# How does the length of the antenna affect wavelength of the wave?

I want to do some calculation of how varying lengths of the antenna will change the wavelength of the wave.

• Do you have a question? Commented Apr 13, 2021 at 22:24
• Antenna design is a topic that fills 600 pages of a \$200 textbook. You'll need to put more effort into this endeavour than you have into this question...
– J...
Commented Apr 14, 2021 at 12:04

The length of the antenna does not affect the wavelength or frequency of the transmitted or received wave. However, an antenna of the correct length for the frequency will be more efficient at transmitting and receiving than an antenna of the wrong length.

The wavelength is set by the frequency of the ocscillator that's driving the antenna.

The standard equation for a wave is v = fλ, where v is velocity, f is frequency and λ is wavelength.

For an electromagnetic wave, we know that v is actually the speed of light, c. So we can rearrange the equation to λ = c/f. The wavelength of the antenna doesn't come in to it.

However, if you select the wrong length antenna, the transmission from it may be a lot weaker than it should be. So the length of the antenna is usually defined by the wavelength, rather than the other way round.

The antenna itself does not change the wave, it just couples it into space, sometimes better and sometimes worse.

The question is how easy it is to get power into or out of an antenna of a particular length. If the antenna is too short, it is like a capacitor to the electricity, and the antenna does not radiate or receive very well. If it is too long, it looks like an inductor, and again it does not work very well. At the optimum length, the antenna actually efficiently transfers power to and from waves in space.

Too long or too short, the transmitted electric waves don’t leave the antenna vicinity, making the power that flows in to the antenna come out again at a different part of the wave, so there is no power that flows out.