Measuring the capacitance per unit length of two infinite cones of arbitrary cross section

The capacitance per unit length, and hence the characteristic impedance of two infinite cones, may be accurately measured by employing an extension of conventional guard techniques. An appropriate gap is cut in one of the cones, converting the structure into a three-terminal capacitor. If the arm beyond the gap is long enough, the desired field distribution will be maintained past the gap and the capacitance per unit length of the isolated or guarded section may be measured by a conventional low-frequency capacitance bridge.