# How to determine the best length for a short dipole antenna

If I were to design a dipole antenna that's significantly shorter than usual for the frequency, how can I determine the best length to use? In other words, given a frequency and a maximum length (potentially much less than a quarter wavelength), how should I calculate the best length? Is the answer to simply make it as long as the maximum length allows?

I'm aware that the antenna might not perform well. I'm simply curious about how to find the best solution given those constraints.

Is the answer to simply make it as long as the maximum length allows?

In essence, yes.

Two reasons:

1. $$A_{eff}$$ still depends on physical size; so, you're losing area from which you could be collecting field energy if you make your antenna smaller.
2. The typical example of a short dipole uses loading with a capacitive or inductive element (depending on at what point you place it) to achieve an electrically larger length. That needs to be larger the more missing length you need to compensate. A simple consideration from the same model you use to calculate the size of the necessary load shows that the larger the load, the smaller the bandwidth becomes. You usually prefer antennas that behave well over a larger range to these that are frequency selective in the band of interest.
• nice answer! I think you have a typo at "... a capacitive or reactive element..." and meant "... capacitive or inductive element..." (both of which supply complimentary reactance at the design frequency to achieve "electrically larger length") Feb 2 at 14:49
• I've gone and edited your answer to reflect the above; if it's accepted and not reverted in a couple weeks I'll delete these comments! Feb 2 at 20:03
• @webmarc thanks! Yep! It's weird, but these always mix in my head Feb 2 at 22:06