BoobaJuice: 1930's Radio Engineering

There were many inventions that led to modern radio before and during the 1930s.

In 1904 an inventor named John Ambrose Fleming invented the Fleming valve. This device looked like a lightbulb and was used in radios for amplifying signals. The Fleming tube was replaced in 1907 with the Audison reciever. This was invented by an American named Lee De Forest. The Audison reviever consisted of a vaccum tube to both detect and amplify signals. Forest named his invention after his original design that utilized an audion tube.

Another invention in the early 1900s was the superheterodyne receiver. This was invented by an American named Edwin Armstrong in 1908. This receiver used frequency mixing to convert an incoming signal to a fixed intermediate frequency (IF). The IF's could be processed easier than the older frequency. Older spark gap transmitters made squeals and hums because of the short bursts of waves from morse code signals. The superheterodyne receiver eliminated this. Today most every modern radio uses the superheterodyne principle. In 1933 Armstrong discovered how to broadcast in FM. FM provided a clearer signal.

I remember when we were cleaning my great grandmothers house my Freshman year of high school. My grandfather came across his cigar box radios. One used morse code to turn a lightbulb on and off for a school play and the other was just a regular radio.