"Digging Deeper with the DFX"
Sample 3D Coil Sensitivity Pattern Graph

          "[These graphs] give a good indication of the shape of the sensitivity patterns that emanate below the five White's DFX coils that are currently available [(only the graph from the standard 9.5" coil is shown in this excerpt)].  These graphs are intended to show the relative detection patterns for these coils.
          All of these tests were performed at the same PREAMP GAIN and D.C. SENSITIVITY settings.  These measurement distances, in inches, do not correspond to the maximum distance that the test target was detected.  Instead, the distances shown on the graphs correspond to a measured change in the Non-Motion Mode threshold response (as measured by a voltage from the headphone jack).  These should not be viewed as absolute depth measurements for these coils.  Also, all of the tests are for target-distances of 3 inches and up.  (At closer distances, the coil's sensitivity pattern tends to "pinch in" towards the coil's inner receive winding.)
          All of these graphs show the coil's sensitivity pattern rising upward. In field use, these patterns would project downward into the ground..."

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2004, Jeff Foster