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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]

[Broadband amplification] [Broadband amplifier] [Single chip amplifier]

[Dual loop antenna system] [Hints]

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


Broadband amplification


Broadband amplification for a short (capacitive) dipole is well known.

The same is possible for a magnetic loop, however with a different amplifier.

The loop is shown as an inductor La and the induced signal voltage as a source Va.

The output voltage is easily calculated:


The induced voltage Va:


E [V/m] is the electric field, A [m2] the surface of the loop, c the speed of light and ω the frequency times 2π.

So the output voltage Vo is:






Loop electrical behaviour

The loop however behaves only at low frequencies like an inductor.

The next schematic shows a better way of modelling the loops (values indicative).



Design of the loop

The loop can be a circle or a square, it can be made with tubing or with a thin wire.

What counts is:

or more practical:


For example: a circular 1.35m diameter loop with a 10mm diameter tube is equal to a 1.351.35m square loop with a 2mm diameter wire.


Observe that the resistance of the wire is not in the equations. Normally the resistance is much smaller than the ωLa and can be neglected.

(when loops are tuned by a capacitor in a small band application, then the loss resistance counts)




Last update: September 24, 2006