Figure 79. Loop Coupling Compared to Transformer Coupling.
b. If you rotate the secondary winding of the transformer in Part B of
Figure 79, the primary magnetic field cuts the secondary at an angle less
than ninety degrees, and less energy is transferred to the secondary. The
loop in Part A of Figure 79 acts the same way. If you turn the loop at an
angle away from the perpendicular, less energy is transferred.
With a
rotating loop, you can vary the amount of coupling.
Remember, you get
maximum coupling when the loop is perpendicular to, and in the area of,
maximum magnetic lines of force.
c. Maximum magnetic lines of force means that there is maximum current
in this area of the cavity. You already know an area of maximum current has
characterized by the following:
(1) High current.
(2) Low voltage.
(3) Low impedance.
d. A second method of coupling energy to or from a cavity is with a
probe.
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