Re: Steel core elements

A steel core wire (copperclad) should behave almost the same as a
solid copper wire at any frequency above about 1 MHz. This is true
for two reasons:

  1) Permeability of a ferromagnetic material is a function of
     frequency. For rolled steel, the permeability becomes about
     the same as copper at around 500 kHz.

  2) Skin effect will push most of the current into a very small
     annular ring around the outside of the wire in any case, especially
     at VHF frequencies.

The only possible difference at low frequencies (1 MHz to 10 MHz) might
be the lower DC conductivity of steel as opposed to copper. This might
cause slightly more loss per unit length; however, this is quickly
overwhelmed by the AC conductivity caused by skin effect.

Conclusion: In my opinion (whatever that's worth), copperclad wire
should behave electrically almost identically to solid copper wire at
HF and certainly VHF and higher frequencies.

Cliff Kraft
AT&T Bell Laboratories
cliff_at_ihgp7.att.com
Received on Tue Feb 06 1996 - 16:49:00 EST