# If the radii of two conductors are r1 (feed arm), r2 (non feed arm) and separated by a distance,then the impedance transformation for a half folded dipole is given by _______

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If the radii of two conductors are r1 (feed arm), r2 (non feed arm) and separated by a distance,then the impedance transformation for a half folded dipole is given by _______

(a) $\left(1+\frac{log⁡(\frac{a}{r1})}{log⁡(\frac{a}{r2})}\right)^2$

(b) $73\left(1+\frac{log⁡(\frac{a}{r1})}{log⁡(\frac{a}{r2})}\right)^2$

(c) $\left(1+\frac{log⁡(\frac{a}{r2})}{log⁡(\frac{a}{r1})}\right)^2$

(d) $73\left(1+\frac{log⁡(\frac{a}{r2})}{log⁡(\frac{a}{r1})}\right)^2$

The above asked question is from Folded Dipole Antenna topic in chapter Folded Dipole & Yagi – Uda Antenna of Antennas

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Correct answer is (b) $73\left(1+\frac{log⁡(\frac{a}{r1})}{log⁡(\frac{a}{r2})}\right)^2$

To elaborate: 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

$Z = Z’\left(1+\frac{log⁡(\frac{a}{r1})}{log⁡(\frac{a}{r2})}\right)^2$

For a half dipole Z’=73Ω

∴ $Z = 73\left(1+\frac{log⁡(\frac{a}{r1})}{log⁡(\frac{a}{r2})}\right)^2$

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