Image: Hertz first oscillator

Description: The first spark gap oscillator built by German scientist Heinrich Hertz around 1886, the first radio transmitter, with which Hertz discovered radio waves. It consists of two 1 meter copper wires, supported on wax insulators, with 30 cm zinc balls on the ends. He used different sized balls to change the capacitance, in order to change the frequency. It functioned as a half wave dipole antenna. An induction coil (not shown) applied a high voltage between the two sides, creating sparks across the gap between the small balls at center. The sparks caused oscillating standing waves of radio current in the antenna at its resonant frequency, radiating radio waves in the VHF band. Caption: "The First Oscillator of Hertz. Two copper wires, each 1 metre in length, sup-ported on rods of sealmg wax. The large spheres are of sheet zinc, and are 30 centimetres in diameter. Base 260 x 7.5 centimetres"
Title: Hertz first oscillator
Credit: Retrieved December 30, 2014 from Rollo Appleyard, "Pioneers of Electrical Communication 5: Heinrich Rudolf Hertz" in Electrical Communication magazine, International Standard Electric Corp., New York, Vol. 6, No. 2, October 1927, p. 66, fig. 3 on http://www.americanradiohistory.com
Author: Rollo Appleyard
Permission: This 1927 issue of Electrical Communication magazine would have the copyright renewed in 1955. Online page scans of the Catalog of Copyright Entries, published by the US Copyright Office can be found here. Search of the Renewals for Periodicals for 1954, 1955, and 1956 show no renewal entries for Electrical Communication. Therefore the magazine's copyright was not renewed and it is in the public domain.
Usage Terms: Public domain
License: Public domain
Attribution Required?: No