White’s Electronics Goldmaster GMT - Manual (Page 11)

9
Gain Adjustment
(cont'd)
REDUCE GAIN" message is flashed, you must
heed it and reduce the GAIN rather than raise it.
3. The object of increasing the GAIN is to get the
maximum available depth from the detector WITH-
OUT causing the "BAD GROUND" message to
appear, which indicates an overload of the circuit.
4. In addition, any increase in GAIN adjustment
should NOT BE at the expense of maintaining a
smooth and constant THRESHOLD "hum". False
signals, beeps and bops from bits of mineralization,
erratic behavior, and lapses in THRESHOLD all
can be the result of running with too much GAIN.
5. The use of the VSAT (variable self-adjusting
threshold) control will also help to maintain a
smooth THRESHOLD "hum" and will be covered
in a later section.
6. While using a steady slow search coil sweep
speed, advance the control towards "10" while
maintaining a quiet smooth background THRESH-
OLD "hum". If the "BAD GROUND-REDUCE
GAIN" alert keeps popping up on the display or if
ground noises are still a problem reduce GAIN.
7. The IRON ID capability of the GMT also
functions more accurately when the GAIN is set at
a level which allows for smooth operation. Too
much GAIN can cause bad ground to distort the
proper identification of iron and non-iron targets.
In addition, just as a slow, broad search-coil speed
will maintain smooth threshold, it will also allow
the search-coil to get clear off of the target with
each pass, thus insuring that the GMT "sees"
ground as well as target. This is essential for the
accurate operation of % of Iron Probability ID.
FAST AUTOTRAC
POSITION
ON GROUND BALANCE
TOGGLE SWITCH
VSAT SPEED CONTROL
IRON I.D. BARGRAPH
Chapter 4 GMT Controls