[TowerTalk] Balun question shield leakage

[Jim Lux]

At 01:53 PM 6/14/2007, Tom Rauch wrote:
> > Anything is possible, of course, but coax would have to be
> > pretty awful for
> > enough field from the differential signal to cause
> > significant heating.
>
>"Unlikely" isn't strong enough, it would be impossible.
>
>I can buy the cheapest radio shack coax, the type that you
>can see through the shield to the center dielectric, and it
>is nearly impossible to measure the leakage through that
>shield unless I use special equipment.
><snip>



>Let's not obsess about things that don't mean anything. Let
>the Audio-phools and CBers worry about those shields.

I suspect that a crummy shield would have a larger effect on IR 
losses than on anything else.  But, since the surface area of the 
shield is so much larger than the center conductor, I would think 
that the center conductor dominates. For foamed dielectric, I think 
75 ohm cable is around 5:1 diameter ratio, so the shield only 
contributes 15-20% of the loss.  For 50 ohm cable, the ratio is 
smaller, so the shield loss would be more important.