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Engineering
Electrical Engineering
Does Heinrich Hertz' apparatus include a proper antenna?
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[QUOTE="tech99, post: 6522012, member: 477979"] The high voltage is generated by an induction coil, which is a step-up transformer. The primary is interrupted by a trembler and a Leyden Jar capacitor is connected across the contact to speed up the collapse of the magnetic field and so increase the secondary voltage. The oscillation does not take place in the induction coil but in the spark-antenna circuit. As the secondary voltage rises up, over maybe a millisecond, it slowly charges the antenna circuit to a high voltage. The spark gap is across the antenna, and when it reaches a critical voltage it breaks down, and a spark occurs. The resistance of the gap then falls to about 1 Ohm, so it discharges the antenna voltage and allows damped oscillation in the series tuned antenna circuit. The breakdown of the spark gap takes only picoseconds, so microwave generation is possible. One of the pioneers, Chandra Bose, experimented with 60 GHz waves generated from a spark gap. With the ships' Morse system, a crystal set would respond to the many sparks per second being produced. Marconi introduced a rapidly rotating interrupter wheel to raise the pitch of the sound. If the ship's detector was a coherer, the receiver had a relay driving a tape printer and a device to tap the coherer after a signal came in, so that arrangement would give a continuous buzz if a signal was present. It is also possible to use a coherer with earphones, in which case it operates like a pair of back-to-back diodes. In such a case ther current must be restricted using a resistor to prevent to coherer "cohering", so to speak. Unfortunately for Hughes, the Royal Society visited his laboratory and Sir William Crookes concluded that the effects were induction. I am not certain myself that Maxwell specifically described how an EM wave might be produced, so Hertz was a real pioneer. [/QUOTE]
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Does Heinrich Hertz' apparatus include a proper antenna?
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