Manual

Comprehensive Operating Manual & Guide to Metal Detecting
Comprehensive Operating Manual & Guide to Metal Detecting
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F75
F75
Introduction to the Fisher F75
HIGH PERFORMANCE The F75 is a multi-purpose high-performance computerized metal
detector. It has the high sensitivity and ground balancing control needed for professional
gold prospecting, the discrimination responsiveness needed for serious relic hunting
under difficult conditions, and visual target ID considered essential in searching for coins.
The
F75 operates at 13 kHz for good sensitivity to gold nuggets and jewelry as well as to
coins. The
F75 comes with an 11-inch elliptical Bi-Axial searchcoil for maximum
detection depth in mineralized soils.
USER COMFORT The F75 is among the lightest and best balanced of all high-performance
metal detectors, so you can hold and swing it almost effortlessly. The arm rest position is
adjustable to fit your arm. The grip is durable high-friction foam elastomer, comfortable in
any kind of weather. The controls are conveniently located and easy to learn how to use.
Locking collars on the tubes eliminate rattling.
EASY-TO-USE & INFORMATIVE INTERFACE The entire menu is always visible on the
LCD display. The LCD display indicates the electrical signature (target I.D.) of the
detected metal object. The display provides continuous information on battery condition
and on ground mineralization, which affects detection depth. Help messages are
automatically displayed on the bottom of the display when necessary.
LOW OPERATING COST The F75 is powered by four AA alkaline batteries, which will
typically last for more than 40 hours of use before needing replacement.
DESIGNED BY MANY OF THE INDUSTRY’S MOST TALENTED ENGINEERS
The lead engineers on the F75 design team were John Gardiner and David Johnson.
David Johnson’s previous Fisher design credits include the CZ-platform, the Gold Bug-
series, most of the 1200-series, Impulse Underwater Detector, CZ-20 Underwater
Detector, FX3 magnetometer, the Gemini 2-box locator, the XLT-16 Acoustical Leak
Detector, and the XLG-80 Ultrasonic Leak Detector. John and David were supported by
fellow electrical engineers Jorge Corral, and Mark Krieger. The mechanical design was a
collaboration among David Johnson, Brad Fulghum, John Griffin, and Tom Walsh.
MECHANICAL ENGINEERING
While the F75 is robustly engineered for outdoor use, it is not indestructible and it is not
waterproof.
RESET function
The F75’s microprocessor saves all settings which you input, even after the power is
turned off.
If you wish to reset the settings to the factory preset, follow this process:
1. Turn detector off.
2. Press-and-hold the red MENU button and
push-forward-and-hold the TOGGLE SWITCH.
3. Turn the detector on, while you are still holding the controls.
4. Release the MENU button and TOGGLE SWITCH.
5. See the F symbol. When the F disappears, the detector is reset.
Search Techniques (continued)
HOT ROCKS
A hot rock is a rock which causes the metal detector to sound off because the rock contains
iron minerals. They come in two basic types.
Negative hot rocks (also called cold rocks) are usually magnetite or contain magnetite,
and give a negative response because their ground balance value is a higher number
than the soil they are found in. They tend to be dark in color, usually black, and usually
heavy. In some cases they will have rust stains. They are usually attracted to a magnet,
and for this reason gold prospectors always carry a magnet—the ultimate
ferrous/nonferrous discriminator. In Motion All Metal mode, negative hot rocks produce a
boing sound rather than the zip sound of a metallic target; recognize the difference and
you will learn to ignore them.
Positive hot rocks are iron-bearing rocks which have been oxidized by natural weathering
processes so that their Ground Balance number is a number lower than the soil they are
found in. They are often small, right on the surface, sound just like a gold nugget, and
are common in many gold prospecting areas. They are usually, but not always, drawn to
a magnet. They are most often reddish in color but are often black, brown, or yellow. On
relic hunting sites, red clay bricks and rocks which have lined a fireplace or a campfire
will often be
hot rocks. The discriminator will usually eliminate them without difficulty if
widely scattered, but if there is a large concentration of them, the discriminator may not
quiet them all. In that case, you can revert to the rule of thumb -- “don’t dig non-
repeatable signals”.
Using the sensitivity control
When the F75 is first turned on, the Sensitivity is at a medium setting appropriate for most
coinshooting. For relic hunting or gold prospecting, higher Sensitivity settings are usually
preferred.
In the event of detection of electrical interference from electrical power lines, electrical or
electronic appliances, or another metal detector, it is usually necessary to reduce the
Sensitivity setting to achieve quiet operation. Alternatively, use the Frequency Shift feature
described earlier in this manual.
If, while searching, you are constantly getting signals from which you cannot recover metal
targets, you may be detecting small or deep targets which are not recoverable using the
methods at hand. So, you may do better if you reduce the Sensitivity setting.
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