What impedance does a 1/8-wavelength transmission line present to an RF generator when the line is shorted at the far end?

The impedance presented by a mismatched transmission line changes periodically with its length. For a line shorter than a quarter-wavelength (such as a 1/8-wavelength stub), the impedance transitions gradually into a pure reactance rather than instantly inverting. When starting from a short circuit (zero impedance) and moving toward the generator, the phase shift causes the line to store magnetic energy, making it exhibit inductive reactance. It has not yet reached the quarter-wave point where it would become a high-impedance open circuit. It is helpful to memorize the rule of thumb for stubs less than 1/4-wavelength: a shorted stub acts like an inductor, while an open stub acts like a capacitor.