Headphones; Quick-Start Demo - Fisher Labs Gold Bug DP Owner's Manual

QUICK-START DEMONSTRATION
IX. Press-and-hold and hold the nickel over the searchcoil
a. Notice that motion is not required.
A motionless object induces a hum.
b. Notice the variable pitch & volume hum.
c. Move the nickel closer to and farther away from the searchcoil.
Notice the changing "depth" values.
X. Click the MODE knob to the right.
The detector is now in the ALL-METAL Mode
a. Keep GAIN set at the 12:00 position
b. Rotate the THRESHOLD knob slowly from the far counterclockwise
position to the full clockwise position.
Notice these attributes of the THRESHOLD control, with no metal
over the searchcoil.
i. at low settings you will hear no sound
ii. at mid-scale, there will be a transition point from no sound to
a barely audible, choppy sound.
iii. at full scale you will hear a loud, constant tone. It may also have
an irregular or choppy sound, as a result of electromagnetic
interference emitted from other electrical devices.
Use with headphones
The Gold Bug DP is equipped with both a 1/8" and 1/4" headphone jack. Any
headphones with a stereo plug will work; headphones with a mono plug will not
work. Using headphones extends battery life, and also prevents the sounds from
bothering bystanders. It also allows you to hear subtle changes in the sound more
clearly, particularly if searching in a noisy location. Gold nuggets are often very
small, so closely monitoring changes in sound using headphones will improve your
gold prospecting results. For safety reasons, do not use headphones near traffic
or where other dangers, like rattlesnakes, are present. This device is to be used
with interconnecting cables/headphone cables shorter than three meters.
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ELECTRICAL INTERFERENCE (EMI)
EMI is usually easier to control in the All-Metals mode than in the Discrimination mode.
On the Gold Bug DP, setting the discrimination level between 60 and 70 will usually
reduce interference. In the Discrimination mode, the detector may chatter if the
searchcoil is not in motion, but once you start sweeping it over the ground, the signal
from the ground will usually suppress the EMI chatter, except for an occasional pop or
click which will not sound like a real target.
If you are conducting an indoor demonstration, you may find that changing the
orientation of the searchcoil will reduce the pickup of EMI.
If you carry a cell phone or other high-tech electronic equipment while metal detecting
and you encounter EMI, try turning the device off and see if that solves the problem.
Turn such devices completely off, not just into standby mode.
When working near overhead power lines, you may get the best results right under the
power line and the worst results when standing at a 30° to 45° angle to the power line.
Many sources of EMI are intermittent. You may find that an area which is difficult to
search at one time of day may be easier after 5 PM, or on weekends. Power lines are
usually quietest late at night, and on weekend mornings.
Small searchcoils usually pick up less EMI than larger searchcoils. On a site with severe
electrical interference, a small searchcoil is often a better choice than a large one.
Distinguishing Electromagnetic Interference from other problems
EMI will often vary as you walk around from place to place, and it will also vary with
changes in the orientation of the searchcoil. This is almost never the case if there is a
functional problem with the metal detector itself.
The most common cause of a noisy metal detector, where the problem is not EMI, is a
defective searchcoil. If striking the searchcoil with your hand causes the noise to start
or stop, the problem could be a defective searchcoil. Also, a defective searchcoil often
causes noise of a more intermittent nature than electrical interference.
The second most common cause is a loose searchcoil connector. The noise from a
loose connector will usually be very erratic or intermittent in nature. Try unplugging the
searchcoil and then reconnecting it to ensure the connector is firmly installed.
If you use a searchcoil cover, dirt or water can accumulate inside it, and movement of
those materials can cause false signals while sweeping the searchcoil. Searchcoil
covers must be periodically removed and cleaned.
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