b) Null Detection Method
Also called “centering,” tracing a line by finding points
where the signal vanishes (“nulls”) is an alternate method
to peaking. Because the receiver relies on a directional
antenna, positioning it so that the front panel perfectly
faces the line will cause it to detect no signal. Using nulls
over the line, the operator can ascertain the precise loca-
tion of a line below the surface, as well as determine its
depth.
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