30 4-55.   A unidirectional pattern can be obtained from an end-fire array by using what phase relationship between the energy fed to adjacent elements? 1.       0º 2.     45º 3.     90º 4. 180º 4-56.   Energy is fed to a parasitic element using what method? 1.   Direct coupling 2.   Inductive coupling 3.   Capacitive coupling 4.   Transmission-line coupling 4-57.   The directivity pattern resulting from the action of parasitic elements depends on which of the following element characteristics? 1.   Length of the element 2.   Diameter of the element 3.   Spacing between parasitic and driven elements 4.   Each of the above 4-58.   The advantages of unidirectivity and increased gain can best be obtained by using which of the following elements in a parasitic array? 1.   Driven elements only 2.   Reflector and director elements only 3.   Reflector, director, and driven elements 4.   Driven and director elements only 4-59.   The ratio of energy radiated by an array in the principal direction of radiation to the energy radiated in the opposite direction describes which of the following relationships? 1.   Side-to-side ratio 2.   Front-to-back ratio 3.   Driven-to-parasitic ratio 4.   Reflector-to-director ratio 4-60.   The Yagi antenna is an example of what type of antenna array? 1.   Driven 2.   End-fire 3.   Multielement parasitic 4.   Single-element parasitic 4-61.   The addition of parasitic elements to the Yagi antenna has which of the following effects on antenna characteristics? 1.   Increased gain 2.   Narrower beam width 3.   Narrower frequency response 4.   Each of the above 4-62.   An antenna which is designed especially for vertically-polarized ground waves at low frequencies is the 1.   Yagi antenna 2.   Marconi antenna 3.   Beverage antenna 4.   V antenna 4-63.   What is the phase relationship of the signals that feed the V antenna? 1.       0º 2.     45º 3.     90º 4. 180º 4-64.   A rhombic antenna is essentially a combination of which of the following antennas? 1.   Two stacked long-wire radiators 2.   Two V antennas placed side by side 3.   Two collinear arrays in parallel 4.   Four parallel half-wave radiators 4-65.   A rhombic antenna has which of the following advantages? 1.   Simple construction 2.   Wide frequency range 3.   Noncritical adjustment 4.   Each of the above