The far-zone power density radiated by a helical antenna is approximated as:\({{\rm{\vec W}}_{{\rm{rad}}}} = {{\rm{\vec W}}_{{\rm{average}}}} \approx \widehat {{{\rm{a}}_{\rm{r}}}}{{\rm{C}}_0}\frac{1}{{{{\rm{r}}^2}}}{\cos ^4}{\rm{\theta }}\)The radiated power density is symmetrical with respect to φ and exists only in the upperhemisphere: 0 ≤

• A. 1.5C0,10dB
• B. 1.256C0,10dB
• C. 1.256C0,12dB
• D. 1.5C0,12dB