Low passive intermodulation coaxial connector test interface

A coaxial RF test connector comprises an inner conductor and an outer conductor arranged coaxially with respect to a center axis. The outer conductor includes a groove dimensioned to hold a circularly shaped contact spring. The contact spring includes a base portion and a plurality of arc-shaped contact fingers extending from the base with gaps between the individual contact fingers. The base has a radius larger than that at which the contact fingers are bent. The contact fingers have first contact section for contacting the outer conductor of a compatible coaxial connector in a direction radial to the center axis, and a second contact section for capacitively coupling to a sidewall of the groove.