Page:Electronics Technician - Volume 7 - Antennas and Wave Propagation - NAVEDTRA 14092.pdf/117

 3-20. Uniform capacitance throughout the length of the line is an advantage of which of the following transmission lines?
 * 1) Coaxial line
 * 2) Twisted pair
 * 3) Shielded pair
 * 4) Two—wire open line

3-21. What is the primary advantage of a rigid coaxial line?
 * 1) Low radiation losses
 * 2) Inexpensive construction
 * 3) Low high—frequency losses
 * 4) Easy maintenance

3-22. The most efficient transfer of electromagnetic energy can be provided by which of the following mediums?
 * 1) Waveguides
 * 2) Twin-lead flat lines
 * 3) Single-conductor lines
 * 4) Coaxial transmission lines

3-23. Copper I$2$R losses are reduced by what physical property of waveguides?
 * 1) Small surface area
 * 2) Large surface area
 * 3) Shape of the waveguides
 * 4) Waveguide material being used

3-24. In a coaxial line, the current—carrying area of the inner conductor is restricted to a small surface layer because of which of the following properties?
 * 1) Skin effect
 * 2) Copper loss
 * 3) Conductor density
 * 4) Waveguide material beingused

3-25. Which of the following dielectrics is used in waveguides?
 * Air
 * 1) Mica
 * 2) Insulating oil
 * 3) Insulating foam

3-26. Which of the following characteristics of a waveguide cause its lower—frequency limitation?
 * 1) I$2$R loss
 * 2) Physical size
 * 3) Wall thickness
 * 4) Dielectric loss

3-27. At very high frequencies, ordinary insulators in a two—wire transmission line display the characteristics of what electrical component?
 * 1) An inductor
 * 2) A resistor
 * 3) A capacitor
 * 4) A transformer

3-28. At high frequencies, which of the following devices works best as an insulator?
 * 1) An open half—wave section
 * 2) An open quarter—wave section
 * 3) A shorted half—wave section
 * 4) A shorted quarter—wave section

3-29. The range of operating frequencies is determined by which of the following waveguide dimensions?
 * 1) The widest (height/width)
 * 2) The narrowest (height/width)
 * 3) The shortest (length)
 * 4) The longest (length)

3-30. The cutoff frequency for a waveguide is controlled by the physical dimensions of the waveguide and is defined as the frequency at which two quarter wavelengths are

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 * 1) shorter than the "a" dimension
 * 2) shorter than the "b" dimension
 * 3) longer than the "a" dimension
 * 4) longer than the "b" dimension