White’s Electronics MXT 300 - Manual (Page 23)

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Chapter 5 MXT 300 Controls
Threshold Control
The THRESHOLD control sets the loudness of
the background "hum" or edge of sound. This
background "hum" should normally be maintained
during 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, chatter or static like but it must be con-
stant so as to not miss that small or deep targets.
At this point, we can't recommend too highly the
advantage of using HEADPHONES. With HEAD-
PHONES you can lower THRESHOLD "hum" lev-
els, you will hear the faintest of target signals while
cancelling out environmental background noise and
improving concentration.
Threshold Adjustment
The MXT 300 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 (edge of sound). If the "hum"
disappears 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, or in the
prospecting MODE you may need to increase the
speed of SAT.
Silent Search
With microprocessor driven THRESHOLD controls
arguably skillful operators can "cheat the system"
and use silent search with high performance results.
Once the threshold is found, edge of sound, setting
the Threshold control slightly counterclockwise
achieves silent search where no threshold hum is
heard during searching. By further optimizing Gain
to radical levels, much of that resulting noise can
be hidden under the Threshold and thus good fi eld
results. Best reserved for more experienced opera-
tors, a balancing act between higher Gain V.S. a
stronger response required to surpass the threshold
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setting, must be achieved and understood.
THRESHOLD CONTROL
“HUM”
Chapter 5 MXT 300 Controls