Windowed ladder line – single core CCS 21% IACS

There is some evidence that the common 1.024mm (#18) single core CCS windowed ladder line advertised as 30% IACS conductivity supplied recently may be closer to 21%. This is based solely on comparison of measured DC resistance with specification, but that is a strong hint that the copper cladding is less than specification.

Theoretical prediction

This article presents a theoretical prediction based o A model of current distribution in copper clad steel conductors at RF of the matched line loss (MLL) at 1.8MHz.

The assumption is a 1.024mm steel cored conductor with 30.7µm copper cladding.

Above is a plot of the predicted current magnitude and phase distribution in the conductor.

From that, we can calculate the expected MLL to be 0.00405dB/m, 66% higher than we would expect of a solid copper conductor of the same diameter.


Of course credible measurements are of greater value than simply theoretical predictions, and there may be good reasons why real product varies from theoretical.

John Oppenheimer, KN5L, has made measurements of two different samples of cable marked JSC 1318 and reported MLL @ 1.8MHz of 0.0049dB/m in both cases.

Theory vs measured

To the point of theoretical vs actual, note that this product is advertised as 30% IACS cladding which would suggest MLL should theoretically be 0.00241dB/m @ 1.8MHz, a long way short of the measured 0.0049dB/m. The measured DC resistance strongly hints a likely reason for serious departure from theoretical.

The expected loss of 1.024mm (#18) 21% IACS cladding is similar to a solid copper conductor at 7MHz and above, and poorer below that frequency.

Note that the results here cannot simply be applied to the more popular stranded CCS types of line, they are significantly worse MLL due to the thinner copper that accompanies stranding.

The burning question is, what do you actually get when you buy these windowed ladder lines?