[Antennaware] End Fed Half-Wave - Area Of Radiation
n6ry at arrl.net
Fri Dec 3 20:12:42 EST 2004
At 12:59 PM 2004-12-03, Dick N3HKN wrote:
>Looking at the 1/2wave antennas from PAR, or others, my question is - what
>portion of the 1/2 wave wire provides the maximum radiation? Is it the end
Just like a center-fed half-wave dipole, the current is maximum at the
center and it's the current that is responsible for the radiation.
There may be a very slight shift of the current maximum if one end is
closer to ground (such as with a vertical or sloper), but it would be hard
to measure in most cases.
Of course, the shield of the coax connected to end-fed antennas (zepps,
J-poles, etc.) usually radiates, too. This depends on the specifics of the
impedance step-up device, the length and routing of the coax, and other
installation variables. Most people don't realize this and it can really
degrade the pattern.
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