False Signals - Fisher M-Scope 1236-X2 Operating Manual

FASLE SIGNALS
A "false signal" occurs when something that shouldn't sounds
like a good target. Your 1236-X2 does an excellent job of ignoring
junk, but it's so sensitive to good targets that it can be fooled by
bad targets with similar electrical characteristics. Large pieces
of trash, for example, or even some kinds of bottle caps and pull
tabs can fool you. Small pieces of trash less than 2 inches from
the search coil will also sound good occasionally.
So what do you do about false signals? Well, 90 percent of them
will sound suspicious to you after you've had some experience,
and you'll just ignore them. They may be very faint or very abrupt
with static. Often when you go back over the same spot, a false
signal will simply disappear. Other false signals may be very loud
and sharp, but most of these will disappear if the coil is speeded
up or raised slightly. Some shallow, large or irregular pieces of
junk, however, will fool the 1236-X2 no matter what you do.
Here's some other sources of false signals and what to do about
them:
1. Detector Interference: Caused by nearby metal
detectors operating at the same (or close)
frequency. SOLUTION: Adjust the FREQUENCY
control to the left or right of zero.
2. Electrical Interference: Caused by radio/TV
stations, power lines, etc. SOLUTIONS: Move further
away, lower the sensitivity, reduce the sweep
speed. Try changing the FREQUENCY control
position. Wrap the search coil cable tightly around
the stem.
3. Highly Mineralized Soil: Usually causes constant
static or good target sounds. SOLUTIONS: Lower the
sensitivity, increase the discrimination. Raise the
search coil until false signals disappear and sweep
at that height.
4. Wet Sand: Same as highly mineralized soil.
5. Elongated Ferrous Objects: If you hear two
beeps very close together and can't find either
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