[Antennaware] End Fed Half-Wave - Area Of Radiation

[Terry Conboy]

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 
>third?

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.

73,
Terry N6RY