CISPR 22: 1997 conducted emission on telecom ports products pass/fail depending on test method

This paper analyzes test result differences for emissions testing in accordance with CISPR22: 1997. Emphasis is laid on unshielded twisted pair cables. It shows potential errors due to imbalance in coupling of the capacitive clamp to the wires of a differential pair and the influence of the common mode source impedance on current clamp and ISN measurements.