# Affects of various building materials on balanced transmission line?

Is there a significant change in impedance, and/or loss, when balanced transmission line is placed through non-metallic building materials, e.g., plaster, gypsum wallboard, wood, or cementitious siding?

• Just to be sure: when you say "balanced transmission line", you mean something like a ladder line, and not, say, twinax or twisted pair in an Cat.5e network cable? Commented Jul 31 at 9:14
• Yes, most likely 450Ω ladder line. And as an aside, I'm considering drilling holes to run stainless steel, or aluminum bolts through, calculating the distance between the two bolts using a balanced line calculator, to maintain the 450Ω impedance. But I am interested to see if anyone has had any challenges with bringing balanced line into a mostly wooden structure, and how they over came the issue. Obviously keeping a distance from metallic objects, like nails and aluminum gutters, is important, but I figure that's a given in my question. Commented Jul 31 at 10:41
• Agreed, that's a given. Generally, what you describe sounds very feasible – you'll need an estimate for the epsilon of your building material (and you need that to remain constant), but the thinner the wall is relative to wavelength, the less it really matters. And the smaller the structures inside the wall relative to the wavelength, the less it matters whether it's homogeneous or you just use the average epsilon as if it were. But quite honestly, two holes instead of one, that does sound like a lot of Commented Jul 31 at 10:55
• but truth be told: two holes sounds like more work (and more trouble keeping the wet outside, temperatures inside, and the wall in a reliable state of moisture) than adapting to a shielded transmission line, before and after the wall, and just putting that through a single hole. I haven't done the math, but I imagine two coax cables with their outer conductors touching reliably (so, maybe in a heatshrink tubing?) could make for a reasonable balanced transmission line with much less of the effects of the surrounding material. (really, I'd need to sit down and think this through). Of course, at Commented Jul 31 at 10:56
• @LouisSeaman the details in your comments should be in the Question so it doesn't get lost. Commented Jul 31 at 13:18