According the this article (which was published somewhere in 2005-2008 I think, but it's still comes up first in Google) the best length for a 72Mhz receiver antenna is 62" (~157.5cm). This puzzles me since in air, the wavelength of a 72Mhz wave is: $$ \lambda_{72}=\frac{c/n_{air}}{72Mhz}=4.16m $$ And $$ \frac{157.5cm}{\lambda_{72}} = 0.38 $$

Which is kinda like a third, so it seem to figure okay, but 50" is about a third as well (same distance), and we see a drop there. Also, 86" is at about half wavelength (~82"), and it doesn't seem to be close to the 62" result.

So, why is it that 62 inch is the right size? Shouldn't half wavelength be a stronger candidate? Ofcourse you can blame it on the experiment, but the guy describes his environment, and he seems to cancel out most of the "noise".

[This might be a better fit under Electrical Engineering, sorry if so]

  • 1
    $\begingroup$ Looks to me like the article in question considers not only the ideal length of a resonant antenna but also the antenna's ability to reject off-band signals (and probably the input impedance the antenna wire is attached to, which matters as well). $\endgroup$ – Carl Witthoft Nov 30 '14 at 13:39

Your Answer

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

Browse other questions tagged or ask your own question.