[Elecraft] RF on pipes

[Geoffrey Mackenzie-Kennedy]

Evening Fred,

If the pipe is OPEN at its ends, would not the current flowing on the 
outside of the pipe "fold over" at the end of the pipe and continue to flow 
on the inside skin? The reverse, if you like, of the situation where a coax 
feeder is used to feed a dipole / doublet.

73,
Geoff
GM4ESD


On July 09, 2011 at 18:17 Z, Fred Jensen wrote:

> 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.