antenna-theory.com

[btb4198]

ok so the r in R<< D is the radius of what? radius of antenna ? or radius of something else ?

[Schubert]

It is R >> D.

R is the distance from the antenna where you are measuring the fields transmitted from the antenna.

R>>D is one of the requirements to be in the "far field" of the antenna. This means that if the antenna is of size D, then to be in the far field you must be at least 10*D away from the antenna. Note that this is only one of the requirements to be in the far field, all 3 conditions must be satisfied:
http://www.antenna-theory.com/basics/fieldRegions.php

[btb4198]

D is the length of the antenna right?
R >> D
178m >> 0.03125m is true

R >> λ
178m >> 0.125 is true

R > ( 2D^2)/λ

178m > 0.015625m is true

so my point is in the Far Field, right?

[bigSteve]

Yes, all the requirements are met to be in the far field.