About Gain Plots

The true measure of the effectiveness of an antenna in any given applica-

tion is determined by the gain and radiation pattern measurement. For

antennas gain is typically measured relative to a perfect (isotropic) radia-

tor having the same source power as the antenna under test, the units of

gain in this case will be decibels isotropic (dBi). The radiation pattern is a

graphical representation of signal strength measured at fixed distance from

the antenna.

Gain when applied to antennas is a measure of how the antenna radiates

and focuses the energy received into free space. Much like a flashlight

focuses light from a bulb into a specific direction, antennas can focus RF

energy into specific directions. Gain in this sense refers to an increase in

energy in one direction over others.

It should also be understood that gain is not “free”, gain above 0dBi in one

direction means that there must be less gain in another direction. Pictori-

ally this can be pictured as shown in the figures to the right. The orange

pattern represents the radiation pattern for a perfect dipole antenna,

which is shaped like a donut. The pattern for an omnidirectional antenna

with gain is shown in blue. The gain antenna is able to work with a device

located further from the center along the axis of the pattern, but not with

devices closer to the center when they are off the axis – the donut has

been squished.

Gain is also related to the overall physical size of the antenna, as well as

surrounding materials. As the geometry of the antenna is reduced below

the effective wavelength (considered an electrically small antenna) the gain

will decrease. As well, the relative distance between an electrically small

antenna and its associated ground will impact antenna gain.

159 Ort Lane, Merlin, OR, US 97532

Phone: +1 541 471 6256

Fax: +1 541 471 6251

www.linxtechnologies.com

by

Gain Plots

E / Vertical Gain

H / Horizontal Gain

Total Gain

XZ-Plane Gain

YZ-Plane Gain

XY-Plane Gain

Data Sheet ANT-418-MHW-xxx-x