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 ?

  • $\begingroup$ One of them is wrong by an exponent in $\lambda$. Otherwise, with applying the basic calculus rules for division and roots, they are identical. $\endgroup$ Sep 18 '20 at 20:13
  • $\begingroup$ Hello Abdullah, and welcome to this site! :-) $\endgroup$
    – Mike Waters
    Sep 18 '20 at 21:28
  • 1
    $\begingroup$ The Gain is extremely sensitive to the error in winding geometry from an ideal helical shape thus the latter equation from Kraus leads to higher gain than best effort by a few dB using $$HPBW = k \lambda ^{\dfrac{3}{2}}$$ $\endgroup$ Sep 19 '20 at 15:26
  • 1
    $\begingroup$ Hello Abdullah, I replaced your equations in .png files with MathJax equations. Here's a quick introduction to MathJax. $\endgroup$
    – rclocher3
    Sep 29 '20 at 16:21

Kraus says

$${52}\over{{C\over\lambda} \sqrt{n{S\over\lambda}}} $$

Which is your second equation.

Be aware that this only holds for a narrow range of diameters and spacings: $0.8<{C\over{\lambda}} <1.8$ ; $12<\alpha<14$ and $n\ge4$


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.