Re: NEC-LIST: Low angle radiation?

David,

You made a good point that two opposite polarity accelerating charges
could radiate without a middle section using the pithball
example. From aperture theory, a discrete aperture distribution is
equivalent to a continuous aperture distribution if the sampling
occurs frequently enough along the length of the aperture. However,
how can the ends of a dipole without the middle section be fed? Since
a middle section has an alternating current maximum (accelerating
charges), it too should radiate.

One practical example of antenna that does radiate from the ends is a
microstrip antenna operating in the dominant halfwave mode. However,
the middle section would also have some radiation if the transverse
fringing electric fields on both sides of the middle section of the
strip did not cancel out.

For these reasons, I believe that the entire length of the dipole is
responsible for radiation.

Sincerely,

Roland Mueller

> Hold on. Aren't the Q and I out of phase? The Q peaks at the end as
> the I goes through a zero. There is transport of charge such that the
> ends of the dipole are alternatively +/-q and -/+q. Thus radiation
> results. Two charged pith balls (one +q and the other -q), stuck them
> to the ends of an insulating stick and twirled it around you'd get
> radiation too (it would have higher order multipoles than just dipole
> though). No standing wave needed.
>
> -David Fluckiger
Received on Sun Feb 20 2000 - 15:21:50 EST