - Audio amplifier - Headphones Something I always wondered about regarding UFO sightings. Say its night, and you see a light in the distant sky. Is it really an airplane? Or suppose it's behaving oddly, performing manouvers impossible for an aircraft, etc. Is the light coming from that object similar to that of an ordinary 120V AC lightbulb? Specifically, is the light amplitude of that object pure and smooth DC? After all, nearly all manmade light sources are modulated as a result of their AC power supplies, so their brightness is vibrating with audio frequency. Connect a solar cell to an audio amplifier, hold it under an incandescent bulb, and you'll hear MMMMMMMMMM at 120Hz. Therefor we should ask: what sort of vibration might be imposed on those distant and mysterious lights in the sky, hmm? As a kid with an electronics hobby I once taped a selenium solar cell to the eyepiece of a small 50X telescope, routed it to an audio amplifier, then pointed it at distant light sources at night while listening to the signal. Incandescent streetlights give a deep hum, their AC light output is a pure 120hz sine wave. Mercury and sodium vapor bulbs are nonlinear, they give a complex 120hz waveform that sounds like WHAANNNNNNNNN. Neon signs sound different, with a squealy high frequency buzz component to their 120hz fundamental. Automobile headlights are DC, so I never tried viewing them. Recently I saw an article by (I think) Don Lancaster which mentioned that headlights are modulated by car vibrations, so I checked it out and yes, car headlights give off a continuous soft gonging sound even on smooth highways. Their filaments vibrate, and different cars give different pitches of "bell" sounds. Aircraft strobes are easy to detect as a loud clicking. Other aircraft lights *may* have a standard 800Hz modulation (from their 400Hz supplies), but it wasn't loud enough to hear from distant aircraft lights. Perhaps the thermal inertia of their filaments tends to filter out any high frequencies, whereas 60Hz is slow enough to be "broadcast" by light bulb filaments. Maybe with a low noise detector and some bandpass filtering, the 800Hz of aircraft lights could be sensed. I put together a better viewer recently. Binoculars provide a "sighting scope," even when one eyepiece is occupied by a photocell. A Seimens BPW34 P.I.N. photodiode and a low-noise opamp front end gives a bit more gain than my selenium cell. Headphones give much better low frequency response than a speaker. And the whole thing can be battery powered and duct-taped to a set of large-aperature nighttime binoculars. Any light source seen by your eye through one side of the binocs will be heard as optically demodulated audio picked up by the other side. ------------------------------------------------------------------------- 220K Use 9V battery as power supply ____/\/\/\______ | | +9V to opamp + pwr (pin 7) BPW34 | |\ | Gnd to opamp - pwr (pin 4) (+)______|/|_____|___|- \ | |\| | \______|____(out) __|+ / TL071 | |/ probably needs a capacitor in (+)___/\/\/\___|___/\/\/\_ series with the output (10uF) 47K 47K | | V gnd My "I to V" Photodiode Lo-noise Front End ------------------------------------------------------------------------- The above is a Current to Voltage converter circuit: if a 10 microamp signal comes from the photodiode, then a 2.2v signal will appear at the opamp output pin. The input is DC coupled for good lo-freq response. However, bright lights will overload the circuit. Here's an AC-coupled version: ____/\/\/\______ | | BPW34 .1uF | |\ | (+)____|/|_____.______| |__________|___|- \ | |\| | | | | \______|____ / __|+ / \ | |/ 10K / (+)___/\/\/\___|___/\/\/\_ \ | | | V V gnd gnd I powered mine with a single 9V battery. The output signal will ride on 4.5VDC, so you might need to put a capacitor in series with the output to block the DC (my audio amp already had a capacitor in series with the input.) Either that, or use two 9V batteries as a standard bipolar supply, and ground the (+) input pin of the op amp. If you build this "UFO Scope," definitely make a point to use it quite a bit before going hunting for "craft." You want to become familiar with the sounds of all conventional light sources, including lamps, headlights, aircraft, fires, and if you manage to crank the gain high enough, the twinkle patterns of various stars. That way you'll be able to point the device at the local version of "Marfa Lights" and either say "yeah, sure, it's just headlights," or possibly "holy $#!%!, the aliens modulate their ship-lights for voice communications!" Spa fon! :) To greatly increase the sensitivity (by maybe 100x), replace the BPW34 with a phototransistor. I haven't tried this myself, so I can't recommend any particular phototransistor to try. Find one with a large active area if possible. Another idea: build two sensors, install them in both eyepieces, and send the signals to stereo headphones. Then put an IR filter over one lens, and no filter (or an IR-cut filter) over the other (or perhaps magenta on one, and green on the other). This would be harder to aim, but it would let you hear the colors of the light as stereo information. If the light source was changing colors, this might sound very interesting. At the very least, it would give you more clues for recognizing mundane light sources. Incandescent lights would be loud in the IR earpiece, while merc vapor lights would not. If one of these audio photosensor circuits was attached to the eyepiece of a large telescope, would any interesting sounds be received? For example, the flame of a candle *sounds* like the low rush of a burning candle. If the nucleus of a comet has wailing gas jets, occasional explosions, vibrating plasma, etc., perhaps some of the comet's reflected light will become modulated, and the original sounds in the comet's atmosphere could be extracted by the telescope and photodetector. If the gain could be raised by orders of magnitude, it might become possible to monitor the moon at new phase, and pick up tiny signals of lunar meteor strikes. Their brief flashes would sound like clicks. Star-twinkle, if it contains moving interference fringes, might do more than make rumbles and thumps, it might ping or squeak. Lunar occultation of stars also might create brief audio tones because of interference patterns. And if significant numbers of amateurs start listening to the sky as well as watching it, perhaps unexplainable noises will lead to new discoveries for conventional (non-fringe!) science. So far I've not encountered any mysterious lights. I have found that my single opamp stage doesn't give enough gain to "hear" the dimmest of the light sources without burying them in noise, so it's time to modify the thing. Extra gain stages, bigger initial gain resistor, a few tens of picofarads across the gain resistor to prevent oscillation, maybe a phototransistor replacing the photodiode to give higher front-end gain, and perhaps sacrifice low-freq response by making it AC coupled, so bright lights won't drive the opamp's output to the rails. The Marfa Lights: http://www.urbanlegends.com/science/marfa_lights.html Diode Optical Receiver: http://www.qsl.net/k3pgp/Construction/Frontend/frontend.htm ((((((((((((((((((((( ( ( ( ( (O) ) ) ) ) ))))))))))))))))))))) William J. Beaty SCIENCE HOBBYIST website billbeskimo.com http://amasci.com EE/programmer/sci-exhibits science projects, tesla, weird science Seattle, WA 206-762-3818 freenrg-L taoshum-L vortex-L webhead-L