"Tak"wrote
Need a graph of impedance (both R and X) relative to off-center
distance on a half wave dipole.
Anybody have ot handy? Searched on web and books but could not find.
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You're looking in the wrong places. Even Terman and probably Kraus are
silent.
The input impedance of an off-centre fed 1/2-wave dipole is always purely
resistive (because the antenna is resonant), with approximately -
R = 73 divided by Square( Cosine( Theta ) ) ohms.
Where Theta is the angle 180 times D divided by L degrees,
D is the distance from centre and L is the overall length in any units you
like.
But, be warned, if not at the centre, as soon as you connect your feedline
you will make a mess of it depending on height and on length and impedance
of the line. The feedline becomes a part of a far more complicated antenna.
On the other hand, the approximation is good enough for other calculations
provided the connection is, say, not more than 1/2 of the way to the end of
the wire.
You will have to plot your own graph. ;o)