1-22-12

Exercise LA12-31
Questions Based on LA12-30 Supplement 1, Pages 1 - 28
20 points

ELT 135/OEET  210

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Electromagnetic Radiation
p. 7
  1. Is light a form of electromagnetic (EM) radiation? Yes or No
  2. Are X-rays a form of EM radiation? Yes or No
  3. Who first postulated (predicted the existence of) electromagnetic waves? __________________

p. 11 bottom
  1. In a vacuum, does EM radiation travel at the speed of light (relative to the observer)? Yes or No
pp. 13 - 14
  1. Are sound waves EM radiation? Yes or No
  2. What wavelengths of EM radiation can the human eye see? ______________________
  3. Are radio waves ionizing radiation? Yes or No

Electronic Oscillators
Oscillators are used to produce the radio-frequency alternating current used in radio communications. (Radio-frequency is a term used to denote frequencies that are high enough to be used for communication by electromagnetic radiation. TV signals and microwave beams are examples of radio-frequency alternating current.)
pp. 17 - 18
  1. What two types of repetitive electronic signals are often produced by oscillators? ______________________
  2. What type of output waveform is produced by harmonic oscillators? ___________________
  3. Which has better frequency stability, crystal oscillators or LC oscillators?
  4. What type of output waveform is produced by relaxation oscillators? _______________

Radio Control
We're going to be studying radio control as one application of alternating current. With increased use of civilian and military remotely-piloted vehicles, this is an appropriate subject for today. (An example of civilian remotely-piloted vehicles are remote-control planes and helicopters used by realtors to take arial photos of houses.)
p. 25
  1. When did Nikola Tesla demonstrate a remote-control boat? ___________

p. 26
  1. Interference from which radio band is better rejected by crystal oscillator superheterodyne receivers (as opposed to earlier receivers)? _______________

p. 27
  1. What does PWM stand for? __________________________
  2. What does PPM stand for? ___________________________
  3. Which type of modulation is most commonly used today for radio control? ________________________
  4. Which type of modulation has the advantage of bit-error checking? _____________________



 
 
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