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
-----Original Message-----
From: jimlux <jimlux@earthlink.net>
To: towertalk <towertalk@contesting.com>
Sent: Wed, Jan 19, 2011 12:09 am
Subject: Re: [TowerTalk] current balance in ladder line?
On 1/18/11 8:46 AM, Andy wrote:
> Why is the current into the antenna balanced?
Well, it isn't always. You are right to question that assumption.
If there's only two terminals, the current is, by definition, balanced
t that point.
What might not be balanced is the current *distribution* and any
urrents that are induced on nearby objects (e.g. the outside of the
hield of the feedline, or common mode current in a balanced line)
>
An OCF (off-center fed) dipole does not have balanced currents at the
feedpoint,
Not true, from basic circuit theory. *at the feedpoint* the current
nto one terminal will be exactly the opposite of the current into the
ther terminal.
What's not symmetric is what happens after that. The current
istribution will likely not be symmetric, so any conductor in the
icinity will see a different contribution from the two sides, and, so,
ill have some current induced in it.
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