Fisher CZ-7a PRO Quicksilver Operating Manual page 22

GROUND BALANCING
2. Lower the search coil to an inch or two
above the ground. Now, quickly raise the search
coil. Note that as you lower the coil, the tone
dies out and then gets louder as you raise it.
Finally, the tone returns to normal when you stop
it about 6 inches above the ground. Conversely,
if you set the GROUND control to 1, the threshold
hum gets louder as you lower the coil and dies
out when you raise it.
3. Your objective now is to adjust the GROUND
BALANCE control so that no change, or only a
minimal change, occurs in the volume of the
threshold hum as you bob the coil up and down.
Set the GROUND BALANCE control to 9 and then
lower the search coil and raise it again. As you
bob the search coil, one of three things will
happen to your threshold 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
search coil.
4. If the hum remains the same or changes only
slightly, your CZ-7a Pro is properly ground
balanced and you are ready to begin your
search.
5. If the tone fades as you lower the coil,
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 have gone past the correct ground balance
setting. Increase the GROUND BALANCE control
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