Question

On which of the following factors does the overall impedance of the unequal conductor folded dipole depends?

(a) Only thickness of conductors

(b) Space between conductors

(c) Radiation resistance of the dipole

(d) Radii, radiation resistance and space between conductors.

The question was asked by my school teacher while I was bunking the class.

Enquiry is from Folded Dipole Antenna in chapter Folded Dipole & Yagi – Uda Antenna of Antennas

Answer 1

Correct choice is (d) Radii, radiation resistance and space between conductors.

For explanation I would say: If the radii of two conductors are r1 (feed arm), r2 (non feed arm) and separated by a distance, then the impedance transformation for folded dipole is given by

\(Z = Z’\left(1+\frac{log⁡(\frac{a}{r1})}{log⁡(\frac{a}{r2})}\right)^2\) and Z’ is the radiation resistance of the dipole used (which depends on the length of the dipole).

So the overall impedance depends on radii, radiation resistance of the dipole and space between conductors.