On 6/30/08, Steve S. Bosshard (NU5D) <[EMAIL PROTECTED]> wrote: > Aside from the losses mentioned earlier in coaxial cable, (IR loss, > Dielectric Losses, and Radiation) under radiation, aside from the > percentage of shielding, the resistivity of the shielding also comes > into play: > > "For shielding to work perfectly, the shield conductor must have no > resistance. If you look up the skin depth formula, one of the terms is > sigma, the conductivity of the material. If sigma is small, the skin > depth gets big. > > John" > > > So 100% shielding does not mean 100% containment, necessarily. > > 73, Steve NU5D > Yes. And if you talk with the cable companies about how they compute their claimed shielding percentage and shielding effectiveness, you'll find they all use different formulas. Also, none of the companies I've talked with would reveal the formula they use.
This also means it's not a good idea to compare coax across brands. Shielding effectiveness comparisons within one manufacturer's line are probably okay. But the numbers for one brand don't necessarily mean the same thing as the numbers from another. More is better, but that's all we can say. This is all based on a coax comparison project we did for a nationwide retailer a few years ago. Brad, KV5V
