>
>I think most of the NEC based programs calculate the current distribution
>along the length of the antenna's linear elements. The far field pattern
>of the
>antenna can then be derived by integrating the field contributions of each
>elemental portion of that distribution. The equations given in Kraus's
>"Electromagnetics" 2nd edition express the E and H fields in the far field
>in terms of the current distribution only. His text does mention that the
>E field depends on both current and charge distribution, but that only the
>current distribution needs to be considered in the far field.
>
>A 1/2 wave dipole can be thought of as a bunch of short linear dipoles
>placed end-to-end with the current in each short dipole element proportional
>to the magnitude of the dipoles familiar half sinusoidal current
>distribution at that point along the length of the antenna. The short dipole
elements
>near the
>center of this array will of course contribute more to the overall radiation
field
>than the ones near the ends since the current will be larger in the elements
>near the center than that of those near the ends.
>
>If I had the choice between having the ends of my dipole high with the center
>low versus having the center high and the ends low, I would choose the latter
>option.
>
// It takes volts and amperes to make the E-field and it takes volts and
amperes make the H-field. Eliminate one and EM radiation is none. I
used to get involved in 40m daytime shootouts between Las Vegas and L.A.
The consistent winner was a flat-top dipole.
cheers, Mike>
>
>----- Original Message -----
>From: "2" <2@vc.net>
>To: "Ron Lile" <rel@rnet.com>; "at towertalk" <towertalk@contesting.com>;
>"1topband mailing-list" <topband@contesting.com>
>Sent: Sunday, September 02, 2001 9:18 PM
>Subject: Re: [TowerTalk] True or Not True?
>
>
>>
>> >
>> >Several papers have been published lately that attempt to explain the
origin
>> >of radiation from a dipole.
>> >
>> >The papers are saying that the primary radiation on a dipole come from the
>> >middle (the high current point) AND the ends.
>> >
>> // I used to think that the radiation mostly came from the current
>> portion of an antenna. However, the University of California currently
>> teaches that all parts contribute equally. Electro Magnetic radiation -
>> a.k.a. photons - consist of an electrostatic E-field and a perpindicular,
>> electromagnetic H-field. The higher-voltage ends contributes most to the
>> E-field and the higher-current center contributes most to the H-field.
>> -- Congrats Ron Lile, KØRL, you were the only one who agrees with the
>> University of California.
>> cheers
>>
>> >The papers have been publish in the Journal for the Antennas and
Propagation
>> >Society of the IEEE. I need to look them up again in the library. They are
>> >recent issues.
>> >
>> >Ron , K0RL
>> >
>> >
>> >----- Original Message -----
>> >From: 2 <2@vc.net>
>> >To: at towertalk <towertalk@contesting.com>; 1topband mailing-list
>> ><topband@contesting.com>
>> >Sent: Sunday, September 02, 2001 9:39 AM
>> >Subject: [TowerTalk] True or Not True?
>> >
>> >
>> >>
>> >> Does radiation come mainly from the high-current portion of an antenna --
>> >> i.e., for a half-wave, from the center?
>> >>
>> >> - R. L. Measures, 805.386.3734,AG6K, ... ...
- R. L. Measures, 805.386.3734,AG6K, www.vcnet.com/measures.
end
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