Fisher F4 Hobby Metal Detector

5-Year Limited Warranty

The F4 metal detector is warranted against defects in materials and workmanship under normal use for five years from the date of purchase to the original owner. Damage due to neglect, accidental damage, or misuse of this product is not covered under this warranty. Decisions regarding abuse or misuse of the detector are made solely at the discretion of the manufacturer. Proof of Purchase is required to make a claim under this warranty. Liability under this Warranty is limited to replacing or repairing, at Fisher Labs' option, the metal detector returned, shipping cost prepaid. Shipping cost to Fisher Labs is the responsibility of the consumer. To return your detector for service, please first contact Fisher Labs for a Return Authorization (RA) Number. Reference the RA number on your package and return the detector within 15 days of calling to: Fisher Labs, 1465-H Henry Brennan Dr., El Paso, TX 79936. Phone: 915-225-0333 ext. 118. Warranty coverage does not include the cost of transporting the detector back to an owner located outside of the United States of America.

Copyright © 2007. All rights reserved, including the right to reproduce this book, or parts thereof, in any form. Fisher® is a registered trademark of Fisher Research Labs.

Website: www.fisherlab.com

Product Overview

An illustration of the Fisher F4 Hobby Metal Detector, showcasing its main components: a circular search coil at the bottom, a shaft with an adjustable length, a control box with a digital display and buttons, an armrest for user comfort, and a handle. A prominent diagonal banner across the detector reads "USE ALKALINE Batteries ONLY".

Setting Up

No tools are required for assembly.

1. Insert the lower stem (plastic tube) into the middle stem.
2. Position the lower stem with the silver button toward the back. Using the provided bolt and wing nut, attach the search coil to the lower stem.
3. Press the button on the upper stem and slide the lower stem assembly into the upper stem. Adjust the stem to a length that allows you to maintain a comfortable upright posture, with your arm relaxed at your side, and the search coil parallel to the ground in front of you.
4. Wind the cable securely around the stem.
5. Insert the plug into the matching connector on the right underside of the detector body. Ensure the key-way and pins align correctly.
6. After adjusting the stem length to your height, tighten the two locking collars to stabilize the stems.

Arm Rest Adjustment: If you wish to change the position of the arm rest, remove the screw and move the arm rest to one of the alternate hole locations.

Caution: Do not force the plug in, as excess force can cause damage. To disconnect the cable, pull on the plug, not the cable.

Batteries

The F4 is supplied with two 9-Volt batteries. These batteries may have been inserted backward in the compartment for storage. Please remove them, turn them around, and install them correctly. Use ALKALINE batteries only. Do not mix old and new batteries.

To install the batteries:

1. Remove the battery cover by disengaging the clip at the back. Pull straight back; do not hinge the door upward.
2. Align the polarity of the batteries correctly, with the positive (+) terminal toward the coil plug connection, as indicated by the + and - indicators on the housing.
3. Insert two 9-Volt ALKALINE batteries, with the contacts pointed inward, and press down on the back of the batteries to snap them into place. Some battery brands may require moderate force to clear the retaining tabs.
4. Replace the battery door.

Most metal detector problems are due to improperly installed batteries or the use of non-alkaline or discharged batteries. If the detector does not turn on, please check the batteries.

Headphone Jack

Using headphones (not supplied) with your metal detector makes it easier to identify subtle changes in the threshold levels for better detection results, and also reduces drain on the batteries. Any stereo headphone with a 1/4" jack will work.

Control Panel

The operating controls are as follows:

Sensitivity Adjustment

The Sensitivity controls (+ and -) change the detector's sensitivity; higher settings enable detection of deeper targets. At power-up, the detector is pre-set to 75% of maximum sensitivity. At minimum, sensitivity is 35% of maximum. With each press of the + or - touch pads, the sensitivity level is displayed on the bar graph on the left of the display. The detector will beep twice upon reaching the minimum or maximum sensitivity setting.

While higher sensitivity levels enable detection of deeper targets, operating at high sensitivity makes the detector more susceptible to electromagnetic interference (EMI). High sensitivity settings can also lead to false signals in difficult ground conditions. Use lower sensitivity settings to suppress interference or false signals from soil minerals when necessary. If the detector "chatters", reduce sensitivity.

Electromagnetic Interference (EMI)

Use the Sensitivity Control to eliminate Electromagnetic Interference (EMI). The F4 metal detector is highly sensitive; its search coil creates its own magnetic field and acts like an antenna. If your detector beeps erratically when the search coil is motionless, it is likely detecting another electromagnetic field. Common sources of EMI include electric power lines, motors, household appliances (computers, microwave ovens), and dimmer switches. Other metal detectors can also produce EMI; maintain at least 20 feet separation when detecting with others.

To manage chatter from electrical interference:

1. Reduce the SENSITIVITY until the chatter stops.
2. Try sweeping the coil over the ground. If the F4 chatters while held still or in the air, it may be quieter when sweeping over the ground.
3. Operate in AUTOTUNE mode, which tolerates interference better, even at high sensitivity.

Severe Ground Conditions

The Sensitivity Control can also reduce false detection signals caused by severe ground conditions. While the detector has circuitry to eliminate signals from most naturally occurring ground minerals, 100% of all ground conditions cannot be anticipated. Highly magnetic soils or highly saline content soils can cause false signals. If the detector emits false, non-repeatable signals, REDUCE THE SENSITIVITY.

Auto Tune (All Metal)

Press this pad, and "ALL METAL" appears on the display. This is a ground-balanced, all-metals motion search mode offering maximum sensitivity under most ground conditions. The search coil must be in motion to detect metal. It emits a single monotone sound. Discrimination or target identification is not possible in this mode.

Use the Sensitivity or Threshold controls to change sensitivity or background hum. Maximum sensitivity to buried metal objects is achieved with a slightly audible background hum.

To achieve an audible background hum:

1. Press the AUTO TUNE pad.
2. Press Sensitivity + or - pads until you reach a desired setting (highest "quiet" setting or a faint background hum).
3. Press Threshold + or - pad until you reach a comfortable volume level.

The Sensitivity control acts as a course adjustment, while the Threshold control acts as a fine adjustment.

The AUTO TUNE mode must be ground-balanced to eliminate interfering signals from soil minerals. Refer to the ground balancing section for procedure.

Discrimination (Threshold) + and –

The function of these controls depends on the operating mode. In AUTO TUNE mode, + and - change the threshold sensitivity. This control acts as a fine adjustment for sensitivity level and background hum. Pressing + can cause the detector to emit a sound or hum when no metal is present. Some users prefer operating with an audible hum for detecting faint signals from deeply buried or very small objects.

In PINPOINT mode, these pads have no function.

Disc

This control invokes motion target identification search modes. Successive presses of the DISC pad toggle between All-Metal Discrimination mode (detects all metal targets) and Discrimination mode (selectively eliminates target categories). When the detector powers up, it enters ALL-METAL DISCRIMINATION mode. Press DISC to enter discrimination mode. Press DISCRIMINATION + to eliminate more targets. Press DISCRIMINATION - to reverse elimination (illuminated "R"s disappear).

Each press of the + or - pads will cause an "R" to appear or disappear on the display. When an "R" appears, the corresponding target category is eliminated from detection. No audible tone or target arrow will appear for objects in categories with an "R" illuminated. Up to seven "R"s can be displayed, eliminating targets up to the Zinc-1¢ category. The four right-most target categories cannot be eliminated.

Notch

This control allows selective inclusion or exclusion of target categories. It can be invoked from any search mode. After selecting categories to notch-in or notch-out, the detector returns to motion discrimination mode. Notching functions manually or automatically.

Manual Notch: If no target arrows are visible, pressing the NOTCH pad displays an "R" under all currently eliminated target categories, and the "L" under Iron-1 flashes. Use the Discrimination + or - pads to move the flashing "L". Pressing NOTCH a second time changes the state of the "R" under the flashing "L" (illuminated "R" disappears, un-illuminated "R" becomes illuminated, eliminating the category). Practice by using the NOTCH pad with the Discrimination + and - pads.

Automatic Notch: If a target has just been detected and a target arrow is visible, pressing NOTCH immediately illuminates a flashing "L" under that category. Press NOTCH a second time to eliminate that target category. This is a convenient way to quickly eliminate the most recently detected target from future detection.

Pinpoint

This is a static search and static pinpointing mode; no coil motion over the target is required. It is most effective for pinpointing the exact location of small buried objects. Detection sensitivity is controlled by the SENSITIVITY + or - pads. Discrimination (Threshold) + / - has no function. Reduced sensitivity and a smaller search field can be achieved by pressing the PINPOINT pad while an object is in the coil's detection field. This mode offers the greatest sensitivity to large, deeply-buried objects. If using PINPOINT as a continuous search mode, the detector must be ground-balanced first.

4-Tone Audio System

While the LCD display is accurate, the user may not always have it in view. The 4-tone audio system provides audio feedback to alert the user to the nature of buried objects. This system functions only in motion modes (DISCRIMINATION mode). In PINPOINT or AUTOTUNE modes, a monotone sound is emitted.

The detector can sound four different tones:

• Low Tone: Ferrous objects (iron, steel) and smallest gold objects.
• Low-Mid Tone: Pull-tabs, nickels, and smaller gold objects.
• Medium Tone: Newer pennies (post-1982), larger gold objects, zinc, and small brass objects. Many recent vintage non-U.S. currencies also produce medium tones.
• High Tone: Silver and copper coins, larger brass objects, and older pennies (pre-1982). Quarters, dimes, and other precious coins fall into this category.

An illustration shows examples of objects corresponding to each tone category.

Depth and Target Display

The Liquid Crystal Display (LCD) shows the PROBABLE identification of the targeted metal and its PROBABLE depth in inches. An arrow illuminates under the target category where an object is best classified and stays illuminated until another target is identified. A repeating, unchanging target identification indicates a located target. Inconsistent readings upon repeated passes suggest trash, oxidized metal, or a target too deep to classify accurately. Practice helps in unearthing only repeatable signals.

Segment identifications are highly accurate for described objects. However, registering in a category for an unknown object means detecting a metallic object with the same metallic signature. Greater distance between the target and the coil reduces identification accuracy.

Target Categories:

• Gold Targets: Register on the left side of the LCD scale. Smaller gold objects register further left. Gold flakes register under Iron-1. Small gold items register under Iron or 5¢/PT. Medium-sized gold items register under PT or S-cap. Large gold items register under S-cap or Zinc.
• Silver Targets: Normally register on the right side of the scale, under 10¢, 25¢, 50¢, or $1, depending on size. Larger objects register further right.
• Iron: Ferrous objects register on the far-left side. 1 or 2 indicates relative size. Small nails illuminate Iron-1; large structural ferrous objects illuminate Iron-2. These could be scrap or valuable iron relics.
• 5¢/PT: Nickels and most newer pull-tabs register here.
• PT (pull-tabs): Pull-tabs from older beverage cans and some newer ones register here. Many gold rings also register here.
• SC (Screw Caps): Screw caps from glass bottles register here. Large gold rings (like class rings) could also register here. Some non-U.S. coins register here.
• ZINC/1¢: Newer pennies (post-1982) register here. Many non-U.S. coins of recent vintage also register here.

Depth Indicator:

The Depth Indicator is calibrated for coin-sized objects and shows target depth in inches. Large or irregularly-shaped objects yield less reliable depth readings. The indicator lights up and stays illuminated until another object is scanned. Repeated indication at the same depth level suggests an accurate target. Varying indications may mean multiple targets or trash. Practice helps distinguish accurate readings from erratic ones.

2-Digit Depth (Pinpoint Mode):

In PINPOINT mode, the 2-digit number indicates estimated target depth in inches, calibrated for coin-sized objects. Larger/smaller objects yield relative depth readings. Accuracy is best when the detector is ground-balanced and the threshold is set for no audible hum or a very faint hum. Depth indication is less accurate if "de-sensitized" or if the audible tone is too high in PINPOINT mode.

2 Digit Target Indicator:

In DISC or NOTCH mode, the 2-digit target indicator provides a specific target value to help identify buried targets more accurately. Target values can vary based on object angle and distance from the coil. Refer to the table below for common equivalents.

Target Readout Table:

Search Techniques

Target Verification

After detecting a target:

1. Walk around the target in a circle.
2. While circling, continue sweeping the searchcoil across the target.
3. Sweep once every 30° or 40° of the circle.

If the tone does not change and the target ID value is consistent as you circle, you can be highly confident of the target's identification. If the tone or target ID changes, you may have multiple targets or an irregularly shaped object. If the tone disappears at different angles, the target may be trash or a low-value metal.

Coil Movement: When swinging the coil, keep it level with the ground about 1/2 inch from the surface. Never swing the coil like a pendulum.

If you are new to the hobby, dig all targets. With practice, you will learn to identify audible and visual target feedback with certain metal objects.

Pinpointing Process in Motion Modes:

1. Sweep over the target in a narrow side-to-side pattern.
2. Take a visual note of the spot on the ground where the "beep" occurs.
3. Step 90° to the side of the target.
4. Sweep the coil over the same area at 90° to the first sweep pattern.
5. This pinpoints the target location with an "X".

Target Pinpointing (No-motion PINPOINT Mode)

After identifying a target with a motion mode, press the PINPOINT pad to find its exact location. This technique can yield more information about the target's shape and size and facilitate excavation.

Pinpoint (in no-motion mode) steps:

1. Position the searchcoil just barely off the ground, to the side of the target.
2. Press the PINPOINT pad and raise the searchcoil about 2 inches. Lifting the searchcoil away from the ground makes the ground signal go negative, silencing the machine.
3. Slowly move the searchcoil across the target. The target is located directly under where the sound is loudest.

Narrow It Down:

1. To narrow the response, position the center of the searchcoil near the center of the response pattern, but not directly over it.
2. Press the PINPOINT pad again.
3. Repeat this narrowing procedure to further narrow the field of detection.

Note: Depth indication is less accurate after narrowing.

Coil Drift:

If using PINPOINT mode for continuous searching, be aware that drift can occur over time, affecting sensitivity. Periodic retuning by pressing PINPOINT is required. Temperature changes can also cause coil drift. If the detector moves from a cooler to a warmer environment, it may emit a constant tone until the temperature stabilizes; retune if this occurs. If it moves from warmer to cooler, it may lose sensitivity (remain quiet); retune if this happens.

Ground Balancing

What is Ground Balancing?

All soils contain minerals. Ground mineral signals can be tens or hundreds of times stronger than signals from buried metal objects. Iron minerals and dissolved mineral salts in soil cause interfering signals.

Why do I need to Ground Balance?

Ground Balancing is the process by which the metal detector cancels unwanted signals from ground minerals while still detecting signals from buried metal objects. This is accomplished by calibrating the detector's phase response.

When calibrated to the soil, the detector provides deeper target detection, quieter operation, and more accurate target identification.

How to Ground Balance Your Detector (Preferred Method):

Find a patch of ground free of metal.

1. Rotate the Ground-Balance KNOB 100% clockwise to the Preset position.
2. Press the AUTO TUNE pad. "ALL-METAL" appears on the display.
3. Press the Sensitivity + pad several times to reach the highest "quiet" setting or a setting with a faint background hum.
4. Press Threshold + or - to adjust the audible hum to a comfortable level.
5. Physically pump the searchcoil and detector up and down over the ground. Lift the searchcoil about 6 inches above the ground and lower it to within 1 inch of the ground, about once or twice a second.
6. While pumping the searchcoil over the ground in this fashion, slowly rotate the KNOB counterclockwise.

Caution: Do not ground balance over a metal object.

Alternate Quick Ground Balancing Method:

This simpler method yields an approximate ground balance setting.

1. Find a patch of ground free of metal.
2. Set the ground-balance knob to the preset position (100% clockwise).
3. Position the searchcoil about 6" over the ground.
4. Press the PINPOINT button.
5. Lower the searchcoil to within 1" of the ground. The sound will get louder.
6. Rotate the knob slowly counterclockwise until the detector is just silent.
7. Rotate the knob back slightly clockwise until you hear a low-volume sound. At this low-volume setting, the detector is approximately ground balanced.

DD Coil Characteristics

A DD coil is superior to a concentric coil but may require a different sweep technique. Advantages include better target separation, superior performance in highly mineralized ground, and a broader sweep for covering more ground.

If you experience multiple responses on a shallow target, you can raise the coil or narrow the sweep over known targets to intersect only the center section of the coil.

Bottle Caps:

The disadvantage of the DD coil is its propensity to classify steel bottle caps as coins. If you hear a high tone in DISC mode and suspect a coin, use this method to check for a bottle cap:

1. If a repeatable ID# is around 68 to 72, it should be a dime or copper penny.
2. If not in that range:
1. Sweep the back end of the search coil over the target. If the tone changes from high to low, it is probably a bottle cap.
2. Sweep the search coil fast across the target. If the tone and ID-value drop, it is probably a bottle cap. The faster you sweep a bottle cap, the lower the tone.

The F4 is supplied with a standard 4" auxiliary search coil. This coil will not classify steel bottle caps in the 10¢ and higher coin categories, allowing them to be easily discriminated out.

Sweet Spot:

The "center" of the DD-Coil is elongated (elliptical) from top to bottom. With practice, you can find where the center of this ellipse lies on your coil. Use this center point as a reference in pinpointing.

Quick-Start Demonstration

Supplies Needed:

• A Nail
• A Pull-Tab from a beverage can
• A Nickel
• A Quarter
• A Zinc Penny (dated after 1982)

Position the Detector:

1. Place the detector on a table with the search coil hanging over the edge, or have a friend hold it with the coil off the ground.
2. Keep the search coil away from walls, floors, and metal objects.
3. Remove watches, rings, and other jewelry or metal objects from your hands and wrists.
4. Turn off appliances or lights that cause electromagnetic interference.
5. Pivot the search coil back toward the detector body.

Power Up:

Press the ON/OFF touch pad.

Wave Each Object over the Search Coil:

1. Notice a different tone for each object.
• Low Tone: Nail
• Low-Mid Tone: Pull-Tab
• Medium Tone: Zinc Penny
• High Tone: Quarter
2. Motion is required. Objects must be in motion over the search coil to be detected.

Press the DISC Touch Pad:

The detector will beep, and two "R"s will appear under the iron indicators.

Wave the Nail over the Search Coil:

The Nail will not be detected. It has been "Discriminated Out."

Press the "DISCRIMINATION +" Touch Pad 3 Times:

Five "R"s will now be displayed.

Wave All Objects over the Search Coil:

The Nail and Pull-Tab will not be detected. The other objects will be detected with their own distinctive tones.

Press the NOTCH Touch Pad:

A flashing "L" will appear under the IRON-1 segment.

Press the DISCRIMINATION + Touch Pad 3 Times:

The flashing "L" will move to the 5¢ segment.

Press the NOTCH Touch Pad Again:

The "R" will disappear under the 5¢ segment.

Wave the Nickel over the Search Coil:

The nickel is detected.

Wave the Penny over the Search Coil:

Press the NOTCH touch pad twice. The arrow under the 1¢ segment will flash, and then the "R" will illuminate.

Wave the Penny over the Search Coil Again:

The penny (the most recently detected item) is eliminated from detection.

Press the PINPOINT Touch Pad:

Hold one of the metal objects motionless over the search coil.

• All metal objects are now detected.
• One monotone sound indicates the presence of any type of metal.
• A 2-digit numerical display indicates approximate target depth, in inches.

Sensitivity Adjustment

Electromagnetic Interference (EMI)

Use the Sensitivity Control to eliminate Electromagnetic Interference (EMI). The F4 metal detector is extremely sensitive; the search coil creates its own magnetic field and acts like an antenna. If your detector beeps erratically when the search coil is motionless, the unit is likely detecting another electromagnetic field. Common sources of EMI include electric power lines, motors, household appliances like computers and microwave ovens, and dimmer switches. Other metal detectors also produce EMI; keep them at least 20 feet apart when detecting with a friend. If the detector beeps erratically, REDUCE THE SENSITIVITY by pressing the Sensitivity - pad.

In most urban environments, you should be able to search without chatter at the default sensitivity setting (4 bars) or one level lower. At maximum sensitivity, the F4 may "chatter" near power lines or electrical devices. You may be able to trace underground power lines by following rapid chatter when the searchcoil is near the ground.

To manage chatter:

1. REDUCE the SENSITIVITY until the chatter stops.
2. Try sweeping it over the ground. If the F4 chatters while held still or in the air, it may be much quieter when sweeping over the ground.
3. Operate in AUTOTUNE mode, which tolerates interference better, even at high sensitivity.

Severe Ground Conditions

The Sensitivity Control also reduces false detection signals caused by severe ground conditions. While the detector circuitry eliminates signals from most naturally occurring ground minerals, 100% of all ground conditions cannot be anticipated. Highly magnetic soils or high saline content soils can cause the detector to emit tones when no metal objects are present. If the detector emits false, non-repeatable signals, REDUCE THE SENSITIVITY.