If an antenna is correctly matched to a transmission line, the length of the transmission line:

When an antenna is perfectly matched to the characteristic impedance of a transmission line, all the forward power is absorbed by the antenna and none is reflected back. Because there are no standing waves on the line, the impedance remains entirely constant from the antenna all the way back to the transmitter. As a result, the physical length of the transmission line does not alter the impedance seen at the transmitter end. The distractors mentioning specific fractions of a wavelength only apply when using a transmission line deliberately as an impedance transformer to correct a mismatch.