Which of the following is a significant difference between foam dielectric coaxial cable and solid dielectric coaxial cable, assuming all other parameters are the same?
Why Foam dielectric is mostly air with a plastic matrix, so its dielectric constant is lower than solid polyethylene. That raises the velocity factor (roughly 0.78 to 0.85 versus about 0.66 for solid PE) and cuts dielectric losses, so foam cable has lower attenuation per hundred feet. The tradeoff is that the softer, less dense material breaks down at a lower voltage and the center conductor can migrate under compression, so the safe maximum operating voltage is lower.
Watch out Each single-item choice is true on its own, which is the trap: picking just the velocity factor or just the loss statement misses that all three describe foam cable.
Foam = more air: faster (higher VF), lower loss, but weaker insulation. Three true statements means pick them all.