Fractal Antennas more efficient?

Mike Hicks writes "Scientific American has a short article talking about fractal antennas. They can be 25% more efficient when used in place of the stubby antennas on cellular phones. An antenna that's fun to look at -- who'd a thunk it? "

Comments

25% more efficient? That is meaningless by itself

[glitch!]

An antenna radiates some (or most) of its energy, and sends the rest back toward the radio. This ratio is what we call SWR. Of the returned energy, some might be lost in the feedline. The rest reaches the radio and bouces back to the antenna for "another try".

If we have feedlines that are relatively long for the frequency, we get concerned about the SWR so that our energy is not wasted heating up the coax between the radio and the antenna. If our feedline is short, then the SWR is a factor if it raises the voltage high enough that the reflected energy bothers the radio. That can be really exciting if you are looking at hundreds of watts, but should not be a factor with the low power levels we are contemplating here.

So if our feedline is short enough, as is common with handheld radios (and cellular phones are radios, of course), our antenna is going to be radiating nearly 100% of the power. It is like the "efficiency" of an electric heater - an electric heater is ALWAYS 100% efficient.

Perhaps the authors really mean that their antennas can direct the radio energy in a more useful direction, such as horizontally. Often this is exactly what we want, and we already have antennas made just for this (such as a vertical dipole). If this is what they are getting at, I did not see this in their report.