What the heck is gain, anyway?
Think of a radio signal being a ball of radio waves being emitted from a single point. By reshaping the signal you add gain, or power, to the signal strength. In the case of an omni-directional antenna, the top and bottom of the ball are squished down and up to flatten out the signal, creating a doughnut shaped pattern. In the case on a Uni-Directional antenna, the signal is reshaped by not only squishing the top and bottom, but by changing the shape as well. Imaging looking down on the ball and being able to cut into the six o’clock position and then reshaping it so it looks like a piece of pie with the left edge at 10 o’clock and the right edge at 2 o’clock. In each case the total power is compressed into a tighter pattern thus resulting in a gain of the effective strength of the signal.
