What antenna matching system matches coaxial cable to an antenna by connecting the shield to the center of the antenna and the conductor a fraction of a wavelength to one side?
Why The gamma match is the unbalanced (coax-friendly) feed for a grounded-center driven element: the braid bonds to the element's center, which is a voltage null and can be at boom/ground potential, while the center conductor runs through a series capacitor to a gamma rod that taps the element a short distance out to one side. Moving that tap point out from center finds a spot where the resistive part matches 50 ohms, and the series capacitor cancels the added inductive reactance. It is the standard driven-element match on Yagis fed with coax.
Watch out The T-match is the same idea but symmetric, with rods tapping the element on both sides for a balanced line, and the delta match spreads a balanced line open into a triangle touching two points either side of center; neither uses a single one-sided tap with the shield at the middle.
Gamma = Greek letter with one leg off to the side; T-match has two legs, delta is a triangle.