White’s Electronics GM24k, Advanced Manual

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Chapter 4 GM24k Controls
SAT Level
SAT adjust
(hold)
Hot Rocks
Hot rocks are Mineralized Rocks.
They can be heard because they are
different in mineralization than the sur-
rounding matrix or body of ground. Neg-
ative hot rocks, such as magnetite, tend
to give a “boing” sound when the search-
coil is passed over them. The greater the
difference between them and the ground,
the louder the “boing”. Positive hot
rocks, such as maghemite tend to sound
just like any other metal target, such as
a nugget and can give a zip-zip sound.
Positive hot rocks will test any prospec-
tors patience. The GM24k will reduce
the effect and help to identify many hot
rocks. (more on page 18)
V-SAT Speed Control
The Variable SAT (Self Adjusting Threshold)
Speed control adjusts the speed that the GM24k
recovers its threshold hum when the search-
coil passes over changes in mineralization.
This setting is adjusted by holding the MUSIC
button and then adjusting the SAT up or down
between 0 (off), 1 (medium), or 2 (fast). The
letters “Sa” will display when adjusting V-SAT.
VSAT Adjustment
The Initial Setting is 1 (medium), appropriate
for mild-to-moderate ground mineralization.
When you encounter fast changes in ground
mineralization or deeper, larger hot rocks, you
may either get false signals (positive ground)
or lapses in the THRESHOLD hum (negative
ground). Increasing the V-SAT control setting
to
2 will speed up the auto adjustment of the
THRESHOLD “hum” and reduce this interfer-
ence. At the same time, you should slow down
your sweep speed to help SAT do its job to
maintain a smooth threshold.
Remember, overall depth will be diminished
with a faster V-SAT speed, but if the ground is
too noisy to separate a good target from a false
signal, it is better to operate with a little more
V-SAT speed than to lose a target altogether.
This is the same logic that was used in de-
scribing the SENSITIVITY control. Lowering
the gain will reduce overall depth, but by doing
so you can also improve your performance
and find more nuggets in the long run. For
best results, set your V-SAT speed JUST high
enough to cancel out false signals from ground
mineralization and set the SENSITIVITY con-
trol JUST high enough to maintain maximum
depth without having false or erratic behavior.
SENSITIVITY & SAT are like SALT & PEP-
PER. With the right balance the soup tastes just
right.
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