Bobbing" The Search Coil Method - Fisher M-Scope CZ-5 Quicksilver Operating Manual

"BOBBING" THE SEARCH COIL METHOD

This method takes a little more practice, but you may find it
slightly more accurate (fewer false signals from ground minerals)
in very highly mineralized ground (as in the note above), or if
you are searching in the Autotone mode.
1. Set as in the "Turn-On" procedure, making sure the
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.
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 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.
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) It 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 3) above, your CZ-5 is properly ground balanced,
and you are ready to begin your search.
5. If the tone fades as you lower the coil as in 1),
continue to lower the ground balance setting in small
increments until the threshold hum remains the
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