Image: Marconi's first radio transmitter

Description: Recreation of one of the first radio transmitters, built by Guglielmo Marconi in August 1895 during his development of radio communication. It was a spark-gap transmitter which generated radio waves by an electric spark between two electrodes of a Righi spark gap (left, on table). The high voltage to produce the spark was generated by an induction coil (center) powered by a battery (on floor). A telegraph key (right, on table) in the primary circuit allowed the operator to switch the transmitter on and off rapidly, producing pulses of radio waves which spelled out text messages in Morse code. This was the first transmitter which used Marconi's invention of a monopole antenna. Marconi found that by connecting one side of the transmitter to an elevated copper sheet "capacity area" (top) and the other side to ground (earth), he could transmit longer distances than when using the previous dipole antennas invented by Hertz. This crucial innovation reduced the frequency of the radio waves, and radiated vertically polarized waves which had a greater range.
Title: Marconi's first radio transmitter
Credit: Retrieved January 28, 2016 from Guglielmo Marconi, "Looking back over thirty years of radio", Radio Broadcast magazine, Doubleday, Page, and Co., New York, Vol. 10, No. 1, November 1926, p. 31 on http://www.americanradiohistory.com
Author: Guglielmo Marconi
Permission: This 1926 issue of Radio Broadcast magazine would have the copyright renewed in 1954. 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 1953, 1954, and 1955 show no renewal entries for Radio Broadcast. Therefore the copyright was not renewed and it is in the public domain.
Usage Terms: Public domain
License: Public domain
Attribution Required?: No