White’s Electronics Goldmaster GMT - Manual (Page 22)

20
Chapter 5 GMT Searching
Field Use & Tuning Tips
almost impossible to eliminate all of them with one
setting. Some will be identified by the I.D. system
as if they were iron. In every instance, practice
makes perfect. As mentioned earlier, Target Analy-
sis mode ( Trigger Squeezed ) can usuallly make
negative hot rocks disappear. It uses a new method
that hasn't been available before. It is easy to use
and very dependable. Try it, you will like it and
learn to trust it.
Negative Hot Rocks:
Negative hot rocks are ones which would balance
out on Manual GROUND BALANCE by applying
the (+) touchpad and run the GROUND BAL-
ANCES Numbers (type of ground) higher than the
surrounding terrain. They actually produce a null or
no sound when directly under the coil, making a
sound once the coil passes them. This sometimes
sounds like a "boing" when the ground mineral and
the rock mineral are far apart in mineral TYPE,
making them easy to recognize. At any rate, these
are usually black or gray in color and usually
magnetic. When hunting in MANUAL ground
balanc, they can often be tuned out by ground
balancing right over them and then proceeding to
search with the GMT "over tuned" to the ground.
When using this procedure, be sure to search slowly
and keep the coil close to the ground and level.
This will eliminate the bother of such "hot rocks".
Author of "Zip- Zip" Larry Sallee calls these "cold
rocks". They are usually easy to identify. When
using the TRIGGER SQUEEZED in the Iron
Analyze Mode to check them, these Negative Hot
Rocks (cold rocks) will often disappear . If the
ground is littered with these negative hot rocks, not
just an occasional one, the fast AUTOTRAC soft-
ware will realize the negative hot rocks are a bigger
problem than the matrix itself, and will track near
the hot rock balance point, quieting them down a
lot.You may be forced to dial in more VSAT speed
and/or reduce ground penetrating GAIN to keep a
workable THRESHOLD “hum”.
Positive Hot Rocks and Alkalai:
They are usually red or various shades of red to
almost black. They ground balance with the (-)
touch pad. They are sometimes as small as BB's
and sound just like nuggets. These positive "hot
rocks" are almost impossible to tune out and can
tune at very low numbers on the LCD display
meter, near salt. They actually give a positive
signal like metal and that is why they are so hard to
differentiate. Reducing the GAIN and tuning with a
neutral or slight reduction in sound on the down
stroke of the coil during ground balancing can
soften their sound and help to make them less
visible. The Twin D coil on the GMT also helps in
eliminating these pests. Wet alkalai washes can be
extremely difficult to work due to the sensitivity of
high frequency gold detectors to conductive dis-
solved salts and their similarities with the responses
of small gold.
Adjusting GAIN with FAST AUTOTRACK:
If while searching with FAST AUTRACK you
experience erratic behavior such as false signals or
constant beeping and popping, you may be using a
GAIN level which is too high for the ground miner-
alization. Merely reduce the GAIN by turning the
Gain control a notch counter clockwise. Try
searching again. Continue this until you can hunt
without having erratic signals. Your detector is
cancelling ground mineral as you sweep , so you
may notice a slight fluctuation in the threshold hum
as the various ground minerals are tracked out.
Adjusting GAIN in Manual GROUND BALANCE
is done in the same fashion.