Owen Duffy wrote:
On Wed, 05 Oct 2005 19:56:48 GMT, Ed
wrote:


Dumb sounding question----but-----with a ladderline fed dipole, is the
feedline supposed to radiate and be part of the antenna, under some
conditions?


NOT a dumb question. I was always under the impression that radiation

from the two parallel wires in ladderline was supposed to cancel itself

out... ergo no radiation. That's why they call it a balanced feedling.



Ed, your unstated assumptions is critical to the correctness of your
statement.

At sufficient distance from the parallel line, the fields from each
conductor are canceling providing the currents in each conductor are
exactly equal in magnitude and exactly opposite in phase. Under those
conditions, the parallel line is also balanced feed line.

Achieving those conditions (or a sufficient approximation) doesn't
happen automatically in the real world. There are all manner of things
in practical applications that would cause unbalance in the currents
in the conductors.

If the currents are not balanced, the fields will not cancel, and
there will be radiation to some extent, so the feed line does indeed
become part of the radiating system to some extent. Conversely, feed
line capture would contribute to some extent to received energy.

Owen
--

Would twisting the ladder line help?

--
William Warren

(Filter noise from my address for direct replies)