An impedance adapter with body and cap portions coupled together encloses a cavity with a printed circuit board (PCB). The PCB is provided with a trace on a first side and a ground plane on a second side. The trace is coupled to a first contact at a first end of the PCB and a second contact at a second end of the PCB. The trace has a sinuous path between the first contact and the second contact, the path longer than a longitudinal axis length of the PCB. The first and second contacts are supported coaxial within the inner conductor bore of the respective cap portion and body portion by first and second end insulators. The ground plane coupled to the body portion and the cap portion. A method of manufacture for the adapter includes steps of pre-assembling the PCB, contacts and insulators before insertion into the cavity.