can someone tell me what are the formulas of HPBW for a helical antenna?
I've searched a lot and I saw that there are two different formulas of HPBW for the helical antenna,
this one,
$$ \mathbf{(HPBW)} = [\frac{52}{C} \sqrt{\frac{\lambda^2}{NS}}] $$
and this one,
$$ \mathrm{HPBW} \simeq \frac{52}{\frac C\lambda \sqrt\frac{NS}{\lambda}} \mathrm{degrees} $$
so what is the difference between both ?