On 10/10/2014 10:04 AM, Lostgallifreyan wrote:
"J.B. Wood" wrote in
:

The small loop is assumed to lie in the x-y plane of an x-y-z orthogonal
Cartesian coordinate system where theta and phi are the angles measured
from the z-axis and x-axis, respectively.


Just two axes? I've been asking on and off for advice on something... I was
shown a nice design for a loop a few weeks ago, it was a helix, so in 3 axes.
What advantage if any does that give over a loop in only two axes? As a guess
I'll suggest it offers finer directional selectivity, but I'm hoping someone
who really knows about this can tell me.

Hello, and the small loop of uniform current is assumed to be lying flat
in the x-y plane. Textbooks do this to facilitate/simplify calculation;
the loop could be oriented in any direction (which is what would happen
if we rotate the original xyz orthogonal axes to some new xyz axes but
keep the loop stationary).

The E and H far-field formulas I previously provided give magnitude and
direction of these vectors using spherical coordinates (r, theta, phi)
relative to a Cartesian system. If you don't understand coordinate
systems and vectors then I can see why you might be confused.

Oh yeah, and one other thing that often escapes folks: You can't radiate
either an E or H field by itself. The other component is always
present. That's why we talk about the propagation of electromagnetic
waves/photons. Sincerely,

--
J. B. Wood e-mail: