Question

In which of the following mode, the helical antenna has narrow bandwidth?

(a) Normal mode

(b) Axial mode

(c) Beam mode

(d) End-fire mode

This question was addressed to me by my college director while I was bunking the class.

This key question is from Frequency Independent Antenna topic in chapter Frequency Independent Antenna of Antennas

Answer 1

Correct option is (a) Normal mode

Explanation: The radiation pattern of a helical antenna is a combination of small dipole and loop antenna. In normal mode of radiation, it provides narrow bandwidth and low radiation efficiency. Axial mode is also known as beam mode or end-fire mode.