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Chapter 4 GMT Controls
Threshold Control
The THRESHOLD control sets the loudness of the
background "hum". This background "hum" must
be maintained at ALL times when searching. In
order to hear the tiniest and deepest targets the
THRESHOLD "hum" should be set at the faintest
audible level. It can be slightly scratchy, chattery or
static like but it must be constant so as to not miss
that small nugget in a silent spot. At this point, we
can't recommend too highly the advantage of using
HEADPHONES in your prospecting. With HEAD-
PHONES you can lower THRESHOLD "hum"
levels, you will hear the faintest of target signals
while cancelling out environmental background
noise and improve concentration.
Threshold Adjustment
The GMT has an improved microprocessor driven
THRESHOLD control that is adjusted with a single
turn. It does not, therefore, require a 10 turn pot for
precise adjustment. Digital software provides much
higher resolution, thus you can set the "hum" faster
and more accurately. Set the knob all the way to
the left or counterclockwise and then rotate it
clockwise until the faintest audible level of "hum"
is attained. If the "hum" disapears for any
reason(other than bumping the control) you may be
either swinging the coil too fast or your GAIN
control is set too high.
THRESHOLD CONTROL
“HUM”