Orientation of loop antenna (receiving mode)

Question

I have done some measurements through a loop antenna similar to that shown in the following picture (all the information included does not refer to my antenna, it is a picture used only to show its geometry):

My professor has told me that this antenna was sensitive to the electric field orthogonal to the surface of the loop.

I have the following questions:

• Is this true for any loop antenna? Or does it depend on the specific model I use?

• How can I understand which the direction us of the electric field which is "caught" by an antenna? I thought to use the radiation pattern, but then I thought that it refers to how it catches power, while I want some information about the electric field.

Answer 1

Since the EM waves are radial to line of sight and never longitudinal, it is the viewed effective aperture geometry of the antenna relative to \$\lambda /2\$ that permits matching the impedance or transferring RF power to a load.

Thus when you see no aperture rotated by 90 deg now inline with line of sight, you can expect a null in the aperture and signal and thus only get fringe signals from reflections or nothing.

This also applies to a dipole. Staggered dipoles in parallel are called a Yagi antenna.

The geometric ratio of conductor, l and gap, g of the return current determines the cable impedance. e.g. 200 vs 75 vs 50 Ohm as well as the Dk between them.

If signals are broadside to the antenna then the radial EM fields can induce a longitudinal current.