Copper-Covered Steel Wire at Radio Frequencies

At radio frequencies the current in copper-covered steel is confined to the copper portion alone; thus such conductors are electrically equivalent to the corresponding copper tubes. The resistance and internal inductance are as low as for solid-copper wire of the same outer diameter. Without sacrifice of conductance, as much as three fourths of the copper that would be required for a solid-copper conductor can be saved by using copper-covered steel; that is, by the partial substitution of steel. Alternatively, the amount of copper required for a solid conductor can be utilized in copper-covered steel to give a conductor with about half the resistance of the solid-copper wire, and with greater mechanical strength. In general, these observations hold at radio frequencies, but the frequency at and above which they apply depends upon the size of conductor considered. Curves are given to compare the resistance and inductance of copper-covered steel and solid copper over wide ranges of frequency and sizes of conductors.