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228 lines
11 KiB
Plaintext
228 lines
11 KiB
Plaintext
Tesla coil information
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Newsgroups: rec.radio.amateur.misc
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From: regnad@hal.gnu.ai.mit.edu (Paul Prescott)
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Subject: Re: Telsa Coils
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The best single source for information about Nikola Tesla, Tesla coils, and
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similar apparatus is:
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Lindsay Publications, Inc.
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P.O. Box 12
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Bradley, IL 60915-0012
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Lindsay's offers primarily reprints of books and other information concerning
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technology and techniques no longer in general use.
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Recently I noticed the book "Inventions, Researches, and Writings of Nikola
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Tesla" by Thomas Commerford Martin at a local bookstore. Lindsay's offers
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this book, but the one at the store was published by someone else, so this
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book is currently available from two publishers. Note: this book was
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originally published in 1894 and deals mostly with Tesla's work with
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polyphase currents and his lectures and demonstrations up to that time.
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There is some information on his early work with "Tesla coils", but he was
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actually just beginning his more famous work in this area at the time.
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(Tesla's Colorado Springs experiments took place in 1899-1900.)
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Regarding the specific questions on Tesla coil construction: There are a
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number of factors that need to be taken into account to get the best
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performance (longest sparks). One of them, the "Q", has already been
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mentioned. Basic rule of thumb is you want the length of the secondary
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coil to be 2 to 2-1/2 times the diameter. The next is a lot more tricky to
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work out. The length of wire used in the secondary should be equal to a
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quarter wavelength of the resonant frequency. This way you have a voltage
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maximum at the free end of the coil. From what I can tell (I've never
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actually built a Tesla coil due to lack of money and facilities to do the
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job right) this is no easy task. You have to figure out where the secondary
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is self-resonant, and tune the primary accordingly. Alternately, or in
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combination, you can tune the secondary by means of what Tesla called an
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"elevated capacity", those globular capacitors one often sees on the end
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of Tesla coil secondaries. The disadvantage of the elevated capacity is
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that it accumulates a charge. This should make for shorter, less continuous,
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less impressive discharges as opposed to a point. Also, it's quite a bit
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more dangerous due to the accumulated charge.
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The most common alternative to the single spark gap in the primary, which
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offers improved performance, is the rotary spark gap. This is a set of
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rotating contacts to increase the number of sparks and get more energy
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into the system. I have heard of the vacuum tube driven primary technique
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but I haven't heard of many successes using it. I'm figuring it's more
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difficult because the tube oscillator must be tuned to the frequency of
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the rest of the system, and this is usually not a known quantity until
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after everything has been tuned up and operating.
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I hope this information is of some use, and again I apologize for taking
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up so much space on a (somewhat) unrelated topic. Is there a Tesla
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mailing list, or enough interest to start a newsgroup? :)
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Paul Prescott
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N1AAC
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regnad@gnu.ai.mit.edu
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From: mac@cis.ksu.edu (Myron A. Calhoun)
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Newsgroups: rec.radio.amateur.misc
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Subject: Here is a TV flyback Tesla design
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While cleaning up my workroom I found a schematic for a "TESLA COIL KIT"
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sold (many years ago) by B & F Enterprises, 119 Foster Street, Peabody,
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Massachusetts 01960 (617) 531-5774:
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O CAP terminal (VERY HIGH VOLTAGE!)
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+--------------------------------+ |
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| +------------+ | |
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| | / | | |
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| |/ | | || $ ******** DANGER *******
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+--------| | L2 = $ || $ * *
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2N3055 |\ L1 = 4 $ 10 $ || $ L3 * I TAKE ABSOLUTELY *
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| v turns $ turns$ || $ is a * *
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| $ $ || $ fly- * ** NO ** *
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+---+ +--$ +--$ || $ back * *
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| | | $ | $ || $ xfrmr * RESPONSIBILITY FOR *
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| ^ | | $ | $ || $ * YOUR USE OR ABUSE *
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2N3055 |/ | | $ | $ || $ * OF THIS CIRCUIT!!! *
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+--------| | | | | $ || $ * *
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| |\ | | | | | || $ ******** DANGER *******
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| | \ | | | | | |
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| +--|------|--+ | | +------o 1 8 - 5 Pin connections
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+--------------|------|-------|--+ +-----o 8 7 5 4 to the following
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| | | +----o 5 6 6 2 flyback
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| | | +---o 7 4 8 1 transformers:
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| | | | | | | +-- 738192
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+------|-------|-----------| | | +----- 32-10008-4
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|27 ohm|240 ohm| | | +-------- 32-10014-1
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+--R1--+---R2--+ | +----------- 32-8859
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| | -----
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- 12 volts +
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Quoting from the instructions:
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"WE TAKE NO RESPONSIBILITY FOR YOUR ACTIONS!!!
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The new windings must be added to the flyback transformer to allow
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adequate transistor drive capability. These windings are hand wound
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on the bottom leg of the ferrite core where the original filament
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winding was located. Remove and discard the original filament winding.
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In its place, wind first a ten turn, center-tapped, winding using
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approximately 30 inches of #20 or larger hookup wire. This is easily
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accomplished by winding five turns at one end of the core and then
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twisting a loop in the free end before adding the second five turns.
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The complete ten-turn winding should then be held in place with a turn
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or two of electrical tape with the two ends and the center loop all
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protruding. Connection can be made to the center loop when the
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insulation has been carefully removed. If it becomes necessary to cut
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the center loop, be sure that the two ends are scraped and joined to
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form a mechanical as well as an electrical center-tap to the winding.
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[L2 in my drawing]
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"The second winding should be wound directly on top of the first but
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it should only have a total of four turns--two each side of the
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center-tap. Again, wind two turns of #20 or larger hookup wire, pull
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and twist a center loop, and wind the other two turns. Tape this
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winding in place on top of the first. Do not let the center taps of
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two windings touch each other but they should not be more than one
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quarter of an inch apart. [L1 in my drawing]
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"Wire the modified transformer to the transistors and the bias circuit
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resistors as indicated on the schematic circuit diagram. Be sure to
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mount the transistors on a suitable heat sink with the insulating
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hardware provided to protect them from over heating. Since the
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collector connection of these transistors is made to the case, it is
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necessary to keep them electrically isolated from one another and
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from the heat sink and insulators are provided to allow this. Heat
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sink area of approximately 25 square inches should be adequate. If,
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however, the power transistors become too hot to hold a finger on,
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more heat sink area should be provided. Heat sink material of one-
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eighth inch aluminum is desirable.
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"Note: If Oscillation does not start Immediately Interchange the two
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Transistor Base connections [capitalization as in original!]
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"CAUTION: LETHAL VOLTAGES ARE INHERENT IN THIS DEVICE. EXTREME
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CAUTION MUST BE EXERCISED TO KEEP THE FULL OUTPUT OF THIS DEVICE
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FROM BEING APPLIED LIMB-TO-LIMB OF ANY LIVING ANIMAL. SEVERE BURNS
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OR DEATH MAY RESULT FROM CONTACT WITH THE FULL OUTPUT..."
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There were other instructions about how much damage might accrue to a
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human if contact were made to the high-voltage output, so BE CAREFUL!
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I used one-half watt resistors for R1 (27 ohms) and R2 (240 ohms) and
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got a nice Jacob's ladder effect. It also wiped out most of the
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computer terminals in the entire building, so I couldn't run it very
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much! I later tried 18 volts and one resistor zapped immediately!
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Date: Tue, 27 Sep 1994 18:00:34 EDT
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From: MR GEORGE R BELL <JBGP26A@prodigy.com>
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To: mtracy@arrl.org
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Subject: Error in TESLA.TXT file and more Information
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-----------------------------------------------------------------------
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There is an error in the schematic diagram for the transistorized Tesla
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coil. In the configuration shown, the positive supply voltage goes
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through L2 to the Bases of Q1 and Q2, with the emitter grounded. This
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would tend to draw a very heavy current from the power supply, only
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limited by the resistance in L2 and the Base-Emitter junction in the
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transistors.
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R1 and R2 are the base biasing resistors. The connection between these
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two resistors is shown going through L1 to the collectors of the
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transistors.
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For proper operation of this circuit, the respective ends of L2 should
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be connected to the Collectors of the transistors, and the ends of L2
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should be connected to the bases. This will allow proper biasing and
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oscillation of the circuit.
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Also, for the modern builder of Tesla Coils, the following are three
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books I feel are essential reading:
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1) "Modern Tesla Coil Theory" by Duane A. Bylund, Tesla Book Company,
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P. O. Box 121873 Chula Vista CA 91912. This is the best modern book I
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have read on the subject of Tesla Coil Building and Theory. Covered
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are aspects Capacitive Discharge, Vacuum Tube, and Transistor Tesla
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Coils as well as basic theory. It cost about 25 dollars two years ago
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and is 140 pages, 8 and a half by 11 format. I recommend any potential
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builder obtain this book!
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2) "The Tesla Coil Compendium" by Randall S. Peterson, 16671 T. R. 51,
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Mt. Cory OH 45868. Phone 419-358-1222. A complete description of
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several successful Tesla Coil projects. Very Good Info. Approx. 20
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dollars 2 years ago. About 100 pages. May be available at the Tesla
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Book Company See 1 above)
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3) "Tesla Handbook", by J. H. Couture, JHC Engineering, 10823 New
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Salem Point, San Diego, CA, 92126. Very Good Information with a
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systematic step-by-step method for construction of Tesla Coils of all
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sizes. Approx. 20 dollars two years ago. May be available at the
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Tesla Book Company See 1 above)
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I hope the above information is helpful. 73 de WB4GHZ, --- George
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From: <deap1032@servus.rus.uni-stuttgart.de>
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Subject: Tesla.txt
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To: mtracy@arrl.org
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Date: Thu, 13 Oct 1994 19:13:22 +0100 (MEZ)
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------------------------------------------------------------------------------
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Hello,
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As to tesla coils there is a good scientific article:
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"A Tesla transformer high-voltage generator", C.R.J. Hoffmann
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Reviev of Scientific Instrumentation, Vol. 46, 1.Jan. 1975, pp1-4.
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73, Moritz DL5UH
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The members and HQ staff would like to thank the following people for
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their contributions to this information file:
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N1AAC, W0PBV WB4GHZ DL5UH
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Send any additional information or changes to mtracy@arrl.org.
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73 from ARRL HQ.
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