On 1/19/11 9:53 AM, Hans Hammarquist wrote:
>
> You can, if you want, view the dipol as two pieces, each with one pole at the
> feeder and the other pole at ground. If the the two part are equal, as we
> intend to have them, the two "hot" poles, will have the same current. If, on
> the other hand, we have an off-center feed the impedances will be unequal and
> the only way to keep the current in he two poles equal is to "force" it with
> an isolating balun such as a current choke.
>
> The current between the antenna wire and ground is, in scientific term,
> called "displacement current". You actually have a current without a
> conductor. That's the same type of current you have through a capacitor.
>
> Hans - N2JFS
>
Only if the feedline is part of the circuit. If you had a asymmetric
dipole, and a tiny battery powered transmitter at the feedpoint, the
currents in the (only) two terminals of the transmitter would be equal
and opposite.
What you describe with displacement currents is where the "antenna"
includes the feedline, and you have the circuit loop is ground: rig:
feedline: antenna: displacement current to ground.
It's when you start putting the feedline (or really, any conductor in
the vicinity) into the system that the issues with asymmetry arise.
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|