Delay Line. The XDL20-8-140 is a surface mount delay line that uses a slow wave coupling structure that maximizes the amount of delay per unit area over other distributed delay structures. The XDL20-8-140 can be used in amplifier linearization applications from 1805 – 1990MHz. The XDL20-8-140 is ideal for use in the main loop of feed forward and in pre-distortion amplifiers. The Xinger® delay lines are a low cost, high quality alternative to the traditional coaxial and filter solutions presently available.