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[Local QRM/noise reduction]  [Very small vertical magnetic loop]

[Medium size vertical magnetic loop]  [Vertical magnetic Alford loop]

[Vertical magnetic loops in real life]  [Circular polarization]

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[Dual loop antenna system]  [Hints]

[Phaser 80 – 10 meters]  [Balancing and closed loop antennas]

The very small vertical magnetic loop

In free space

A magnetic loop is called small when the circumference is smaller than 0.1*l.

In that case the polarization in the far field is well known (picture tnx PA3HCD):

Take a good look at the polarization of the far field in each plane. In the YZ-plane it is pure horizontal and in the XY-plane pure vertical polarised. Depending on definition, in the XZ-plane it is also called vertical. On the Y-axis the field is zero !

In free space the very small loop shows a donut shaped field. In every plane with the Y-axis, so also the YZ-plane and YX-plane, the radiation pattern looks like an eight:

Important for QRM reduction is the nulling feature:

• The XY-plane (pure vertical polarization) is the plane of interest.
• Perpendicular to the loop along the Y-axis, the field is zero for the very small loop.
• A horizontal polarised component of a noise source in the XY-plane can not contribute to the signal at all, especially not when positioned on the X-axis.
• The vertical component is nulled only when the source is positioned exactly on the YZ-plane.

Last update: September 24, 2006

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