Page:Electronics Technician - Volume 7 - Antennas and Wave Propagation - NAVEDTRA 14092.pdf/119

3-42. How is the cutoff wavelength for a circular waveguide computed?

1. 1.17 times the radius of the waveguide
2. 1.17 times the diameter of the waveguide
3. 1.71 times the diameter of the waveguide
4. 1.71 times the radius of the waveguide

3-43. The field configuration in waveguides is divided into what two categories?

1. Half-sine and dominant
2. Transverse electric and transverse magnetic
3. Transverse electric and dominant
4. Transverse magnetic and half-sine

3-44. With a mode description of TE_1,0, what maximum number of half-wave patterns exist across the "a" dimension of a waveguide?

1. One
2. Two
3. Three
4. Four

3-45. With the mode description, TE_1,0 what maximum number of half-wave patterns exist across the diameter of a circular waveguide?

1. One
2. Two
3. Three
4. Four

3-46. Which of the following devices CANNOT be used to inject or remove energy from a waveguide?

1. A slot
2. A loop
3. A probe
4. A horn

3-47. Loose coupling is a method used to reduce the amount of energy being transferred from a waveguide. How is loose coupling achieved when using a probe?

1. By doubling the size of the probe
2. By increasing the length of the probe
3. By decreasing the length of the probe
4. By placing the probe directly in the center of the energy field

3-48. Increasing the size of the loop wire increases which of the following loop capabilities?

1. Efficiency
2. Bandwidth coverage
3. Power-handling capability
4. Each of the above

3-49. A waveguide that is not perfectly impedance matched to its load is not efficient. Which of the following conditions in a waveguide causes this inefficiency?

1. Sine waves
2. Dominant waves
3. Standing waves
4. Transverse waves

A waveguide iris that covers part of both the electric and magnetic planes acts as what type of equivalent circuit at the resonant frequency?

1. As an inductive reactance
2. As a shunt resistance
3. As a capacitive reactance
4. As a shorted 1/4 wave stub

3-51. A horn can be used as a waveguide termination device because it provides which of the following electrical functions?

1. A reflective load
2. An absorptive load
3. An abrupt change in impedance
4. A gradual change in impedance

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