6 1-45.   A flexible waveguide is used in short sections because of the power-loss disadvantages.  What is the cause of this power loss? 1.   Walls are not smooth 2.   E and H fields are not perpendicular 3.   Cannot be terminated in its characteristics impedance 4.   Wall size cannot be kept consistent 1-46.   The choke joint is used for what purpose in a waveguide? 1.   To reduce standing waves 2.   To restrict the volume of electron flow 3.   To prevent the field from rotating 4.   To provide a temporary joint in a waveguide during maintenance or repair 1-47.   A circular waveguide is normally used in a rotating joint because rotating a rectangular waveguide would cause which of the following unwanted conditions? 1.   Oscillation 2.   Large power loss 3.   Decrease in bandwidth 4.   Field-pattern distortion 1-48.   In your waveguide inspections, you should be alert for which of the following problems? 1.   Corrosion 2.   Damaged surface 3.   Improperly sealed joints 4.   Each of the above 1-49.   What type of corrosion occurs when dissimilar metals are in contact? 1.   Contact corrosion 2.   Metallic corrosion 3.   Electrical corrosion 4.   Electrolytic corrosion 1-50.   Internal arcing in a waveguide is usually a symptom of which of the following conditions? 1.   Change in mode 2.   Electrolysis at a joint 3.   Moisture in the waveguide 4.   Gradual change in frequency 1-51.   What is the primary purpose of a directional coupler? 1.   To sample the energy in a waveguide 2.   To change the phase of the energy in the waveguide 3.   To change the direction of energy travel in the waveguide 4.   To allow energy in the waveguide to travel in one direction only 1-52.   What is the electrical distance between the two holes in a simple directional coupler? 1.   1/8 wavelength 2.   1/4 wavelength 3.   1/2 wavelength 4.   3/4 wavelength 1-53.   When the two portions of a reflected wave reach the pickup probe of an incident-wave directional coupler, what is their phase relationship? 1.     45º out of phase 2.     90º out of phase 3.   120º out of phase 4.   180º out of phase 1-54.   The highest frequency at which a conventional circuit can oscillate is reached when which of the following values can be reduced no further? 1.   Total resistance 2.   Total inductance only 3.   Total capacitance only 4.   The total capacitance and inductance