Bobbing - Fisher CZ-20 Quicksilver Operating Manual

GROUND BALANCING

BOBBING

1. 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 3 feet away from any metal
objects. Do not use the PINPOINT button during any
part of this procedure.
2. Lower the coil to an inch or two above the
ground 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 to12 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.
3. Your objective now is to adjust the GROUND
control 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:
1) It will fade again as you lower the coil and
increase as you raise it.
2) lt will get louder as you lower the coil and go
silent as you raise it.
3) The hum will remain the same, or if it changes
slightly, the change is the same whether you lower
or raise the coil.
4. If the hum remains the same or changes only
slightly (as in step 3 above), your CZ-20 is properly
ground balanced, and you are ready to begin your
search.
5. If the tone fades as you lower the coil (as in step
1), 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.
6. If the hum gets louder as you lower the coil, you
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