Question

Which of the following is true regarding the axial mode of radiation in helical antenna?

(a) Radiation is broad, directional along axis and produces minor lobes

(b) Radiation pattern is narrow and no minor lobes are produced

(c) Minor lobes are produced only along the direction of helical axis

(d) The dimensions of antenna are smaller than the wavelength

This question was addressed to me during an interview for a job.

Origin of the question is Frequency Independent Antenna topic in portion Frequency Independent Antenna of Antennas

Answer 1

The correct choice is (a) Radiation is broad, directional along axis and produces minor lobes

For explanation: In Axial mode of radiation, the radiation is in end-fire direction along the helical axis. The radiation pattern of the antenna is broad, directional along axis and produces minor lobes at oblique angles. The dimensions of antenna are approximately in the order of the wavelengths.