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July Fact-of-the-Day Index

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DateFact of the Day Topic
July 1Hertzian Waves In 1887, Heinrich (Rudolph) Hertz verified James C. Maxwell's 1864 theory that electrical disturbances should propagate through ...
July 2Photoelectric Effect Discovery Heinrich Herz was a Professor of Physics at Karlsruhe and Bonn. In 1887 one his students, Wilhelm Hallwachs ...
July 31880 Optical Telephone Transmission Patent Alexander Graham Bell and Sumner Tainter were granted a U.S. patent in 1880 for a wireless ...
July 4The Edison Effect Thomas Edison created a vacuum-tube diode in 1883, but didn't understand how it worked or appreciate what could be done with it ...
July 5Diode and Triode Vacuum Tube Development University College (London) Professor John Ambrose Fleming was employed by the Marconi Company ...
July 6First Voice Radio Transmission Professor Reginald Aubrey Fessenden was the first person to successfully transmit human voice by radio. The transmission ...
July 7Heterodyne Signal Detection Invention Communication receivers use a Beat Frequency Oscillator (BFO) to make unmodulated continuous wave ...
July 8Superheterodyne Invention The earliest radio receivers consisted merely of RF amplitude-detectors of various kinds connected to antennas. The detectors ...
July 9The First Radio Commercial New York radio station WEAF (which later became WNBC) was the first to transmit a radio commercial ...
July 10Yagi Antenna Invention If asked, many who have studied electronics would tell you Yagi antennas were invented by someone named Yagi ...
July 11Speech Clipping Consonants contain the majority of the intelligence information in speech (the portion that makes it possible to understand ...
July 12Superheterodyne Spurious Responses The intermediate-frequency filter selectivity of a superheterodyne receiver is not a complete indication ...
July 13Speech Articulation and Intelligibility The audio bandpass of communication systems can be limited where the objective is merely to ...
July 14HF Mobile Antenna Efficiency The power radiated by any antenna is equal to the current flowing through its radiation resistance squared, times ...
July 15Radiation Resistance vs. Antenna Resistance The terms 'radiation resistance' and 'antenna resistance' are sometimes used interchangeably by ...
July 16The Term 'Audio' The term 'audio' is widely used by both the general public and engineers, but what exactly does it apply to? Is the sound of your voice ...
July 17Information Theory Information Theory is a branch of statistical communication theory where physical observation information or the information content of ...
July 18Epoxy Resins Epoxy resins are a family of thermosetting resins widely used in potting, casting and encapsulating electrical and electronic components ...
July 19Crosscorrelation Detectors A crosscorrelation detector compares a received signal waveform point-by-point with an internally-generated reference ...
July 20Vacuum Tubes above 100 MHz Several factors degrade the performance of vacuum tubes with increasing frequency. Interelectrode capacitance ...
July 21Parabolic Antenna Feed Illumination An optimal parabolic transmitting antenna converts cylindrical waves radiating from an electromagnetic source ...
July 22Barkhausen Oscillation There is an unusual and little-known way to make triode vacuum tubes oscillate at frequencies far above where they normally ...
July 23Steerable Antenna Vertical Directivity HF dipoles, Yagi's, log-periodic arrays, and other types of antennas are often made horizontally rotatable to ...
July 24Aurora Sputter Fading A particular type of very-rapid and easily-recognizable VHF signal fading was first heard in the 1930's where ...
July 25Meanings of the Term 'Flux' There are many specific applications for the term 'flux' in electronics. One refers to a material that facilitates ...
July 26The Doppler Effect Christian Doppler predicted in 1842 that the frequencies of received waves are dependent upon any motion of a ...
July 27Ferromagnetism Certain materials have a property called ferromagnetism that gives them relative magnetic permeabilities exceeding unity ...
July 28Buffer Amplifiers The term 'buffer amplifier' generally refers to an amplifier whose main function is to provide ...
July 29Does Your Antenna Radiate Particles? There are two correct, but intuitively much different, ways to perceive electromagnetic radiation ...
July 30Vertical HF Antennas Vertical antennas are used far less than horizontal antennas throughout most of the HF spectrum, because ...
July 31Analog TV Transmissions are Partly SSB A variety analog broadcast television transmission standards and sub-standards exist throughout ...

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