with outer conductor 15 block number 25 acts as a positioning member for precisely positioning the coupler against the end of microstrip 55 thus the coupler position in relation to the adjacent end of the microstrip line is determined by the block member 25 block member 25 also provides a convenient means to securely affix the coupler to the microstrip conventional screw members 70 may be inserted through holes in the block member for disposition into microstrip support layer 62 block member 25 also provides electrical continuity with microstrip lower conductor 68 as a further positioning means block 25 is preferably provided with registration shoulder 28 shoulder 28 may be an extension of cylindrical outer conductor 15 with the portion thereof removed below a chord extending parallel with upper surface 63 of microstrip substrate 60 the removed portion extending back to block 25 thus registration surfaces 29 are formed for providing precise registration of the coupler relative to the upper surface 63 of substrate 60 the step defined by surfaces 29 and the adjacent surface of block 25 thus precisely position the coupler in relation to the microstrip line as will be apparent from the above discussion the electrical performance of the coupler is dependant upon accurate offset positioning of the inner.