[Elecraft] RF on pipes

[Fred Jensen]

On 7/9/2011 10:02 AM, Clint wrote:
>
> ANYWAY, I know that RF "travels" on the outside skin of a conductor.
> My question is: Does it also travel on the inside skin?

Only if you "inject it there [e.g. a copper plug into the end of the 
pipe that connects with the inside only].  Similar to coax which 
actually exhibits 3 conductors ... the center, the inside of the shield, 
and the outside of the shield.  We suppress currents on the outside with 
baluns at the antenna feedpoint.

A small amount will of current will appear on the inside of the pipe due 
to inevitable stray couplings even if you "inject" the RF onto the 
outside only.

> In other
> words, would the impedance be the same on a round hollow tube as it
> would be if the tube was slit and laid out flat?

No.  A flat strip has it's own impedance characteristics.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2011 Cal QSO Party 1-2 Oct 2011
- www.cqp.org