GM24k Searching
Goldmaster 24k User Manual 19
Backlight and Battery Life
With a short tap of the power button, the
GM24k
’s
backlight will turn on, giving increased visibility
in low light conditions. In bright sunlight it will
not be obvious this backlight is enabled, so there
is a light bulb icon to indicate the status as well
(icon on = light on). This light consumes extra
power, so it is best used only when necessary.
This backlight is on for a few seconds when pow-
ering on the
GM24k
, but only to allow for those
situations when the unit is turned on in total
darkness. It will turn itself off after a few seconds
and the icon will disappear until the backlight is
enabled or the detector is powered back on again.
Operating
GM24k
in Extreme Mineralization:
Thanks to its XGB ground balance, SAT, and
Iron Cancel, the
GM24k
can operate in a wider
variety of conditions than many other VLF detec-
tors. However, it takes some knowledge of how to
use each setting to combat bad ground, and the
differences between types of ground.
In very strong mineralization, such as heavy iron
stone or serpentine, it will be necessary to low-
er the sensitivity. There is enough voltage at the
search coil to cause the
GM24k
to overload in bad
ground, so take some time to find a good setting
for sensitivity before making other adjustments.
To check the ground strength you can enable
Ground Scan by holding the LOCK button.
Another issue you may run into is highly variable
ground mineralization. In these conditions you
will not get an overload response, but will have
to contend with lots of false signals with your coil
sweep. This is a result of the ground phase shifting
rapidly under the coil. The first step you should
take is to increase your SAT setting by holding the
Music Note button, and then tapping the Up but-
ton to set the SAT to a higher setting. This will
allow the detector to adjust more quickly to the
rapid ground changes.
As a last resort, enable the Iron Cancel feature (the
crossed-out nail button). This will not allow those
low-range signals to break through the threshold
in either audio mode. Only in the most extreme
conditions should you adjust the Iron Cancel (by
holding the crossed-out nail button) to higher set-
tings.
Problems from Low Ground Mineralization:
The
GM24k
is designed to work in an environ-
ment of heavy iron mineralization. In some
cases, there may be so little mineralization that the
search-coil will never go quiet as it approaches the
ground. In other words, there never seems to be
any change or only a faint increase in hum as the
coil is pumped. In this instance, lock the ground
balance (lock button) and perform a ground grab
before detecting.
Hot Rocks
The ever-present “hot rock” has caused frustra-
tion with almost every electronic prospector.
Most large ones are on the surface and can be
kicked aside when identified. You will soon learn
what they sound like. The “overshoot” or “boing”
sound will soon become familiar. XGB is really a
good option when they are plentiful. We find it
best to tune to the majority of the ground matrix
and learn what a “hot rock” sounds like. The XGB
of the
GM24k
will recover quickly upon leaving
the vicinity of a “hot rock” and will remain sensi-
tive to gold nuggets. Since there are different kinds
of “hot rocks”, it is almost impossible to eliminate
all of them with one setting. Some will be identi-
fied by the Target I.D. system as if they were iron.
In every instance, practice makes perfect.
