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to the audio tones,
noting which targets
produce high and low
tones and how the tar-
get response changes
with discrimination.
As a general rule,
poor conductors
(small nuggets, most
rings, pull-tabs, nick-
els, etc.) should pro-
duce a high tone followed by a low-tone echo. Good
conductors such as large nuggets, pennies, dimes,
quarters, etc. should produce a low tone followed by
a high-tone echo. In addition, most iron will produce a
low tone followed by a high-tone echo, since to a PI
machine, iron behaves like a good conductor.
6. Searchcoil Scanning Technique:
Methodically sweep the searchcoil from side to side
keeping it at a constant height of one to two inches
above the ground. Restrict your sweeping speed
to about 1/2 to two feet per second. Overlap each
sweep by about 1/4 the diameter of the searchcoil.
Try to scan in a straight line (not a wide arc); it helps
keep the searchcoil level, reduces the likelihood of
lifting the searchcoil at the end of each sweep and
ensures the overlap sweeps remain uniform.
18
Figure 16