Hot Rocks; Variable Sat Speed Control; Vsat Adjustment - Whites GMT Manual

VARIABLE SELF
ADJUSTING SPEED
CONTROL (VSAT)

Hot Rocks

Hot rocks are Mineralized Rocks.
They can be heard because they are
different in mineralization than the
surrounding matrix or body of ground.
Negative hot rocks, such as magnetite,
tend to give a "boing" sound when the
searchcoil 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 prospectors patience. The GMT will
reduce the effect and help to identify
many hot rocks. (more on page 18)
Chapter 4 GMT Controls

Variable SAT Speed Control

The Variable SAT (Self Adjusting Threshold)
Speed control knob adjusts the speed that the GMT
recovers its threshold "hum" when the search-coil
passes over changes in mineralization. Changes in
mineralization can cause a rise or fall in the "hum".
This can disrupt the smoothness of the threshold
and thus obscure or hide the signal from a target.
A slow, wide sweeping search coil swing gives the
GMT enough ground sampling to maintain the
THRESHOLD "hum". This steady "hum" helps you
concentrate on the "zip-zip" sound of a metal target.

VSAT Adjustment

The Initial Setting Triangle is set between 3x and
4x on the control knob, appropriate for 80% of
hunting locations. 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 speed up the auto adjustment of the
THRESHOLD "hum" will reduce this interference.
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 describing the GAIN control. Lower-
ing 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
GAIN control JUST high enough to maintain
maximum depth without having false or erratic
behavior. GAIN & SAT are like SALT & PEPPER.
With the right balance the soup tastes just right.
11