Chapter 1 Flashcards
Sound travels through air as __________ or rapid fluctuations in air pressure.
pressure waves
Rapid fluctuations in air pressure.
pressure waves
The rates of fluctuation in air pressure that we humans can perceive as sound is commonly said to vary between ____
20 cycles per second and 20,000 cycles per second.
Few adult individuals can hear above
15 to 17 kHz
When sound waves hit a microphone, the pressure fluctuations are converted into fluctuations of ___________ on a wire.
electric voltage
The fluctuations of voltage that represent sound and travel down a wire are known as an ____________
audio signal
__________ are translated back into sounds by speakers and headphones.
Signals
Radio propagates sound signals long distances through air and space by the use of high frequency ________
carrier waves
The sound signal is imposed on the carrier wave by a process called ___________
modulation
The carrier wave then carries the signal the long distance to the _________
radio receiver
FM stands for ____________
Frequency Modulation
In FM radio, the audio signals are imposed upon the carrier waves using ____________
frequency modulation
This means that the instantaneous frequency of the high frequency carrier wave (91,500,000 Hertz - cycles per second) is altered (modulated) by the instantaneous value of the audio signal.
frequency modulation
In AM radio, it is the ________ of the carrier signal that is modulated.
amplitude
In 1864 ____________ showed mathematically (theoretically) that electromagnetic waves could propagate through free space.
James Clerk Maxwell
The discovery of these _____________ (radio waves) prompted many experiments by physicists.
“Hertzian waves”
In 1886 ____________ noticed the same sparking phenomenon and was able to demonstrate the existence of electromagnetic waves in an experiment confirming Maxwell’s theory of electromagnetism.
Heinrich Rudolf Hertz
The father of radio
Guglielmo Marconi
In _____, Guglielmo Marconi began pursuing the idea of building a wireless telegraphy system based on Hertzian waves (radio).
1894
_______ gained a patent on the system in 1896 and developed it into a commercial communication system over the next several years.
Marconi
Early uses were maritime, for sending telegraphic messages using ___________ between ships and land.
Morse code
Radio was _____ to develop.
slow
One of the most memorable uses of early radio was during the sinking of the __________, including communications between operators on the sinking ship and nearby vessels, and communications to shore stations listing the survivors.
Titanic in 1912
___________ accelerated the development of radio for military communications
World War I
_________ was a huge proponent of radio. Communication between ships allowed precise locations to be determined.
The US Military
_____________ held patents and manufactured virtually all parts required for radio broadcast.
British Marconi company
In _____, General Electric developed a new radio technology. Was poised to sell to Marconi comp.
GE president and secretary of Navy came to an “agreement.
1919
________ was formed as a subsidiary of GE
RCA
RCA
formed as a subsidiary of GE
________ brought together the major companies involved in radio research. Pooled patents & coordinated research
RCA
