Fisher M-SCOPE CZ-3D Operating Manual page 11

"BOBBING" THE SEARCH COIL METHOD
1. Set as in the "Turn-On" procedure, making sure the
2. Lower the coil to an inch or two above the ground
3. Your objective now is to adjust the GROUND control
C The hum will remain the same, or if it changes
4. With a little practice, you should be able to ground
DISC control is at AUTOTUNE and the SENSITIVITY
control is set so you can just barely hear a threshold
hum. Hold the search coil parallel to and 6 to 12
inches over the ground and at least three feet away
from any metal objects. Do not use the PINPOINT
button during any part of this procedure.
and then quickly raise it. Note that as you lower the
coil, the tone disappears, then gets louder as you
raise it and finally returns to normal when you stop it
6 to 12 inches above the ground. Conversely, if you
set the GROUND control to 1, the threshold hum will
get louder as you lower the coil and disappear when
you raise it.
so that there is no change, or only a minimum
change in the threshold hum, as you move the coil
up and down. Start by lowering the GROUND control
to 9. Lower the coil and raise it again. One of three
things will happen to your theshold hum:
A It will fade again as you lower the coil and increase
as you raise it. Continue to lower the ground
balance setting in small increments until the
threshold hum remains the same (or changes very
little) as the coil is lowered and raised.
B It will get louder as you lower the coil and go silent
as you raise it. Increase the ground balance level
(rotating the control counterclockwise) in small
increments until there is little or no change in the
threshold level.
slightly, the change is the same whether you lower
or raise the coil. Your CZ-3D is properly ground
balanced, and you are ready to begin your
search. You have gone past the correct ground
balance setting.
balance quickly by "bobbing" the coil up and
down in a continuous movement as you adjust the
GROUND control with your thumb.
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