[Elecraft] Magnetic Loop question

[John Magliacane]

On Thu, 10/20/16, Steven Dick <kg4ydw at gmail.com> wrote:

> The vertical loop can be horizontally polarized by feeding it in the middle of the top or bottom edges.   It can be vertically polarized by feeding it in
> the middle of the vertical edges.

That's true for a loop having a full-wave circumference, but "Magnetic Loops" have circumferences that are typically only a fraction of a wavelength, and as such operate under a much different mechanism.

A vertically oriented magnetic loop, regardless of where it is fed, will achieve the highest degree of coupling to a vertically polarized signal, and have a bi-directional (half-wave dipole-like) radiation pattern.

A horizontally oriented magnetic loop, regardless of where it is fed, will achieve the highest degree of coupling to a horizontally polarized signal, and have an omni-directional radiation pattern.

This is because a magnetic loop is most responsive to the magnetic component of the RF wave.

When we speak of RF polarization, we are speaking of the polarization of the electric field.  A vertically polarized signal will have a horizontally polarized magnetic field, and vice-versa.  It is the horizontally polarized magnetic field from a vertically polarized wave front that will cut through the center of a vertically oriented magnetic loop and induce a voltage across its terminals.


73, de John, KD2BD