317 lines
14 KiB
Plaintext
317 lines
14 KiB
Plaintext
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12/19/91 11:14pm
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Basic Eavesdropping #1
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The Electronic Ear
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------------------
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Written By The Freddy
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In Association With The National Newtwork of Anarchists and Nihilists (NNAN)
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Introduction
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------------
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This text file is the first in a series on the topic of eaves-
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dropping. My trusty Webster's Compact Dictionary defines eavesdropping as
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the art of listening secretly. This can be useful to the young anarchist
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in many ways. Suppose that, as a beginning phreak, you are given the
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undubious assignment of being the lookout. Well, you want to hear the
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guard coming while being as far away as possible. Or you stake out your
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mark's house to find out as much as you can before you get your revenge.
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Well, again, you want to hear as much as possible without making yourself
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known. To find out how to properly accomplish these and many other tasks,
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read on.
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Disclaimer
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----------
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This document was intended for informational purposes ONLY, the author and
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the National Network of Anarchists and Nihilists do not endorse or support
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any illegal action presented here or in any other documents which we
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release. The only motivation for the writing of this document is purely
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for educating the general public. The author and the National Network of
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Anarchists and Nihilists will not be held responsible for any actions by
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the reader of this document.
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Description
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-----------
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The Electronic Ear is alot like those "high tech" Listenaiders
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which boost sound. Think of the possibilities. With the Electronic Ear
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you can hear whispers 500 feet away or a conversation half a block away.
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You can listen in and record for all posterity the conversation on the tape
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of your choise. Of course, it is illegal to listen in on and/or record a
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conversation without the permission of the parties doing the conversing.
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Two versions will be presented. One that uses a parabolic dish (like on
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satellites); the other uses a highly directional shotgun microphone. Both
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use the same easy to build superamplifier circuit.
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Parts List
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Amplifier Circuit
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-----------------
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R1 10 k-ohm resistor
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R2 100 ohm resistor
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R3 4.7 M-ohm resistor
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R4,R6 3.3 k-ohm resistor
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R5 220 ohm resistor
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C1 220 pF disc
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C2,C3,C5 0.47 <20>F disc
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C4 1.0 <20>F polarized electrolytic
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IC1 LM387 integrated amplifier IC
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D1 1N34A
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S1 SPST switch
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Mike Electret condenser microphone
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(1) Project box, 2 3/4 by 5 1/8 by 1 3/4
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(1) 1/8 inch microphone input audio jack
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(1) 1/8 inch sound output audio jack
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All resistors are 5 to 10 percent tolerance, 1/4 watt.
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All capacitors are 10 to 20 percent tolerance, rated at 35 volts or more.
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LM387 amp is available in kit form from:
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ALLEGRO ELECTRONICS SYSTEMS
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3E MINE MOUNTAIN
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CORNWALL BRIDGE, CT 06754
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(203)672-0123
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Mail order company. Catalog available.
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Construction Of The Amplifier Circuit
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-------------------------------------
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The Amplifier Circuit is based on an LM387 dual preamp IC. In
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layman's terms, the preamp first increases the amplification from the
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microphone about 47,000 times, and then limits the audio signals of only 1
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volt peak to peak or less to go to the output jack. This will save your
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ears in case one of your less scrupulous friends shoots a cap gun in front
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of the mike. Use a universal solder board for the circuit.
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Construction is pretty straightforward. I have included both the
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schematic and a picture of what the finished circuit should look like.
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Schematic Of The Amplifier Circuit
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----------------------------------
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C6 220pF o To tape Power supply
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----|(--ground | circuit decoupling/filtering
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| C5 \./ or C2
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| .47 <20>F --- headphone ---|(---
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| | amp | .1<EFBFBD>F |
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| ----o----------------o V+ o--o--|(--o--ground
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| | | | C1
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| D1 \/ | | 1000<30>F
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| 1N34A - | |
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| | | | Recorder interface
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|___________o | | J1
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| | | (o)------
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R5 / / R6 | Tip| |
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220 ohm \ \ 3.3 k-ohm |5 \/ |
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/ / /\ ---/\/\/\/---o--ground
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\ \ / \ | R1
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| | / \ o 10 k-ohm
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S1 ----o 6 / IC1b \ 3
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o-o /o--o-------| -------/ LM387 \-------o-ground
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/ | | /--------------------\ |
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| | |7 |8 C4 1.0 <20>F|
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| |------------o |----o---|(---
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| R4 / |
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| 3.3 k-ohm \ |
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| / |
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| \./ C3 |
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| ---.47 <20>F |
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| +| | Headphone amp
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| | | J1
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| ------------------o | (o)-------
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| | 4| | Tip| |
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| / /\ | | |
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| \ R3 / \ | C2 \./ |
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| / 4.7 M-ohm / \ | 4.7<EFBFBD>F --- |
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| \ / IC1a \ | | C1 |
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| | / LM387 \ | | .1<EFBFBD>F |
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| | /-------------------\ | o--|(---o
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| | 2| 1| | Q1 | |
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| --------------o --------- 2N2222 | |
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| | c e | R4 |
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| R2 / V+ o------o----\ /--o-\/\/\-o-ground
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| 100 ohm \ | \/ 1 k-ohm|
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| / R2 / ---- \
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| \ 22 k-ohm\ b| R3 /
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| | / | 27 k-ohm\
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| C2 \./ \ | /
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| .47 <20>F --- C1 --------o-------------
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| R1 | 220 pF \
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|----\/\/\/\-----o----|(------- / R1
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10 k-ohm | | \ 1 k-ohm
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| ---------o---ground /
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Mike o
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Suggested Parts Layout
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----------------------
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Headphnone Mike Jack
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Jack_____ _____
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--| |-----| |------------------------------------------------
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| | | | | -------- |
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ON/OFF | --- --- _____|______|____ |
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switch --- ______________________________________ | | |
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O--| | | __________ | | | |
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--- | -|__________|- _|_ _|_ | | | |
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| | ____/------------\____ | | | | | | | |
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| | \------------/ | | | | | | Battery | |
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| | -|- |_______________| | | | |
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| | Circuit board | | | |
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| -------------------------------------- | | |
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| ----------------- |
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|_______________________________________________________________|
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Notes
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-----
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If you cannot understand the schematic, then get a friend to make
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it for you. You should be able to build the circuit with a minimal amount
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of electrical experiance.
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If you plan to connect the output to the line input of a tape
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recorder, use a 10 k-ohm potentiometer as a level control and be sure to
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use shielded cable to reduce unwanted hiss.
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Test the circuit before building the rest of the Electronic Ear.
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Connect a electret condenser mike to the input jack and a pair of
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headphones to the output. Don't put the headphones directly over your
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ears. I found this out the hard way. Turn the circuit on and listen for
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the squealing sound of the oscillating circuit. If you don't hear it, go
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to the next step. If there is an oscillation problem, increase the value
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of C6 to 330 pF or 470 pF. Also try increasing R5 from 220 ohms to a
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higher value that will reduce or eliminate oscillation, but it will also
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decrease the gain of the circuit. If oscillation is still a problem, then
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try replacing R3 with a 1.5 m-ohm resistor. This should decrease the
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overall gain of the circuit.
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The Parabolic Dish
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------------------
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Parts List
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1 Spun aluminum or plastic parabolic dish
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1 10 inch length of 12 gauge wire
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2 #12 crimp on connector
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Dish available from:
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EDMUND SCIENTIFIC CO
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P.O. BOX 5408
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SCOTTSDALE, AZ 85261
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(609)573-6250
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Mail order company. Catalog available.
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Construction Of The Parabolic Dish
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----------------------------------
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The most effective way of tuning in on distant sounds is to use a
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parabolic dish. I used an 18 inch diameter dish purchased surplus from
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Edmund Scientific. Other dishes, both metal and plastic, will do.
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The microphone must be positioned at the focal point of the dish.
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You could use the complicated algebra method, but an easier way is to
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position the dish in full sunlight and move small piece of paper in and
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out of the center until you see a small, bright spot. Measure the distance
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from the paper to the base of the dish and you have the focal point. If
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the dish is not reflective, try covering it with aluminum foil.
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You want to mount the microphone to a standoff. This can be made
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from a coat hanger adjusted to fine tune the focal point. The microphone
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should be physically insulated from the standoff using double sided tape.
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The finished standoff and mike should look like this:
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_________
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/ \
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Coat | | | Crimp-on spade
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hanger | | | connector (bend
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bent | --|-| out tongue)
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to |
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shape |
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| | Crimp-on spade
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Attach the amplifier to the side of the dish using some hardware or
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double sided tape.
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Paint the dish flat black so it does not glint in the sunlight.
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Also, add a 1/4" 20 bolt and sleeve coupling to one side of the dish to
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provide a meansto secure it to a tripod. This works quite well.
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_
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/
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/ Parabolic
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/ dish
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Amplifier /
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circuit /
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|---/
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| |--\ o\
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|---\
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\
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\
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\
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/\\
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/ \\_
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\ /
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/ \
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/ \ Tripod
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/ /\ \
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The Shotgun Mike
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----------------
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Parts List
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----------
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1 40 inch lenght of 4 inch PVC or ABS plastic pipe
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1 4 inch end cap to fit onto one end of pipe
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1 3 inch round speaker (replaces Mike)
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Construction Of The Shotgun Mike
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--------------------------------
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The Shotgun Mike is cheaper to build than the parabolic dish. It
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does not collect as much sound, though, but it is more directional.
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The speaker needs to be physically isolated from the tube to reduce
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the effects of vibration. I have found that a pice of 2 inch thick foam
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cut to 4 1/2 inches in diameter works well. Punch or cut out a small
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circle in the center so it looks like a doughnut.
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Solder an 8 inch length of shielded cable to the terminals of the
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speaker. Press the magnet of the speaker through the small hole and slip
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the foam and speaker into one end of the tube.
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Solder the other end of the speaker wire to a 1 1/8 inch plug.
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Drill a hole in the end cap for the speaker wire, mount the amplifier, and
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you're set. The finished product should look like this:
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Amplifer PVC pipe
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circuit ---------------------------------------------------
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##########||----| /
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##########|| F | / Speaker
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##########|| o |-|
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##########|| a |-|
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##########|| m | \
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##########||----| \
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--------------------------------------------------
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Conclusion
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----------
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Now that you know how to build an Electronic Ear, you probably want
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to know how to use it. That will be upcoming in a future installment.
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Until then, build one yourself. I can be reached at The DeaTh BoX
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BBS--(714)970-6710--which is the home of NNAN. Well, it's getting late so
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until next time, adieu.
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12/24/91 1:27am
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