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 I²R 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?

1. Air
2. Mica
3. Insulating oil
4. Insulating foam

3-26. Which of the following characteristics of a waveguide cause its lower—frequency limitation?

1. I²R 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

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

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