Fisher Labs F70 User Manual

Metal Detector

Users Manual

OPERA

TING MANUAL

GUIDE TO MET

AL DETECTING

The F70 is a multipurpose metal detector.

It’s most popular uses are coinshooting and relic hunting.

Product Features

• Light weight and well-balanced

• Menu-driven user interface

• Large LCD screen

• Visual indicators of important values such as: Target Identification Target Confidence Target Depth in Pinpoint Mode Ground Mineralization (Dirt indicator)

• Two Search Modes: Discrimination Autotune

• GroundGrab™ touch pad ground balancing

• Waterproof 9 3/4” open-frame concentric elliptical search coil

• Touch pad actuated target pinpointing with variable audio pitch

• Adjustable Arm Rest

• Notch and discrimination controls

• Two retrievable user-programmed memory settings

If you have any questions, or need assistance with your metal detector, Call

915-225-0333 or 1-800-685-505, and ask for Fisher Hobby

echnical

Service.

How Metal Detectors Work

Most hobby metal detectors use VLF Induction Balance technology. Here's how they work. The search coil (also called search head or loop) contains two electrical induction coils which

are like antennas. One coil transmits a rapidly alternating magnetic field, region surrounding the search coil. If metal is present, its electrical conductivity distorts the magnetic field. If iron metal is present, its magnetism also distorts the magnetic field, but in a different way, allowing the metal detector to distinguish between ferrous and nonferrous metals.

The other coil is a receiving antenna which detects changes in the magnetic field caused by the presence of metal. Electronic circuits amplify this weak signal, analyze it to determine the changes which occur as the search coil sweeps over the target, and then convey the information to the user in the form of a visual display or audio tones. Most modern metal detectors perform many of these tasks in software running on an internal microcomputer.

The iron minerals which are present in most soils also distort the magnetic field, obscuring the weak signals of small or deep objects. This can cause the object to go undetected, or to be misidentified when it is detected. Much of the technology that goes into modern metal detectors is devoted to the task of eliminating the unwanted signals from iron minerals in the soil, while not losing the signals from metal objects.

Table Of Contents

Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

Quick-Start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

Mechanicals

Assembly Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7

Mechanicals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

Arm Rest Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

Using Headphones (not included) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

Introduction to the F70

General Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-11

Menu System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

Ground Balancing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-15

Autotune Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

Discrimination Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17-19

Pinpoint Feature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20

LCD Visual Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21-23

Frequency Shifting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

Capabilities & Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25-27

Tips & Techniques

Search Techniques

How to Sweep the Search Coil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28

Pinpointing Targets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28

Estimating Target Size, Depth, & Shape . . . . . . . . . . . . . . . . . . . . . . . . .29

False Signals & Chatter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30

Adjusting Sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32

Tips on Ground Balancing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33

Detecting Activities

Coinshooting

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34

Relic Hunting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34-35

Gold Prospecting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36-37

Cache Hunting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37

Shallow Water Hunting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38

Salt-Water Hunting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38

How Metal Detectors Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39

Warranty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40

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Specifications

Mechanical: 3-piece breakdown aluminum pole system, batteries under elbow,

Armrest adjustment - forward/backward.

Search coil: 9 3/4” open-frame waterproof concentric elliptical search coil. Batteries: 4 AA, alkaline (included). Weight: 2 pounds 15 ounces (1.3kg), with alkaline batteries installed. Operating Principle: VLF induction balance Operating Frequency: nominal 13 kHz, quartz crystal timing reference Basic Sensitivity: 6 x 109root Hertz (detectivity) Lag Coefficient: 78 milliseconds Overload: standard 10” elliptical concentric

Reactive approximately 10,000 micro-cgs Resistive approximately 1,200 micro-cgs

accessory 11” bi-axial

Reactive approximately 30,000 micro-cgs Resistive approximately 3,700 micro-cgs

Resistive Overload: approximately 1,200 micro-cgs units (volume susceptibility)

4,800 micro-cgs units with sensitivity < 30.

Ground Balancing Range:

From ferrite to salt, inclusive

Discrimination Ground Suppression:

combination of second and third order methods

ID Ground Suppression:

third order

Battery Life: Typically 40 hours with high quality alkaline batteries

Estimated 80 hours with nickel oxyhydroxide batteries Estimated 65 hours with lithium iron disulfide batteries

Operating Temp Range:

4 to +122 degrees F (-20 to +50 degrees C)

Operating Humidity Range:

0-90% non-condensing

Detecting Activities (continued)

Gold Prospecting (continued)

Gold prospectors are mostly a friendly bunch, and willing to spend some time showing a beginner how to increase his odds of finding the yellow stuff. Many will invite you to search on their claims (if they have any) once they get to know you. In some gold areas, a lot of the terrain is under claim, so you need to learn how to recognize posted claims and stay off of them unless you have the claim owner's permission. Prospecting clubs such as the GPAA often own claims which are open to their members, and sponsor group outings to good gold areas.

To dig into the ground and pull out a precious piece of yellow metal that you are the first person on earth to see, can be a thrilling experience. If you love being outdoors, have patience, and can stay motivated by the prospect of finding that next nugget, then

gold

recreation where your finds might defray the expense while having fun doing it!

Cache Hunting

A cache (pronounced "cash") is an accumulation of money, jewelry, gold, or other valuables, which someone has hidden. When people bury a cache, they usually put it in a strongbox or in a jar. To search for a cache, you first need a reason to believe the cache may exist. This means doing research. Some caches have been the subject of many stories you can read about in print, but you need to be able to sort fact from fiction. If you can get copies of old newspaper stories about the circumstances surrounding the hiding of the cache, you may find discrepancies which help you to judge the reliability of the information available. Often the best information on an old cache is to be learned from old timers who live in the area where the cache is thought to be. In the case of newer caches, often the only information is what can be obtained from family and acquaintances of the person who is believed to have hidden the cache.

The ownership of a cache is not always clear. Sometimes it belongs to the person or heirs of the person who hid it, sometimes it belongs to the owner of the property on which it is located, and sometimes it belongs to the person who finds it -- or some combination of the above. If the contents of the cache were stolen, this fact can also complicate the question of ownership. Find out what laws apply to the cache in question, and always make sure that the issue of ownership is resolved prior to recovering a cache.

Compared to a coin, a cache is usually large and deep. Searching in recommended. However, for a really deep cache, it may be advantageous to search in PINPOINT, by keeping the button depressed, frequently releasing and re-depressing the button momentarily to maximize sensitivity

Quick Start

Use your F70 right out of the box

1. Assemble the detector (see instructions beginning page 4).

2. Install four AA

alkaline batteries. All positive (button-end) terminals point up.

Batteries are included with the detector.

3. Turn the knob, located under the armrest, fully clockwise. This turns the machine on and sets audio volume to maximum.

4. When first turned on, the

F70 starts out in the Discrimination mode, with presets at: Discrimination Level = 15 (iron eliminated) in both program-1 and -2. Speed = dE Sensitivity = 60 Threshold = 0 Number of Tones = 3

Sweep the search coil from side to side, parallel to the ground. Keep the search coil moving over the ground. If you stop moving the search coil, the sound will also stop. Probable target type will be indicated at the top of the LCD screen.

5. If the search coil is not in motion and not close to metal, the detector should be silent.

6. If you experience false signals from electrical interference, from the soil itself, or from lots of trash metal, press MENU button until:

Sensitivity is highlighted. Press “-” as needed Reduce the sensitivity setting until the false signals go away. After 7 seconds, the machine will exit the menu, unless you exit by pressing MENU first.

7. Toss a coin on the ground and sweep back and forth over it a few times to get a feel for how the machine responds.

8. You are now ready to search.

9. Press-and-Hold the PINPOINT button to pinpoint the exact location of targets, making them easier to unearth.

When Pinpoint is held ....

The search coil need not be in motion to detect an object. The 2-digit numeric display indicates approximate target depth, in inches.

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Assembly

1. Remove all components from box.

2. Attach

search coil to lower stem by lining

up the holes.

Notice that the lower stem is supplied with

no rubber washers. Push coil bolt

through hole and tighten gently with coil knob.

You will tighten up the coil knob later.

3. Insert middle stem into S-rod (S-rod holds detector body).

Turn

top locking collar

counter-clockwise to open up. Push in

pin on middle stem. Slide middle stem into S-rod. Click pin into hole and tighten top locking collar firmly clockwise.

4. Push

lower stem into middle stem as

follows:

Turn lower locking collar counterclockwise to open up. If plastic insert tab interferes, push it down, or turn tube upside down. Push in pin to allow rod to slide in. Slide lower stem in. Then click pin into any hole.

5. Remove

velcro strips.

6. Wrap

cable around stem as follows: Leave some slack in cable at base of lower stem. Secure cable at base of lower stem with velcro strip. Wrap cable loosely around entire stem up to bent part of upper rod.

You will re-wrap the cable later after sizing the rods to your height.

7. Push cable into connector on back of housing.

Do not twist the cable or plug.

Turn knurled cap nut only. Do not cross thread.

Coil Knob

Coil Bolt

Top Locking Collar

Lower Locking Collar

Biaxial Search Coil

Detecting Activities (continued)

Relic Hunting (continued)

Most relic hunting locations are in fields, forested areas and vacant lots where digging holes will not damage turf grass, so having a detector with good depth sensitivity is important. Some places are so littered with iron that it is necessary to discriminate out iron in order to be able to search, even though you may miss some potentially valuable artifacts.

Before you go relic hunting, obtain permission from the property owner. If you intend to hunt on public land, check first with the administrator to make sure it's not illegal. Certain kinds of sites, on both public and private land, are protected by law from relic hunting. If there is a metal detecting club in your area, some of the members will probably know what the laws are in that area and which sites are off limits.

Relic hunting is most rewarding if you have an avid interest in history. In many cases, the value of a relic is not the object itself, but the story it's a part of -- what historians call provenance. A few pieces of rusty metal can tell the story of life in a specific place, or that of a specific family or person from hundreds of years ago. They can capture our imagination and help to give context to our lives today.

The value and context of a find can be readily lost without proper documentation and storage. Add finds to your collection with care. Take the trouble to understand the site you are searching and keep track of where you find things. Describe exactly how and where items were found. Consider including a sketch of the site with your finds. Organization techniques might include storing together all finds from the same site. Alternatively, if you have an interest in specific items, like buttons, make a button collection, and within that collection, document the circumstances surrounding each button found. If your finds are mixed together, without categorization or documentation, their context will be lost.

The ground balancing and DIRT bar graph features of the F70 can be used to map the soils of a site. In this way you might determine which areas have been dug, backfilled, or subjected to fire. This information in turn helps to reveal the history of the site.

To find promising sites to hunt, conduct research at your local library, look for clues in old newspapers, and seek information on the Internet. Where did buildings used to be? Which have since been torn down? Where did people gather for public events like dances and county fairs? Where did train and stage lines run? Where were the swimming holes? In almost every town there is a historical society and museum of local history. Most museums are grateful for anything they can put on display, and when you dig something you cannot identify, the curator can often identify it for you. If you work closely with the local historical society or museum, landowners will be more willing to grant you permission to search their property

Some of the most promising sites for relic hunting are places being cleared for development. After the site is built on, whatever is in the ground will become inaccessible. can often be persuaded that the site should be searched immediately while it is still searchable.

8. Tighten knurled cap nut by hand to secure cable connection to housing.

Do not twist the cable or plug.

IT IS VERY IMPORTANT THAT THE NUT ROTATE FREELY AT FIRST (do not cross thread), After a free-rotation start to threading, insure that the NUT IS TIGHTENED FIRMLY. One thread will still be visible when the nut is tightened securely.

9. Adjust to your height: Hold detector, standing up, with your arm in the

armrest.

Place search coil flat on the ground with back edge of coil 6” in front of your toes. Click pin on lower stem into nearest hole. Firmly tighten

lower locking collar to secure lower stem.

10. Attach cable to top of of the middle stem with the other

velcro strip.

11. Tighten up coil knob to keep search coil from flopping.

12.Insert batteries.

4 batteries are all installed the same way —

positive terminals pointed upward.

After establishing a comfortable length, firmly tighten the locking collars on the rods to prevent the tubes from rattling. Rotate the collars a full 270° to engage and lock in place. If you are unable to rotate a full 270°, use gloves for a better grip.

If the search coil appears crooked with respect to the pole, loosen both locking collars and readjust. Hold each of the stem in the counterclockwise position as you tighten.

Assembly (continued)

OPERATING MANUAL &GUIDE TO METAL DETECTING

Search Techniques (continued)

TIPS ON GROUND BALANCING

When the F70 first turns on, the ground balance setting is preset to 90. This will give a in the Discrimination mode, you will probably not have to balance to the ground. If you switch to Autotune mode, ground balancing will probably be necessary.

You must find a spot of ground which is free of metal to accurately balance to the ground. Before you attempt to Ground Balance, sweep back and forth to see if any metal target is present. Locate what seems to be a clear area and then Ground Balance using the GroundGrab procedure. After you have ground balanced, sweep back and forth to see if there is little or no audible response to the soil. This is best done either in Autotune mode, or in Discrimination mode with Disc Level set to zero. Alternatively, use Pinpoint to check the spot. If there is little or no response, ground balancing was successful. If there is still substantial response, there may have been metal present where you attempted to ground balance, so find another promising spot and try again. If you cannot find a spot to successfully ground balance, it is time to give up.

In most areas, once you have ground balanced, the ground balance setting will remain satisfactory for a long time. However, if the soil has been disturbed by digging or the addition of fill dirt, or if you are in a geologically complex setting such as is commonly encountered in gold prospecting areas, you may have to frequently perform the ground balancing procedure to accommodate changing soil conditions.

When you ground balance, the numerical Ground Phase will momentarily appear on the LCD screen. In general, sandy or gravelly soils will tend to read in the 75-95 range, light colored loams and clays will tend to read in the 50-80 range, and red clays will tend to read in the 35- 55 range. To express it in other terms, the more highly weathered, oxidized, or finely grained the soil is, the lower the numeric reading will tend to be.

The DIRT bar graph indicates how much iron mineralization is present. For it to work, the search coil must remain in motion. The most accurate readings will be achieved by the coil as you do when ground balancing. The higher the mineralization, the greater the necessity to ground balance the detector for the best depth performance.

If you are searching for relics, you can make a map of the soil of the site. Make a grid of the site. Then collect data. Ground Balance to document mineral the DIRT bar graph. Then plot the data on the site map and draw isolines. In this way you may be able to locate areas which have been dug, backfilled, or subjected to fire. This information in turn helps to reveal the history of the site.

Mechanicals

BATTERIES

The F70 requires four AAbatteries. These non-rechargeable chemistries may be used: Alkaline, Nickel Oxy-Hydroxide (Panasonic Oxyride or Duracel PowerPix), and lithium iron disulfide (Energizer L91). Nickel metal hydride and nickel-cadmium rechargeable chemistries may also be used.

Zinc-carbon and so-called “heavy duty” batteries may not work, especially in cold weather

Do not use these batteries. Expect 40 hours of service in the field with one set of alkaline batteries.

Rechargeable batteries will usually deliver over 25 hours of service without recharging, but when they start running low, they die suddenly with little warning.

Always install batteries which are of the same type and the same state of charge. Otherwise battery life will be determined by the weakest battery, because the good batteries cannot deliver their power with a dead battery blocking the current.

All 4 batteries are installed with the positive terminals facing upward. The LCD screen shows battery condition on the right.

ARM REST

The arm rest is adjustable up and down the pole.

If you notice unwanted movement while swinging the detector, check the tightness of the locking collars. The locking collars must be rotated a full 270° to reach the locking position.

HEADPHONES (not included)

The F70 is equipped with a standard 1/4-inch stereo headphone jack at the rear of the unit, located under the elbow as you hold the detector for use. Any headphone with a 1/4” stereo plug should work; headphones with a mono plug will not work. Afew electronic head phones may not be compatible. This device is to be used with interconnecting cables/headphones shorter than three meters.

Using headphones (not supplied) improves battery life, and prevents the sounds from annoying bystanders. It also allows you to hear subtle changes in the sound more clearly, particularly if searching in a noisy location. 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.

Introduction to the Fisher F70

HIGH PERFORMANCE The F70 is a multi-purpose high-performance computerized metal

detector. It has the high sensitivity and ground balancing control needed for even the most challenging soil conditions, the discrimination responsiveness needed for serious relic hunting under difficult conditions, and visual target ID considered essential in searching for coins. The

F70 operates at 13 kHz for good sensitivity to gold nuggets and

jewelry as well as to coins. The

F70 comes with a 9 3/4”-inch open-frame waterproof

concentric elliptical search coil for broad sweep yet narrow target pinpointing.

USER COMFORT The F70 is among the lightest and best balanced of all high-performance

metal detectors, so you can hold and swing it almost effortlessly. The grip is durable highfriction 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.

LOW OPERATING COST The F70 is powered by four AAalkaline batteries, which will

typically last for more than 40 hours of use before needing replacement.

engineer on the

F70 design team was John Gardiner. John’s previous Fisher design credits include the F75, F4, and F2. Assisting John Gardiner were John Griffin, Dave Johnson, Mark Krieger, and Gerhard Staiger.

MECHANICAL ENGINEERING

While the F70 is robustly engineered for outdoor use, it is not indestructible and it is not waterproof.

RESET function

The F70’s microprocessor will save all settings which you input, even after the power is turned of

If you wish to reset the settings to the factory preset, follow this process:

urn detector of

2. Press-and-hold both the GROUNDGRAB and MENU buttons.

3. Turn the detector on, while you are still pressing the buttons.

4. Detector displays “88”.

5. Release the buttons.

6. The detector is reset, and operating in program-1.

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Controls

ON-OFF & VOLUME Knob

(Under the elbow)

This knob turns the machine on or off, and controls speaker volume and headphone volume.

Knob position has no effect on detector’s sensitivity or susceptibility to noise from electrical interference

The F70 has six controls on the front panel.

Frequency

Shift

On/Off &

Volume

Pin-Point

Control

Minus

Programming

Plus

Programming

Ground

Balance

Activation

Search Techniques (continued)

NUISANCE BURIED OBJECTS

In some areas there is a lot of metallic trash which produces weak signals. These could include deeply buried objects, little bits and pieces of rusty iron and corroded foil. These items can be detected, but are difficult to pinpoint due to their depth and small size. When you dig and find nothing, it may seem like the machine is beeping at nothing even though there is actually something there. The best solution is usually to reduce sensitivity.

If searching a very trashy area and unwanted signals are a problem, search with the search coil 2 inches (5cm) away from the ground. Trash objects very close to the search coil will sometimes not be completely eliminated, even when the discrimination setting should have eliminated the target.

Metal detectors are designed to see one metal object at a time. Where there are two iron objects near each other, the detector can be fooled into thinking that the gap between them is nonferrous metal. This is a common condition where a wooden building has burned or been torn down, and the site is littered with nails. Asignal from a nonferrous metal object such as a coin will usually be repeatable, whereas a false shaped iron objects will seem to wander around and even to vanish. Experienced detectorists call these signals are almost always trash.

GROUND MINERALS

Conductive mineral salts usually produce broad signals which will not be mistaken for a metallic object. Common causes are concentrations of mineral fertilizer, spots where evaporation has concentrated naturally occurring mineral salts, residue from de-icing salts, and urine from livestock. Unless dry, “cow pies” can sound off like they are metal. Ocean beaches have salt water—this subject is discussed elsewhere in the manual.

In spots where there has been intense fire, such as a campfire site or where a stump was burned during land clearing, the soil minerals may be altered by oxidation so that their ground balance setting is lower than that of the surrounding soil. In such cases, search slowly.

In some areas, electrically conductive industrial minerals such as fuel coke, slag, clinkers (left over from burning mineral fuels), or charcoal have been dumped or used as landfill. Individual lumps of these materials can usually be quieted by reducing sensitivity and searching with a discrimination level of at least 25. However, where the ground consists primarily of such materials, you may not be able to search quietly crisp and repeatable.

Electrically conductive natural minerals such as graphite, graphitic slate, or sulfide ore minerals are rarely encountered except when gold prospecting. When gold prospecting, you need to be able to hear everything, and you can expect to dig conductive minerals that turn out not to be gold. In a given locality you may learn to recognize what type of rocks these minerals are found in, and to ignore them if people in the area say that gold is not found in rocks of that type.

MENU button

Push the MENU button to:

1. Step through the menu selections on the display. With each push of the button, the next menu selection will be highlighted. The - or + buttons then allows you to change values for the highlighted selection.

2. Recall the last setting which you adjusted. After you have adjusted a setting, the

■

indicator will remain highlighted next to this menu selection. One push of the MENU button will recall that selection and display the stored value.

This recall function is useful for a value you want to adjust frequently.

+ and - buttons

Press + or - buttons to change the settings (or value) of the highlighted menu selection you have chosen.

PINPOINT button

While the button is depressed, metal objects are temporarily detected without the need for search coil motion. This aids in pinpointing the exact location of objects which were found while searching in the Discrimination or Autotone modes.

GROUND GRAB

Press-and-hold the button to activate automatic ground balancing. The internal computer measures the magnetic properties of the soil in order to cancel interference from naturallyoccurring minerals in the ground. After the detector measures the soil in this manner, the detector then uses this information to control operation in both the Discrimination and Autotune search modes. GROUND GRAB can be used at any time during operation. The coil must be pumped up and down over the ground while holding the button. See section on ground balancing.

Pressing this button changes the detector’s operating frequency. Use this feature if you suspect that the detector is behaving erratically due to the presence of electrical interference from some other electronic device. Press and release one time to change to another frequency

. Default value is 4.

There are a total of 7 frequencies.

Note that after changing frequencies, you need to ground balance the detector again, as changing operating frequencies will move the ground balance point.

Controls (continued)Search Techniques (continued)

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The Menu System

The entire menu is printed on the LCD display. There are two search modes, Discrimination and

Autotune.

To select the

Autotune mode:

1. Press MENU until the DISC LEVEL line of the menu system is highlighted.

2. Press “-“ until the display reads

“At”.

To return to

Discrimination mode:

1. Press MENU until the DISC LEVEL line of the menu system is highlighted.

2. Press “+” until a value other than

“At” is

displayed. Each search mode has several adjustable function settings:

AUTOTUNE: Speed, Sensitivity, Threshold. DISCRIMINATION: Discrimination Level, Speed, Sensitivity, Threshold, # of Tones, and Notch.

You can establish two different sets of program settings

for recall, using the PROGRAM selection.

- The number next to “PROGRAM” indicates

which program is active.

- To change from one program to another, press

“+” or “-“ while “PROGRAM” is highlighted.

- Press “+” to choose program-2.

- Press “-“ to choose program-1.

One convenient application for PROGRAM is to

change easily between the Autotone and

Discrimination modes. To do this, program the two modes as follows:

1. Go to DISC LEVEL. Select

“At” with “-“ button.

2. Then press MENU until “PROGRAM” is highlighted. Press “+” or “-“ to change the program number. Then press MENU to move down to DISC LEVEL and press “+” or “-“ to choose a DISC LEVEL setting other than

“At”.

Then toggle between the two modes, or programs, as follows:

1. Press MENU until PROGRAM is highlighted.

2. While “PROGRAM” is highlighted, press “+” or “-“ to change between modes. If you are programming the detector after pressing MENU and do not press a button after 7

seconds, the detector will exit the menu system automatically

, and resume normal operation.

Any value currently displayed will be saved into memory. If you press the MENU button while the machine is in normal operation, the user interface will

return to the last menu selection you had adjusted. The last menu selection is indicated while the menu system is inactive with a highlighted

■

symbol.

Search Techniques (continued)

ESTIMATING TARGET SIZE, DEPTH, AND SHAPE

When Pinpoint is activated, the LCD displays estimated depth. The estimate is based on the presumption that it is a coin-sized target.

But what if it is not a coin-sized target? The most common example is that of an aluminum can. Flattened aluminum cans are usually identified as zinc, pennies or as dimes. Their large size will produce a strong signal, tricking the microcomputer into thinking that it is a shallow coin.

The following explains techniques for differentiating buried aluminum cans from coins. Sweep back and forth to get a feel for the target, keeping the search coil close to the ground. Now, continue to sweep back and forth as you slowly raise the search coil higher and higher. If the response diminishes quickly and never gets very broad, the target is probably a coin. If the response diminishes slowly as you lift the search coil, and you get a broad response, the target is probably an aluminum can. If you practice this by laying a coin and a flattened aluminum can on the ground, you will quickly understand how to differentiate the two and you will probably never have to dig another aluminum can again. And, you will know whether it was deep or shallow. This technique works well in the Autotune mode, and to a lesser extent in Discrimination mode.

Objects which are ring-shaped, or flat and round like coins, tend to give a narrower, crisper response than objects of similar size with irregular shapes. The easiest way to demonstrate this is with an aluminum screwcap from a soda bottle. In its normal shape, it occupies a volume, and gives a somewhat broader response than that of a coin. But if you flatten it, the response will be crisper and more like that of a coin. Again, these differences are most readily noticed in the Autotune mode.

Long skinny iron or steel objects such as nails usually produce a double response when scanned lengthwise, and a weaker single response when scanned crossways. This is most noticeable in the Autotune mode. However, a coin lying on its edge can produce a similar response, so rely on both the target ID as well as kinds of objects. Objects within 2 inches (5cm) of the search coil will often produce multiple responses as you sweep across them, because the response field close to the search coil is irregular.

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Fisher Labs F70 User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual