History 5 Lesson 150 

Crystal Oscillator

Series of incremental discoveries. Curies discovered piezoelectricity. Used it to build instruments for detecting radioactivity. Piezoelectricity drew Scientific and invented the first oscillator in 1917. Dr.Cady invented his own in 1920. Patent lawsuits ensued.Solid materials can produce electricity when squeezed. Also works in reverse. Crystals can generate oscillating signals with low power. Multiply and divide with low power. Multiply and divide the output frequencies. Important as filters in transmitters and receivers. Better radios appeared in the 1920s. It was used in most radio stations by 1926. Made their way into clocks. Us Army converted its radio equipment to crystal in 1939. The wristwatch appeared in 1969. Critical in all electronics after the 1960s. 

George Washington Carver

George Washington Carver was born in the 1860s. Became a Christian as a boy, learned to give back to others. Earning a college education, he went to work for Booker T. Washington. He ran experimental farms. Mostly known for his farming techniques. Pioneered crop rotation in the South. Promoted peanut recipes Mobile classroom for teaching farmers. Became famous for work with peanuts. Teddy Roosevelt became an admirer, he was honored by the Royal Society of Arts in England. Became nationally known after speaking before congress in 1929. 

Yagi Uda Antenna 

Tohoku university in Japan. Hidetsugu Yagi, researched radio waves. Shintaro Uda studied under Yagi. He invented the Yagi Uda antenna in 1926. Radio waves induce currents in antennas. Yagi Uda increases directivity. It is  a modified dipole, the reflector and directors focus. It was cheap to make. IT was published in an English article in 1928. It was used when broadcasting went mainstream after the war. Yagi Uda antenna works well in VHF and UHF Frequency bands. 


Alexander Fleming was born in Scotland in 1881. Studied under a vaccine professor. He saw hundreds of wounded soldiers die during WWI. Studied bacteria for the next 14 years. Invented Penicillin in 1929. Penicillin can be swallowed or injected. It’s a fungus that kills bacteria. It’s grown in large tanks. 13 years would pass until the first patient was saved. Hard to grow an excited body quickly. Dr. Florey looked up the project in 1938. He worked with Ameraicans to mass produce it.            

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