Question

Which of the following generates the same field pattern as a vertical dipole antenna?

(a) Yagi antenna

(b) Helix antenna

(c) Alford loop

(d) Microstrip antenna

This question was addressed to me in a job interview.

Question is taken from Point Source Radio Systems topic in section Terrestrial Radio Navigation System of Avionics

Answer 1

Right option is (c) Alford loop

Explanation: Each radiator in the ground station transmitter is an Alford loop. The Alford loop generates a horizontal polarized signal having the same field pattern as a vertical dipole.