Boost and Cache Locating Processes F75- Brochure

F75Comprehensive Operating Manual & Guide to Metal DetectingMetal DetectorCCoommpprreehheennssiivvee OOppeerraattiinngg MMaannuuaall&& GGuuiiddee ttoo MMeettaall DDeetteeccttiinnggACCESSORIES FOR COMPLETE DETAILS VISIT WWW.FISHERLAB.COM • 1-800-685-5050Fisher Padded Carry Bag Rugged double stitched construction. Includes handyexterior pocket for extra batteries or small accessories.103693000CFisher Stereo HeadphonesUse with Fisher metal detectors. Lightweight and adjustable withtrue stereo sound, adjustable volume, 1/8 jack with 1/4 adaptor,4’ cable. 9720950000Fisher Pin PointerPinpoints the exact location of buried metal objects. Audio signalindicator and vibrator. Runs on 1 – 9-Volt Battery. FPOINTMetal Sand ScoopLarge galvanized metal scoop with filtering holes.Strong Rubberized grip. SAND SCOOPLesche KnifeMade from high quality heat-treated tempered steel.The ultimate digging tool. Comes with a durable sheath.12" in length with a 7" serrated blade. LESCHE KNIFE Fisher Baseball Cap One size fits all. FCAP Fisher T-Shirt* 100% white cotton with Fisher® Logo. Sizes – LG, XL & XXLReplacement/Accessory Search Coils11” Biaxial Accessory Coil - 11COIL-F7510” Concentric Standard Coil (replacement)– 10COIL-F706.5” Concentric Accessory Coil - 6COIL-E5” Biaxial Accessory Coil - 5COIL-F75Coil CoversSpecially made to protect your coil from abrasion and damage.11” Biaxial Accessory Coil Cover – COVER-11DD10” Concentric Standard Coil Cover – F70COVER6.5” Concentric Accessory Coil Cover- 6COVER-E5” Biaxial Accessory Coil Cover - 5COVER-CZ3Fisher® Face Rain CoverSpecially made to protect your F70 from weatherGoldProspecting Kits*Image not shown.M75 Rev.3 121412F75-MANUAL(122811).qx 12/14/12 9:03 AM Page 1 2 43F75Comprehensive Operating Manual & Guide to Metal Detecting Comprehensive Operating Manual & Guide to Metal DetectingF75The F75 is a multipurpose metal detector. Its most popular uses are coinshootingand relic hunting, and it is also well-suited to gold prospecting.PRODUCT FEATURES• Light weight and well-balanced: best ergonomically engineered detector in theindustry.• Intuitive menu-driven user interface• Large LCD screen • Visual indicators of important values such as:Target IdentificationTarget ConfidenceTarget Depth (both running-depth and pinpoint-depth)Ground Mineralization• Multiple Search Modes:DiscriminationStatic All-MetalMotion All-Metal• Trigger-actuated FASTGRAB™ ground balancing with manual override• Waterproof 11-inch open-frame BiAxial™ searchcoilHousing constructed of a carbon fiber-polycarbonate blend• Trigger-actuated target pinpointing with variable audio pitch • Fully Adjustable Armrest• Display backlight for night and low-light conditions• Notch and discrimination controls• Covers provided for both the control housing and battery box.• Made in the USAIf you have any questions, or need assistance with your metal detector,Call 1-915-225-0333, and ask for Fisher Hobby Technical ServiceCopyright Fisher Research Labs, Inc.5-Year Limited WarrantyThe F75 metal detector is warranted against defects in materials andworkmanship under normal use for five years from the date of purchase to theoriginal owner. Damage due to neglect, accidental damage or misuse of this product is notcovered under this warranty. Decisions regarding abuse or misuse of thedetector 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 our option,the metal detector returned, shipping cost prepaid, to Fisher Labs. Shippingcost to Fisher Labs is the responsibility of the consumer.To return your detector for service, please first contact Fisher Labs for a ReturnAuthorization (RA) Number. Reference the RA number on your package andreturn the detector within 15 days of calling to:Fisher Research Labs, Inc.1465-H Henry Brennan Dr.El Paso, TX 79936Phone: 915-225-0333 ext.118Fax: 915-225-0336Warranty coverage does not include the cost of transporting the detector backto an owner who is located outside of the United States of America.NOTE TO CUSTOMERS OUTSIDE THE U.S.A.This warranty may vary in other countries, check with your distributor for details.Warranty does not cover shipping costs.According to FCC part 15.21 Changes or Modifications made to this device not expressly approvedby the party responsible for compliance could void the users authority to operate this equipment.This device complies with FCC Part 15 Subpart B Section 15.109 Class B.Copyright© 2011 by Fisher Research Labs, Inc.All rights reserved, including the right to reproduce this book, or parts thereof, in any form.Published by Fisher Research Labs, Inc.Fisher® is a registered trademark of Fisher Research Labs, Inc.www.fisherlab.com1465-H Henry Brennan Dr., El Paso, TX 79936 • (915) 225-0333F75-MANUAL(122811).qx 12/14/12 9:03 AM Page 2 42 3F75Comprehensive Operating Manual & Guide to Metal Detecting Comprehensive Operating Manual & Guide to Metal DetectingF75Table Of ContentsSpecifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4Quick-Start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5MechanicalsAssembly Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-7Mechanicals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8Armrest adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8Using Headphones (not included) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9Introduction to the F75General information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-12Menu System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13Ground Balancing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-16Motion All Metal Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17Static All Metal Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18Discrimination Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19-22PinPoint Feature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23LCD Visual Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24-26Numeric Target Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24Probable Target Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . .24Target Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25Depth Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25Confidence Indicator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25Fe3O4 Graph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25Battery Indicator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26G.B. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..26Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26 Frequency Shifting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27Capabilities & Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28-30Tips & TechniquesSearch TechniquesHow to sweep the searchcoil . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31Pinpointing targets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31Estimating target size and depth . . . . . . . . . . . . . . . . . . . . . . .31-32False signals and chatter . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33-34Adjusting Sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34Tips on ground balancing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35Detecting ActivitiesCoinshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36Relic Hunting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37-38Gold Prospecting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38-39Cache Hunting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40Shallow Water Hunting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40-41Salt-Water Hunting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41How metal detectors work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42Warranty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Back PageHow Metal Detectors WorkMost hobby metal detectors use VLF Induction Balance technology. Here's how they work.The searchcoil (also called search head or loop) contains two electrical induction coils whichare like antennas. One coil transmits a rapidly alternating magnetic field, illuminating theregion surrounding the searchcoil. If metal is present, its electrical conductivity distorts themagnetic field. If iron metal is present, its magnetism also distorts the magnetic field, but in adifferent way, allowing the metal detector to distinguish between ferrous and nonferrousmetals. The other coil is a receiving antenna which detects changes in the magnetic field caused bythe presence of metal. Electronic circuits amplify this weak signal, analyze it to determine thechanges which occur as the searchcoil sweeps over the target, and then convey theinformation to the user in the form of a visual display or audio tones. Most modern metaldetectors 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 theweak signals of small or deep objects. This can cause the object to go undetected, or to bemisidentified when it is detected. Much of the technology that goes into modern metaldetectors is devoted to the task of eliminating the unwanted signals from iron minerals in thesoil, while not losing the signals from metal objects.This device has been designed to operate with the antennas listed below, and having amaximum gain of 3 dB. Antennas not included in this list or having a gain greater than 3 dBare strictly prohibited for use with this device. The required antenna impedance is 53 ohms.10COIL-F70, 11COIL-F75, 5COIL-F75, 6COIL-EThe following statement is not relevant to metal detectors but is printed here to satisfylegal notification requirement:“To reduce potential radio interference to other users, the antenna type and its gain should beso chosen that the equivalent isotropically radiated power (e.i.r.p.) is not more than thatpermitted for successful communication.”The following countries allow free movement of this product within the European community:FIN,LVA,SVN,SUI,BIH.F75-MANUAL(122811).qx 12/14/12 9:03 AM Page 3 4 41F75Comprehensive Operating Manual & Guide to Metal Detecting Comprehensive Operating Manual & Guide to Metal DetectingF75SpecificationsMechanical: S-rod with electronics housing mounted on handgrip, 3-piecebreakdown, batteries under elbow, 2-way armrest adjustment —forward/backward & around forearm.Searchcoil: 11” (28 cm) open-frame elliptical double-D, waterproof.Batteries: 4 AA, alkaline (not included).Weight: 3.5 pounds (1.6 kg) with alkaline batteries installed.Static Balance: force in vertical plane normal to elbow 0.47 pounds (0.22 kg).Varieswith adjustment and user’s stance and arm/hand physiology.Dynamic Balance: axial moment, 0.29 foot-pounds (0.39 newton-meters). Varies withadjustment and user’s stance and arm/hand physiology.Sweep Effort: lateral moment 5.2 foot-pounds (7.1 newton-meters).Operating Principle: VLF induction balanceOperating Frequency: nominal 13 kHz, quartz crystal timing reference13158Hz, 13100Hz, 1043Hz, 12987Hz, 12931Hz, 12876Hz, 12821HzBasic Sensitivity: 6 x 10 9 root Hertz (detectivity)Lag Coefficient: 78 millisecondsReactive Overload: approximately 10,000 micro-cgs units (volume susceptibility)40,000 micro-cgs units with sensitivity < 30.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, inclusiveDiscriminationGround Suppression: combination of second and third order methodsID Ground Suppression: third orderBattery Life: Typically 40 hours with high quality alkaline batteriesEstimated 80 hours with nickel oxyhydroxide batteriesEstimated 65 hours with lithium iron disulfide batteriesOperating Temp Range: 4 to +122 degrees F (-20 to +50 degrees C)Operating Humidity Range: 0-90% non-condensingWhen searching on a beach, it is best to either search in Motion All Metal mode, or to searchwith the discrimination level set just high enough to eliminate iron, because the value of beachfinds is largely in the jewelry rather than in the coins. You will dig a lot of aluminum trash, butthe digging is easy, and you can tell people that you are helping to clean up the beach andmake it safer for people's feet. We recommend the use of a special sand scoop for recoveringvaluables from the sand quickly -- most metal detector dealers sell these.The electrical conductivity of the water itself can pose some challenges. You may get falsesignals when going into and coming out of the water, making it necessary to pay carefulattention to keep the coil either in or out of the water, but not to touch the surface. This effectmay be observed in either fresh or salt water. Salt Water HuntingSalt water is highly conductive, and produces a strong signal which is like that of metal. The F75 is not specifically designed for high performance in salt water, but can be used in thisenvironment.If you desire to search in or over salt water, the following measures will usually be sufficient tosilence the salt water response while retaining acceptable sensitivity:1. Set the sensitivity in both modes to less than 30.2. Ground balance the machine manually in Motion All Metal mode.3. Search in the Discrimination mode with a discrimination setting higher than 25.Treasure Hunter’s Code of Ethics:• Always check Federal, State, County and local laws before searching• Respect private property and do not enter private property without the owner’s permission.• Take care to refill all holes and leave no damage.• Remove and dispose of any and all trash and litter found.• Appreciate and protect our inheritance of natural resources, wildlife and private property.• Act as an ambassador for the hobby, use thoughtfulness, consideration and courtesy at alltimes.• Never destroy historical or archaeological treasures.• All treasure hunters may be judged by the example you set; always conduct yourself withcourtesy and consideration of othersCopyright Fisher Research Labs, Inc. 2011.Detecting Activities (continued)Shallow Water Hunting (continued)F75-MANUAL(122811).qx 12/14/12 9:03 AM Page 4 40 5F75Comprehensive Operating Manual & Guide to Metal Detecting Comprehensive Operating Manual & Guide to Metal DetectingF75Quick StartUse your F75 right out of the box1. Assemble the detector (see instructions beginning page 4).2 Install four AA alkaline batteries. All positive (button-end) terminals point up. 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 F75 starts out in the Discrimination mode, with:Sensitivity preset to 60Discrimination Level preset to 10Number of Tones preset to 3Process# preset to dESweep the searchcoil from side to side, parallel to the ground. Keep the searchcoil moving over the ground. If you stop moving the searchcoil, the sound will also stop.Probable target type will be indicated at the top of the LCD screen.5. If the searchcoil is not in motion and not close to metal, the detector should besilent.6. If you experience false signals from electrical interference, from the soil itself, orfrom lots of trash metal, press the MENU button.Sensitivity will be highlighted.Rotate the Settings knob to the left (counterclockwise),Reduce the sensitivity setting until the false signals go away.After 7 seconds, the machine will exit the menu and return tonormal operation.7. Find a patch of ground free of metal, toss a coin on the ground and sweep back and forthover it a few times to get a feel for how the machine responds.8. You are now ready to search. 9. Pull and hold the trigger switch with your index finger to pinpoint the exact location oftargets, making them easier to unearth.When the trigger is pulled, PinPoint is engaged ….The searchcoil need not be in motion to detect an object.The 2-digit numeric display indicates approximate target depth, in inches.Cache Hunting A cache (pronounced "cash") is an accumulation ofmoney, jewelry, gold, or other valuables, which someonehas hidden. When people bury a cache, they usually putit in a strongbox or in a jar. To search for a cache, youfirst need a reason to believe the cache may exist. Thismeans doing research. Some caches have been thesubject of many stories you can read about in print, butyou need to be able to sort fact from fiction. If you can getcopies of old newspaper stories about the circumstancessurrounding the hiding of the cache, you may finddiscrepancies which help you to judge the reliability of theinformation available. Often the best information on anold cache is to be learned from old timers who live in thearea where the cache is thought to be. In the case ofnewer caches, often the only information is what can beobtained from family and acquaintances of the personwho is believed to have hidden the cache.The ownership of a cache is not always clear. Sometimesit belongs to the person or heirs of the person who hid it,sometimes it belongs to the owner of the property on whichit is located, and sometimes it belongs to the person whofinds it -- or some combination of the above. If the contentsof the cache were stolen, this fact can also complicate thequestion of ownership. Find out what laws apply to thecache in question, and always make sure that the issue ofownership is resolved prior to recovering a cache.Compared to a coin, a cache is usually large and deep. Searching in Motion All Metal mode isrecommended. However, for a really deep cache, it may be advantageous to search in STATmode, frequently pulling the trigger momentarily to maximize sensitivity. Shallow Water HuntingAll Fisher Research Labs searchcoils are waterproof, allowing you to search in shallow waterabout two feet deep. If searching around water, be careful not to get the electronics housingwet. Avoid salt spray, as it will work its way into the control housing and damage theelectronics -- such damage is not covered by the warranty.Both fresh and salt water beaches are popular places for metal detecting. Vacationers losemoney and jewelry playing in the sand and in the water. It is usually easy to dig in a beachenvironment, and metal detecting is permitted on most beaches. Occasionally you may beable to help someone recover a piece of jewelry they have lost minutes before; this is agratifying experience.Detecting Activities (continued)F75-MANUAL(122811).qx 12/14/12 9:03 AM Page 5 6 39F75Comprehensive Operating Manual & Guide to Metal Detecting Comprehensive Operating Manual & Guide to Metal DetectingF75AssemblyIs easy and requires no tools.1. Position detector upright.2. Rotate the LOCKING COLLARfully counterclockwise.3. Insert your finger inside the tubeand make sure the INTERNALCAM LOCK is flush with theinside of the tube.4. Insert the MIDDLE STEM into theS-ROD.5. Rotate the MIDDLE STEM untilthe SILVER BUTTON locates inthe hole.6. Twist the LOCKING COLLAR fully inthe clockwise direction until it locks.7. If your detector has 3 tubes and 2Locking Collars, repeat this process on theLower Stem.8. Position the Lower Stem with the Silver Buttontoward the back.Using the Bolt, Single Rubber Washer, andKnurled Knob, attach the Searchcoil to theLower Stem.9. Adjust the Lower Stem to a length thatlets you maintain a comfortable uprightposture, with your arm relaxed at yourside, and the Searchcoil parallel to theground in front of you.10. Wind the Cable securely around theStems.A loose or moving Cable can cause falsesignals.Release Clip Battery Compartment Hand-grip 2-way adjustable armrest On/Off & Volume Switch Menu Botton Headphone Jack SearchCoil CableSettings Switch Biaxial Searchoil Dual-functionTrigger switchS-RodLockingCollarLockingCollarVelcroStrapVelcroStrapCablePlugMiddleStemLowerStemBecause most gold nuggets are tiny, and are usually found insoil which is high in iron oxide minerals, serious goldprospecting requires a detector with high sensitivityand true ground balanced motion all metaloperation. Run the machine with the sensitivityhigh enough to hear some noise from groundminerals, and learn the language of thesounds you hear. Headphones arerecommended unless consideration forsafety (for instance rattlesnakes)rules them out. Move thesearchcoil slowly and deliberately,carefully controlling its heightabove the ground to minimizenoise from iron minerals in thesoil. If you hear ground noise, yourGround Setting could be a bit off,so perform the ground balancingprocedure again. As you walk even a very shortdistance, ground conditions can change. Theground geology typically associated with gold willtend to change over very short distances.The Fe3O4 bar graph indicates the amount of ironmineralization in the soil. In most gold fields, especiallyalluvial (placer) deposits, gold tends to be associated withiron minerals, especially magnetite black sand. If you knowthis to be the case in the area you're working, you canmaximize your gold recovery by concentrating your efforton areas where the bar graph indicates higher amounts ofiron mineralization. Gold prospectors are mostly a friendly bunch, and willing to spend some time showing abeginner how to increase his odds of finding the yellow stuff. Many will invite you to search ontheir claims (if they have any) once they get to know you. In some gold areas, a lot of theterrain is under claim, so you need to learn how to recognize posted claims and stay off of themunless you have the claim owner's permission. Prospecting clubs such as the GPAA often ownclaims which are open to their members, and sponsor group outings to good gold areas.It’s a thrilling experience to dig into the ground and pull out a precious piece of yellow metalthat you are the first person on earth to see. If you love being outdoors, have patience, andcan stay motivated by the prospect of finding that next nugget, then beeping for gold may bethe hobby for you. While only a few get rich prospecting, if you are not among them, think of itas outdoor recreation where your finds defray the expense of having fun Detecting Activities (continued)Gold Prospecting (continued) F75-MANUAL(122811).qx 12/14/12 9:04 AM Page 6 38 7F75Comprehensive Operating Manual & Guide to Metal Detecting Comprehensive Operating Manual & Guide to Metal DetectingF7511. Connect Cable Plug to housing.Do not twist the Cable or Plug. Turn Locking Ring only. Use minimal finger pressure tostart the threads. Do not cross-thread. When the Locking Ring is fully engaged over thethreaded connector, give it a firm turn to make sure that it is very tight. When the LockingRing is fully engaged over the threaded connector, it may not cover all of the threads. 12. Tighten both Locking Collars.13. Secure the Cable with the 2 Velcro Straps provided, one on the Lower Stem close to theSearchcoil, and one on the Upper Stem, close to the housing. Leave just enough slack inthe Cable, at the Searchcoil end, to be able to rotate the Searchcoil a small amount aboutthe Bolt. After full assembly and upon first use in the field, check this adjustment. It isvery important to keep the Cable secure against the Stem, especially at high Gain, asmovement in the Cable may cause false signals.Assembly (continued)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 Fe3O4 bar graph features of the F75 can be used to map the soilsof a site. In this way you might determine which areas have been dug, backfilled, or subjectedto 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 oldnewspapers, and seek information on the internet. Where did buildings used to be? Whichhave since been torn down? Where did people gather for public events like dances and countyfairs? Where did train and stage lines run? Where were the swimming holes? In almostevery town there is a historical society and museum of local history. Most museums aregrateful 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 ormuseum, 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. The propertyowner can often be persuaded that the site should be searched immediately while it is stillsearchable. Gold ProspectingIn the United States, gold is found in many places in the western states, Alaska, and in a fewlocalities in the Appalachians. The old saying "Gold is where you find it", means that to findgold, you should look in areas where the yellow metal is known to be present. Hillsides are the best areas for gold prospecting using a metal detector, because hillsidescannot be cleaned out by panning and dredging the way streams can. Also, gold on hillsides,not far from its source vein, tends to be larger, and hence more readily detected, than alluvial(placer) gold which tends to get pounded to pieces and worn away as it rolls along thestreambed with gravel during floods. Gold is valuable because it is a scarce commodity. Evenin a good gold producing area, you will often spend an entire day without finding any gold.Meanwhile you will dig bits and pieces of other metal-- birdshot, shells and bullets fromhunting and target practice, bits of rusted barbed wire, chips off shovels and other miningtools, rusted tin cans, etc. Hot rocks -- rocks containing concentrations of iron oxides thatsound like metal when you pass over them -- are also a nuisance in many gold areas.Discrimination is usually ineffective because the loss of sensitivity resulting from discriminationis enough to cause those little nuggets to vanish. If you have gone many hours without findinggold and are wondering if there is something wrong with your metal detector or how you areusing it, the most important clue is this: if you are digging tiny pieces of trash metal, then ifgold were present you would have found small gold pieces too Detecting Activities (continued)Relic Hunting (continued)F75-MANUAL(122811).qx 12/14/12 9:04 AM Page 7 8 37F75Comprehensive Operating Manual & Guide to Metal Detecting Comprehensive Operating Manual & Guide to Metal DetectingF75MechanicalsBATTERIES (not included)The F75 requires four AA batteries.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.DO NOT MIX OLD AND NEW BATTERIESExpect 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, butwhen 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. Otherwisebattery life will be determined by the weakest battery, because the good batteries cannotdeliver 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. IMPORTANT: To avoid stressing the battery spring connection, install the batteries using this technique:1. Position the bottom (negative) side of the battery on top of the spring.2. Do not install the top of the battery into the compartment yet.3. Push down on the battery to compress the spring.4. With the spring compressed a bit, then tip the battery upright and push back into the compartment.12Detecting Activities (continued)Relic HuntingRelic hunting is searching for historical artifacts. Themost common desired objects are battlefield debris, coins,jewelry, harness hardware, metal buttons, trade tokens,metal toys, household items, and tools used by workmenand trades people. The most common unwanted metal isiron (nails, fence wire, rusted cans, etc.), but some ironand steel objects such as weapons may be valuable. Ifyou are at a site where you may encounter unexplodedordinance, use caution.Most relic hunting locations are in fields, forested areas andvacant lots where digging holes will not damage turf grass, sohaving a detector with good depth sensitivity is important. Someplaces are so littered with iron that it is necessary to discriminateout iron in order to be able to search, even though you may misssome 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 tomake sure it's not illegal. Certain kinds of sites, on both public andprivate land, are protected by law from relic hunting. If there is ametal detecting club in your area, some of the members will probablyknow what the laws are in that area and which sites are, and arenot, off limits. Relic hunting is most rewarding if you have an avid interest inhistory. In many cases, the value of a relic is not the object itself,but the story it's a part of -- what historians call context andarcheologists call provenance. A few pieces of rusty metalcan tell the story of life in a specific place, or that of aspecific family or person from hundreds of years ago.They can capture our imagination and help to give contextto our lives today. The value and context of a find can be readily lost withoutproper documentation and storage. Add finds to yourcollection with care. Take the trouble to understand thesite you are searching and keep track of where you findthings. Describe exactly how and where items wherefound. Consider including a sketch of the site with yourfinds. Organization techniques might include storing togetherall finds from the same site. Alternatively, if you have anF75-MANUAL(122811).qx 12/14/12 9:04 AM Page 8 36 9F75Comprehensive Operating Manual & Guide to Metal Detecting Comprehensive Operating Manual & Guide to Metal DetectingF75ARMRESTThe armrest WIDTH and POSITION are bothadjustable.Armrest Width: The sides of the armrest canbe bent inward and outward.To best stabilize the detector to your armand body movement, squeeze the sidesof the armrest around your forearm. For avery secure fit, some users prefer to bendthe armrest in tightly against the forearmsuch that you pry the sides loose eachtime you place your arm into the armrest.Armrest Position on Pole: Remove the twobolts to position the armrest farther forward or back, to adapt to your arm’s length. -- To reinsert the bolts, spin and twistthem into place. Be careful not todamage the power cable that runsthrough the aluminum tube.-- Insert both bolts completely throughboth sides of the bracketbefore attaching the nut to theopposite side. -- After reinserting the bolts, tighten themvery securely. You may need to usegloves for a firm grip. As you swing the detector from side-to-side, you want the boltstight enough so that you do not feel any movement between the pole and armrestmounting bracket.If you notice unwanted movement while swinging 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 F75 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 stereo plugshould work; headphones with a mono plug will not work. This device is to be used withinterconnecting cables/headphones shorter than three meters.Using headphones 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 ina noisy location. For safety reasons, do not use headphones near traffic or where otherdangers, like rattlesnakes, are present.Mechanicals (continued)Adjust the armrest in or out accordinglyAdjust the armrest forward or back, to adaptto your arm’s length.Detecting ActivitiesCoinshootingCoinshooting is searching for coins, usually in places like parks, schoolyards, churchlawns, and people's yards. In most places where coins are likely to be found, thereis also a lot of aluminum trash like pull-tabs and bottle caps, as well as steelbottle caps and often nails. Sometimes there is jewelry present. You willusually search using discrimination to get rid of the iron and thealuminum trash, even though this mode will cause you to miss some ofthe jewelry.Much coinshooting is done in lawn areas, where digging holeswould cause damage to the grass. We recommend use of anaccessory hand-held pinpointer in such cases. Recovering targets isusually done by first accurately pinpointing the target, then carefully cuttinga slit in the turf with a knife, and tamping it firmly when you are finished. Inthese situations, you cannot recover deep targets for fear of damaging theturf, so you can cut down on nuisance signals by reducing the sensitivity. When searching on private property, first get the permission ofthe property owner. Most of the public places where one islikely to do coinshooting are city, county, or school districtproperty. There is usually no ordinance prohibiting use ofa metal detector as long as you are not causing damage.Sometimes such ordinances do exist. Administrators andsecurity personnel often have the legal authority toprohibit any activity they do not like even if there is noordinance against it. If there is a metal detecting club in yourarea, someone will usually know what areas can and cannotbe searched. If you are ever in doubt about hunting anarea, then ask before hunting.Be prepared to always put your best foot forwardwhen using a metal detector in a public place. Pickup any trash you recover; put it in a pouch or pocketedapron. This way you can explain that you are performinga public service by helping keep the place free of trash,especially pieces of metal or glass that could endanger a child atplay. Be proficient at recovering targets without causingdamage to the lawn. Explain that whenever you find jewelrywhich has personal identification marks, such as a classring, you make an attempt to determine the owner and toreturn it. When someone who questions what you aredoing understands that you are causing no damage and areactually performing a public service, you will usually bewelcome. F75-MANUAL(122811).qx 12/14/12 9:04 AM Page 9 10 35F75Comprehensive Operating Manual & Guide to Metal Detecting Comprehensive Operating Manual & Guide to Metal DetectingF75Introduction to the Fisher F75HIGH PERFORMANCE The F75 is a multi-purpose high-performance computerized metaldetector. It has the high sensitivity and ground balancing control needed for professionalgold prospecting, the discrimination responsiveness needed for serious relic huntingunder 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 tocoins. The F75 comes with an 11-inch elliptical Bi-Axial searchcoil for maximumdetection depth in mineralized soils. USER COMFORT The F75 is among the lightest and best balanced of all high-performancemetal detectors, so you can hold and swing it almost effortlessly. The armrest position isadjustable to fit your arm. The grip is durable high-friction foam elastomer, comfortable inany 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 theLCD display. The LCD display indicates the electrical signature (Target I.D.) of thedetected metal object. The display provides continuous information on battery conditionand on ground mineralization, which affects detection depth. Help messages areautomatically displayed on the bottom of the display when necessary.LOW OPERATING COST The F75 is powered by four AA alkaline batteries, which willtypically 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 UnderwaterDetector, FX3 magnetometer, the Gemini 2-box locator, the XLT-16 Acoustical LeakDetector, and the XLG-80 Ultrasonic Leak Detector. John and David were supported byfellow electrical engineers Jorge Corral, and Mark Krieger. The mechanical design was acollaboration among David Johnson, Brad Fulghum, John Griffin, and Tom Walsh.MECHANICAL ENGINEERINGWhile the F75 is robustly engineered for outdoor use, it is not indestructible and it is notwaterproof. RESET functionThe F75’s microprocessor saves all settings which you input, even after the power isturned 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 andpush-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)If, while searching, you are constantly getting signals from which you cannot recover metaltargets, you may be detecting small or deep targets which are not recoverable using themethods at hand. So, you may do better if you reduce the Sensitivity setting.Tips on ground balancing When the F75 first turns on, the ground balance setting is preset to 90. This will give apositive response on nearly all soils. If you search in the Discrimination mode, you willprobably not have to balance to the ground. If you switch to All Metal mode, ground balancingwill 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 ispresent. Locate what seems to be a clear area and then Ground Balance. Ground Balancingmay be done automatically by pushing the trigger, or manually if you are in All Metal mode.After you have ground balanced, sweep back and forth to see if there is little or no audibleresponse to the soil. This is best done either in All Metal mode, or in Discrimination mode withdiscrimination set to zero. Alternatively, use the PinPoint trigger to check the spot. If there islittle 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 anotherpromising spot and try again. If you cannot find a spot to successfully ground balance, it is timeto give up. Reset the ground setting to 90 and then use the machine without ground balancing.In most areas, once you have ground balanced, the ground balance setting will remainsatisfactory for a long time. However, if the soil has been disturbed by digging or the additionof fill dirt, or if you are in a geologically complex setting such as is commonly encountered ingold prospecting areas, you may have to frequently perform the ground balancing procedureto accommodate changing soil conditions. When you ground balance, the numerical Ground Setting will momentarily appear on the LCDscreen. In general, sandy or gravelly soils will tend to read in the 75-95 range, light coloredloams 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 grainedthe soil is, the lower the numeric reading will be.The Fe3O4 bar graph indicates how much iron mineralization is present. For it to work, thesearchcoil must remain in motion. The most accurate readings will be achieved by pumpingthe coil as you do when ground balancing. The higher the mineralization, the greater thenecessity 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 thesite. Then collect data. Ground Balance to document mineral type; view mineral amount onthe Fe3O4 bar graph. Then plot the data on the site map and draw isolines. In this way youmay be able to locate areas which have been dug, backfilled, or subjected to fire. Thisinformation in turn helps to reveal the history of the site.F75-MANUAL(122811).qx 12/14/12 9:04 AM Page 10 34 11F75Comprehensive Operating Manual & Guide to Metal Detecting Comprehensive Operating Manual & Guide to Metal DetectingF75ControlsON-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 electricalinterferenceOn/Off &VolumeSwitchMenuAccessToggle FrombP or CL ProcessSettingsKnobDual-functionTrigger switchDUAL FUNCTIONMENU BUTTONSearch Techniques (continued)In spots where there has been intense fire, such as a campfire site or where a stump wasburned during land clearing, the soil minerals may be altered by oxidation so that their groundbalance setting is lower than that of the surrounding soil. In such cases, search slowly andchange the G.B. setting as frequently as necessary. In some areas, electrically conductive industrial minerals such as fuel coke, slag, clinkers (left overfrom burning mineral fuels), or charcoal have been dumped or used as landfill. Individual lumps ofthese materials can usually be quieted by reducing sensitivity and searching with a discriminationlevel of at least 25. However, where the ground consists primarily of such materials, you may notbe able to search quietly. In that case, do not dig unless a signal is crisp and repeatable.Electrically conductive natural minerals such as graphite, graphitic slate, or sulfide ore mineralsare rarely encountered except when gold prospecting. When gold prospecting, you need to beable to hear everything, and you can expect to dig conductive minerals that turn out not to begold. In a given locality you may learn to recognize what type of rocks these minerals arefound in, and to ignore them if people in the area say that gold is not found in rocks of that type.HOT ROCKSA hot rock is a rock which causes the metal detector to sound off because the rock containsiron minerals. They come in two basic types.Negative hot rocks (also called cold rocks) are usually magnetite or contain magnetite, andgive a negative response because their ground balance value is a higher number than the soilthey are found in. They tend to be dark in color, usually black, and usually heavy. In somecases they will have rust stains. They are usually attracted to a magnet, and for this reasongold prospectors always carry a magnet—the ultimate ferrous/nonferrous discriminator. InMotion All Metal mode, negative hot rocks produce a boing sound rather than the zip sound ofa 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 weatheringprocesses so that their Ground Balance number is a number lower than the soil they arefound in. They are often small, right on the surface, sound just like a gold nugget, and arecommon in many gold prospecting areas. They are usually, but not always, drawn toa magnet. They are most often reddish in color but are often black, brown, or yellow. Onrelic hunting sites, red clay bricks and rocks which have lined a fireplace or a campfire willoften be hot rocks. The discriminator will usually eliminate them without difficulty if widelyscattered, but if there is a large concentration of them, the discriminator may not quiet themall. In that case, you can revert to the rule of thumb -- “don’t dig non-repeatable signals”.Using the sensitivity controlWhen the F75 is first turned on, the Sensitivity is at a medium setting appropriate for mostcoinshooting. 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 orelectronic appliances, or another metal detector, it is usually necessary to reduce theSensitivity setting to achieve quiet operation. Alternatively, use the Frequency Shift featuredescribed earlier in this manual.F75-MANUAL(122811).qx 12/14/12 9:04 AM Page 11 12 33F75Comprehensive Operating Manual & Guide to Metal Detecting Comprehensive Operating Manual & Guide to Metal DetectingF75Controls (continued)The F75 has two controls on the front panel, MENU and SETTINGS.MENU Pushbutton (Red button on right of the front panel) 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 SETTINGS knob then allows you to change values for the highlighted selection.2. Recall the last setting which you adjusted.After you have adjusted a setting, an indicator will remain highlighted next to this menuselection. One push of the button will recall that selection and display the stored value.This recall function is useful for a value you want to adjust frequently, such as the ground balance setting. In order to adjust a stored value with the SETTINGS knob, youmust first press the MENU button to reactive the user interface.SETTINGS Knob (On the left of the front panel)Rotate the SETTINGS knob to:1. Change the setting (or value) of the highlighted menu selection you have chosen. 2. Select the operating MODE when the top line of the menu is highlighted.When used to switch back and forth between the DISCRIMINATION mode and ALL METALmodes, the detector changes modes as soon as the corresponding selection is highlighted.The All Metal modes are used to detect all metal objects, including small or deep objects.Use the Discrimination mode to ignore trash metal such as nails, foil, or pull-tabs.NOTE: When the menu selection highlight disappears, the SETTINGS knob is deactivated.If settings values do not change when the SETTINGS knob is rotated, press the MENU buttonto reactivate the user interface. TRIGGER SWITCH (Under the display in front of your hand) While the trigger is pulled back, metal objects are temporarily detected without the need forsearchcoil motion. This aids in pinpointing the exact location of objects which were foundwhile searching in the Discrimination or motion All Metal modes. When in static all metals mode, pulling the trigger zeroes the audio threshold to the signallevel currently preset. If the searchoil is up in the air away from metal, this maneuver correctsfor threshold drift due to temperature changes.When the trigger is pushed forward, FASTGRAB automatic ground balancing is activated. Theinternal computer measures the magnetic properties of the soil in order to cancel interferencefrom naturally-occurring minerals in the ground. After the detector measures the soil in thismanner, the detector then uses this information to control operation in both the All Metal andDiscrimination search modes. FASTGRAB can be used at any time during operation.Search Techniques (continued)False Signals and ChatterAt times the detector may beep when there is nothing there, or it may seem like there isnothing there. There are five major causes for this: electrical interference, nuisance buriedobjects, ground minerals, hot rocks, and sensitivity set so high that internal circuit noise isaudible. The problem can usually be corrected by reducing the sensitivity setting, butsometimes other measures can also be taken.ELECTRICAL INTERFERENCEElectrical Interference can be caused by power lines, appliances, computer equipment, cell phones,fluorescent and vapor type lamps, household light dimmers, other nearby metal detectors, electricfences, radio transmitters, and electrical storms. If you get abnormal noise while holding thesearchcoil motionless in the air, the cause is either electrical interference or internal circuit noise. Ifit is electrical interference, by walking around with the metal detector, you can often follow thesignal and track it back to the offending device; simply turn the device off, or come back at anothertime when it may be off. If the interference is from power lines, you might try another time of day.Interference on power lines is usually caused by something connected to them which may be idlein the evenings or on weekends. If the interference is from a communications or broadcasttransmitting antenna, reducing the sensitivity is usually your only recourse. The F75 allows you to shift operating frequencies to avoid electrical interference. See theFrequency Shifting section for information about this technique.NUISANCE BURIED OBJECTSIn some areas there is a lot of metallic trash which produces weak signals. These couldinclude deeply buried objects, little bits and pieces of rusty iron and corroded foil. These itemscan be detected, but are difficult to pinpoint due to their depth and small size. When you digand find nothing, it may seem like the machine is beeping at nothing even though there isactually 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 searchcoil 2inches away from the ground. Trash objects very close to the searchcoil will sometimes not becompletely 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 objectsnear each other, the detector can be fooled into thinking that the gap between them is nonferrousmetal. This is a common condition where a wooden building has burned or been torn down, andthe site is littered with nails. A signal from a nonferrous metal object such as a coin will usually berepeatable, whereas a false positive signal resulting from multiple or oddly shaped iron objects willseem to wander around and even to vanish. Experienced detectorists call these non-repeatingsignals and usually do not bother digging them since nonrepeating signals are almost always trash.GROUND MINERALS Conductive mineral salts usually produce broad signals which will not be mistaken for ametallic object. Common causes are concentrations of mineral fertilizer, spots whereevaporation 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. Oceanbeaches have salt water—that subject is discussed toward the end of the manual.F75-MANUAL(122811).qx 12/14/12 9:04 AM Page 12 32 13F75Comprehensive Operating Manual & Guide to Metal Detecting Comprehensive Operating Manual & Guide to Metal DetectingF75The Menu SystemThe entire menu is printed on the LCD display. The display highlights the mode and settingswhich are in use. There are three search modes, Static All Metals, Motion All Metals, and Discrimination. Tochange between an All Metals mode and Discrimination mode, the top line of the menu systemmust be highlighted. Press the MENU button until the top line of the menu is highlighted.When either All Metal or Discrimination is highlighted, rotate the SETTINGS knob to movebetween the two categories.Each search mode has several adjustable function settings: ALL METAL: Threshold (not adjustable in stat mode), Audio Pitch, Sensitivity, andManual Ground BalanceDISCRIMINATION: Sensitivity, Discrimination Level, Notch, Number of Tones, and Process Number. To select a function, push the MENU button and continue pushing in order to move to thefunction you want. The word SETTING will pop up in the middle of the display, and thepresent setting of that function will be displayed as a number. To change a setting, rotate the knob.To increase a value, rotate to the right (clockwise)To decrease a value, rotate to the left (counterclockwise)If you select a function anddo not make a change tothat function after 7seconds, the detector willexit the menu systemautomatically, deactivatethe SETTINGS knob, andresume normal operation. If you press the MENUbutton while the machine isin normal operation, theuser interface will return tothe last menu featuresetting. This feature allowsyou to have quick access toa function that you want toadjust frequently. Search Techniques (continued)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 quarters. Their large size will produce astrong signal, tricking the microcomputer into thinking that it is a shallow coin. The following explains techniques for differentiating buried aluminum cans from coins. Sweepback and forth to get a feel for the target, keeping the searchcoil close to the ground. Now,continue to sweep back and forth as you slowly raise the searchcoil higher and higher. If theresponse diminishes quickly and never gets very broad, the target is probably a coin. If theresponse diminishes slowly as you lift the searchcoil, and you get a broad response, the targetis probably an aluminum can. If you practice this by laying a coin and a flattened aluminum canon the ground, you will quickly understand how to differentiate the two and you will probablynever have to dig another aluminum can. And, you will know whether it was deep or shallow.This technique works well in the All Metal modes, 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 responsethan objects of similar size with irregular shapes. The easiest way to demonstrate this is with analuminum screwcap from a soda bottle. In its normal shape, it occupies a volume, and gives asomewhat broader response than that of a coin. But if you flatten it, the response will be crisper andmore like that of a coin. Again, these differences are most readily noticed in the All Metal modes. Long skinny iron or steel objects such as nails usually produce a double response when scannedlengthwise, and a weaker single response when scanned crossways. This is most noticeable inthe Motion All Metal mode. However, a coin lying on its edge can produce a similar response, sorely on both the target ID as well as target feel to distinguish between different kinds of objects.Objects within 2 to 3 inches of the searchcoil will often produce multiple responses as you sweepacross them, because the response field close to the searchcoil is irregular.Estimating Target I.D. With a single sweep over a target, you will usually see a 2-digit target ID displayed on the LCD.Repeated sweeps back and forth over the target may cause the 2-digit target ID values to changewith each sweep of the coil; this may seem inconsistent with your discrimination setting. Thesevariations and inconsistencies provide important clues regarding the identity of the buried object.Most metal detectors have difficulty properly identifying steel bottle caps, and the F75 is noexception. Steel bottle caps will often read in the coin range, at the high end of the scale.The ID number you receive from a buried coin will usually be consistent regardless of sweepspeed or angle. The readings from a steel bottle cap will tend to bounce around a lot more,especially with variations in sweep speed or angle. By paying attention and taking this intoaccount, you can minimize the number of bottle caps you dig.The information provided by the Visual Target ID may be different than the detector’s AudioFeedback because the visual and audio systems are independent of one another. The internalsignals and algorithms controlling the Visual and Audio output are different. Therefore whatyou hear, or do not hear, provides additional information regarding target ID. For instance, ifdiscrimination is set at 12, and most sweeps result in no visual target ID, the target is most likelyiron even though the majority of the ID numbers will be greater than 12.The F75 has a tendency to up-average nonferrous targets in the proximity of iron, indicating IDnumbers higher than would be obtained in an air test. This tendency is connected with theF75’s enhanced see-through ability – that is, the ability to find valuable targets in an areawhere there is a lot of iron trash.F75-MANUAL(122811).qx 12/14/12 9:04 AM Page 13 14 31F75Comprehensive Operating Manual & Guide to Metal Detecting Comprehensive Operating Manual & Guide to Metal DetectingF75 Note: FASTGRAB willnot automaticallybalance over highlyconductive soils, such asa wet salt water beach.Search TechniquesSweeping Searchcoil (this does not apply toPinpointing with the trigger switch) Keep thesearchcoil in motion to detect targets. Sweepthe searchcoil parallel to the ground; do not liftthe searchcoil at the end of the sweep.When you have located a target and continuesweeping back and forth for verification, usebroad, deliberate sweeps across the target forthe most accurate target ID. Do not use shortsweeps as you might with other metal detectors.Shallow Targets Shallow targets tend to give multipleresponses, with the last response being theone that remains illuminated on the visualdisplay. This last response is usually sampledat the edge of the searchcoil and will tend to be inaccurate. If you suspect a shallow target(within 2 to 3 inches of the searchcoil), lift the searchcoil slightly, and slow down your sweepspeed until you notice a single response consistently in the same place. Large shallow targets can cause signal overload, indicated by the siren sound. In these instances,raise the searchcoil until the overload warning disappears, and sweep at this increased height.Large Targets If an overload warning is not confined to a small spot, you are probably overloading on a largeobject, for example, a large iron pipe, reinforcing steel in concrete, or buried sheet metal. It isusually not possible to locate objects, such as coins, in close proximity to large masses of metal.Pinpointing With the Trigger SwitchWhen you turn the F75 on, the ground balance setting is preset to give a positive response onnearly all soils. This means that if you are pulling the pinpoint trigger, the audio tone will getlouder as you lower the searchcoil to the ground. But you do not want to hear the ground; youjust want to hear the target. So always Ground Balance first.After you have discovered a buried metal target using the ALL METAL or DISCRIMINATIONModes, use the trigger switch to pinpoint its exact location.Position the searchcoil an inch or two (2.5-5cm) above the ground, and to the side of thetarget. Then pull the trigger. Now move the searchcoil slowly across the target, and the soundwill indicate the target’s location. As you sweep from side to side, and hear no sound at theends of the sweep, the target is located in the middle of that zone, where the sound is loudestand the audio pitch is highest. If the sound is loud over a wide area, the buried object is large.Use the PinPoint feature to trace an outline of such large objects.Estimating Target SIZE, DEPTH, and SHAPEWhen the trigger is pulled to activate Pinpoint, the LCD displays estimated depth. Theestimate is based on the presumption that it is a coin-sized target. WRONGRIGHTF75-MANUAL(122811).qx 12/14/12 9:04 AM Page 14 Ground BalancingWhat is Ground Balancing?All soils contain minerals. Signals from ground minerals are often tens or hundreds of timesas strong as the signal from a buried metal object. The magnetism of iron minerals, found innearly all soils, causes one type of interfering signal. Dissolved mineral salts, found in somesoils, are electrically conductive, causing another type of interfering signal.Ground Balancing is the process by which the metal detector cancels the unwanted groundsignals while leaving signals from buried metal objects intact. This is accomplished byestablishing the detector’s internal Ground Balance setting; this setting is calibrated to the soiland eliminates the signal produced by ground minerals.Calibration to the actual soil condition will result in deeper target detection and quieteroperation. This calibration, or Ground Balancing, can be accomplishedautomatically with the detector’s internal computer, by pushing theTrigger Switch forward, or manually in the All Metal menu.The ground balance setting carries through into all operating modes. InDiscrimination mode, the ground signal is generally inaudible unlessthe discrimination setting is 0.AUTOMATIC GROUND BALANCING PROCEDURE (FASTGRAB™)1. Find a spot of ground where there is no metal present.2. Hold the detector with the searchcoil about one footabove the ground.3. Push the TRIGGER SWITCH forward with your index finger.4. Physically pump the searchcoil and detector up anddown over the ground.Lift it about 6 inches above the ground and lower it to within 1inch of the ground, about once or twice a second. 5. A 2-digit value will appear on the display. This isthe Ground Balance setting.If the detector’s internal computer is unable toground balance, an error message will appear:• If the message OVERLOAD RAISE COIL – CAN’T GBappears, you will also hear a siren sound.You are probably over metal.• If the message CAN’T GB appears, you may not bepumping the coil, or you may be over a small pieceof metal.30 15F75Comprehensive Operating Manual & Guide to Metal Detecting Comprehensive Operating Manual & Guide to Metal DetectingGround Balancing (continued)G.H. PHASE 90GC PHASE 90STEEL BOTTLE CAPS & FLAT IRON TRASH Modern motion-type target ID metal detectors usually have difficulty consistently identifyingsteel bottle caps and other flat iron trash objects. Double-D searchcoils also have a reputationfor having difficulty distinguishing steel bottle caps from coins, and for being unable toeliminate steel bottle caps from detection. If you are searching in an area where there aremany steel bottle caps or other flat iron trash targets, minimize the amount of unnecessarydigging with the following methods:1. SEARCH WITH THE bc (BOTTLE CAP) PROCESS using the PROCESS # feature.This method calculates visual ID differently in order to cause steel bottle caps to readlower on the scale, and to register less consistently. A desirable object such as a coinwill usually produce numeric values that are fairly consistent in both directions ofsweep. See PROCESS # under the DISCRIMINATION Mode section of this manual.2. SEARCH WITH THE dP PROCESS. This method calculates visual ID differently inorder to cause steel bottle caps to ID lower on the scale and to register lessconsistently. It also produces more audio clues to the character of the target.3. LIFT THE SEARCHCOIL. Within 2 inches of a Bi-Axial searchcoil, the crossed magneticfields of the Double-D construction can produce anomalous responses. If the object feelsshallow (strong signal, narrow response, or multiple responses in a single sweep) and isgiving consistent high readings like a coin, raise the searchcoil 2 to 3 inches and try again.A coin will almost always continue to give consistent readings unless it is right next to aniron object. A steel bottle cap that is at least 3 inches away from the searchcoil willusually produce readings that bounce around from medium to low numbers. 4. SWEEP THE REAR OF THE SEARCHCOIL OVER THE CENTER OF THE TARGET,OR SWEEP RAPIDLY.a. If the ID# is repeatable in the range of 68 to 72, when passing thecenter of the searchcoil over the target at a normal speed, then thetarget is probably a dime or copper penny.b. If the ID# is not in the range of 68 to 72 then:i. Sweep the back end of the searchcoil over the target. If toneschange from high to low, the target is probably a bottle cap.ii. Sweep the center of the searchcoil rapidly across the target.1. If tone and ID# drop, it is probably a bottle cap.2. If a bottle cap, then the faster you sweep, thelower the tone.5. USE THE CONFIDENCE INDICATORCoins will usually produce a highconfidence level, whereas steel bottle capsand other trash will usually indicate a low orerratic confidence, even if the ID numbersare consistently in the range of a coin.Confidence level is useful even if notusing the dP or 3b processes.Capabilities And Limitations (continued)Sweep back endof searchcoil oversuspected bottle cap.(Low Tone = Bottle Cap)F75-MANUAL(122811).qx 12/14/12 9:04 AM Page 15F75MANUAL GROUND BALANCINGIn most situations, it is preferable to push the trigger switch to activate FASTGRAB automaticground balancing. Generally, it is best to first let the computer automatically cancelinterference from ground minerals. However, for gold prospecting, searching on a wetsaltwater beach, or searching in an area with so much metal trash that there is no cleanground for the computer to sample, we recommended that you manually ground balance.Manual ground balancing requires a bit of skill, acquired with some practice. The range of ground balance settings indicated on the display range from 0 to 99; however,each displayed number spans 5 detent steps on the settings knob. The actual internal groundbalance settings change with each step; there are a total of 500 different settings. Under someground conditions you may be able to hear the individual steps in the setting.The Fe3O4 bar graph on the LCD display indicates the amount of magnetic mineralization. Thesearchcoil must be in motion to measure Fe3O4. The most accurate measurement is obtainedby pumping the searchcoil, as in the Ground Balancing procedure.The two-digit G.B. Setting number displayed on the LCD indicates the type of groundmineralization. Some typical ground mineralization types are:0 – 10 Wet salt and alkali5 – 25 Metallic iron. Very few soils in this range. You are probably over metal.26–39 Very few soils in this range -- occasionally some saltwater beaches40–75 Red, yellow, and brown iron-bearing clay minerals75–95 Magnetite and other black iron mineralsWhen manually ground balancing, try to “feel out” a spot on the ground to make sure there isno metal present. In order to avoid locking onto metal, the computer will not balance toground where the GB setting is less than 40. Where the ground reads less than 40, manualground balancing is required.To perform the Manual Ground Balancingoperation, do the following:1. Select the MANUAL G.B. functionThe legend G.B. SETTING appears.The present ground balance settingis displayed (0-99).The message PUMP COIL TO G.B.will appear.2. Physically pump the searchcoil anddetector up and down over theground.Lift it about 6 inches above theground and lower it to within 1 inchof the ground, about once or twice asecond.16 29F75Comprehensive Operating Manual & Guide to Metal Detecting Comprehensive Operating Manual & Guide to Metal DetectingGround Balancing (continued)GROUND BALANCINGTo achieve maximum depth in any detection mode, as well as when using the PinPointfeature, the F75 offers the ability to cancel out ground minerals either by manual adjustment,or automatically using the FASTGRAB feature.If you do not perform the ground balancing operation, the Discrimination mode will usually stillwork fairly well, but the ALL METAL modes will not. The Pinpoint feature can be used forpinpointing objects at moderate depth in most soils without prior ground-balancing.The internal computer will not cancel salt water, so when detecting on wet ocean beaches,ground balancing must be done manually.DISCRIMINATIONDiscrimination refers to a metal detector's ability to ignore metal objects in selected categories,especially iron and aluminum. This makes searching much more pleasant in an area with a lotof metal trash. The F75 offers a wide variety of discrimination features which you can selectaccording to the search conditions and your personal preference.DEPTH READINGThe estimated Depth Reading displayed when pulling the PinPoint toggle is based on thestrength of the signal. It is calibrated to coin-sized objects. Smaller objects will read deeperthan they actually are, and large objects will read shallower than they actually are.AIR TESTINGThere may be times when you want to test or demonstrate the metal detector without sweeping it overthe ground, for instance, if not fully assembled, or if you are indoors. To air test, place the searchcoil ina spot where the detector is stable and more than two feet away from any large masses of metal,including the reinforcing steel usually present in concrete. If you are wearing a wristwatch or jewelryon your hand or arm, remove it. Then, test or demonstrate by waving metal objects over thesearchcoil; wave objects briskly, several inches over the top of, and parallel to, the searchcoil.Ground balancing cannot be tested or demonstrated in air unless you happen to haveappropriate specimens of iron minerals available.SWEEP SPEED The F75 is noted for its quick response. This gives it unsurpassed ability to locate and identifygood targets surrounded by trash. It also permits the user to sweep the searchcoil quickly inorder to cover more ground with very little risk of losing targets. In general, if you aresearching an area where the desirable targets are more than 8 to 10 inches deep, a fastersweep speed will detect to a greater depth and yield more accurate target IDs. CHECKING A TARGETIn order to most accurately verify a detected target with most other metal detectors, users willnarrow their sweep and loiter over the top of the target. The F75 is different. The F75's quickresponse and advanced signal sampling system produces the most accurate target IDs withdeliberate (shoulder width) sweeps all the way across the target, even if there are othertargets nearby. If you check targets using sweep techniques learned on some other detectors,you run the risk of getting less accurate target IDs. You can use the confidence level indicatorto improve your technique.Capabilities And Limitations (continued)F75-MANUAL(122811).qx 12/14/12 9:04 AM Page 16 F753. Turn the SETTINGS KNOB to adjust the setting.The goal is to eliminate the sound as the coil is being pumped over the ground. Insome soils, the sound is not completely eliminated.If the ground balance adjustment is incorrect, there will be a difference in the sound as thesearchcoil is either moving toward or away from the ground. It sounds like you are eitherpulling the sound out of the ground, or pushing the sound into the ground.• If the sound is louder as you raise the searchcoil, increase the ground balance setting.• If the sound is louder as you lower the searchcoil, reduce the ground balance setting.NOTE: Experienced users often prefer to adjust the ground balance to get a weak but audibleresponse when lowering the searchcoil. This is called adjusting for positive response. Positive and Negative Response The purpose of ground balancing is to adjust the metal detector to ignore ground minerals. Ifthe setting is incorrect, ground minerals will give either a positive or a negative response,depending on which direction the adjustment is off.POSITIVE RESPONSEIf the G.B. setting is too high a number, the response of minerals will be positive. This meansthat when the searchcoil is lowered to the ground in PinPoint, Stat, or Motion All Metal mode,the sound will get louder as the searchcoil approaches the ground. The sound will growquieter as the searchcoil is raised. What, if anything, you will hear in discrimination modedepends on the discrimination setting.When searching in an All Metal mode, if ground balance is properly set to cancel the ground,and you sweep over a positive hot rock, the rock will give a “zip” sound similar to that of ametal object. NEGATIVE RESPONSEIf the G.B. setting is too low a number, the response of minerals will be negative. When thesearchcoil is lowered to the ground in PinPoint, Stat, or Motion All Metal mode, the machinewill be silent. The machine will sound off as the searchcoil is lifted away from the ground.What, if anything, you hear in discrimination mode depends on the discrimination setting.When searching in Motion All Metal mode, a negative hot rock will produce a “boing” soundafter passing over it, making it difficult to know where it is located. It will not have the soundand “feel” of a metal object.28 17F75Comprehensive Operating Manual & Guide to Metal Detecting Comprehensive Operating Manual & Guide to Metal DetectingF75Motion All Metal ModeThe Motion All Metal mode is more sensitive and offers better feel than the Discriminationmode, and is used to find all metal objects present in the ground. The searchcoil must be inmotion for objects to be detected. This is a single filter search mode similar to the “fastautotune”, “SAT”, or “P4” modes found in other detectors you might already be familiar with.THRESHOLD: Adjustable from -9 to +9. For maximum ability to hear the weakest signals,adjust this background noise level high enough so that it is barely audible while the detector isin use in the field. To eliminate the weakest signals, adjust into the negative region, which willallow the machine to run silently if the Sensitivity is not set too high.The threshold level changes slightly with each detent step on the SETTINGS knob. Eachnumber on the numeric readout corresponds to five steps.AUDIO PITCH This control allows you to change the range of frequencies that you hear.Values range from -9 to 9; 0 is default. Negative numbers lower the frequency of the tone youhear; positive numbers raise the frequency. This feature is intended to make the tone morepleasant to your ear; choose your personal preference. Users who have suffered somehearing loss, (including the natural loss of ability to detect high and low frequencies with age)may find this control helpful.SENSITIVITY This controls the signal gain, and is adjustable from 1 to 99. In the presenceof electrical interference, high ground mineralization, or variable ground mineralization,operation will usually be too noisy (wobbly and erratic sound) if the sensitivity is set too high.At settings above 90, the internal circuit noise of the machine will probably be audible.The sensitivity level setting is largely a matter of personal preference. However, if you cannothear at least some noise, the smallest or deepest objects will not be detected.The sensitivity system has two stages, 1-29 (low gain), and 30-99 (high gain). As youdecrease sensitivity and cross the transition from 30 to 29, you may notice that thebackground noise increases. Despite this increase as you decrease sensitivity to the lowersetting, 29, the sensitivity is in fact lower under 30, and the machine is less susceptible tooverload from large targets, ground minerals, and salt water. You may need to adjust to asetting of 29 or less to silence electrical interference, or to prevent overload on highlymineralized ground or in salt water. You may also notice a shift in the ground balance settingover difficult ground conditions as you cross this transition. MANUAL GROUND BALANCE Manual Ground Balance can only be performed while in an All Metal mode, but the resultantsetting will carry over if you change into Discrimination mode. See the previous section onGround Balancing for instructions on how to use this feature.We suggest that you manually ground balance using only the MOTION All Metal Mode. Theresult will be more accurate than when using STAT All Metal Mode.Capabilities And LimitationsDEPTH The F75 can detect U.S. coins to a depth of up to 15-16 inches (37-40cm) under goodconditions. Large objects (55 gallon drums, manhole covers, etc.) can be detected to a depthof up to several feet (1-2 meters). Electrical interference from power lines and from electrical appliances and electronicequipment can reduce detection depth, or cause audible interference, making it necessary forthe user to reduce the sensitivity setting. Soils with large amounts of iron or salt mineralsmay also reduce detection depth or necessitate a reduction in the sensitivity setting. TARGET IDENTIFICATIONThe F75 identifies the probable type of metal object by measuring its effective electricalconductivity, which is displayed as a number from 0 to 99 on the LCD screen. The effectiveelectrical conductivity of an object depends on its metallic composition, size, shape, andorientation relative to the searchcoil. Since coins are minted to tightly controlled specifications,they can be accurately identified. Identification of pull-tabs and foil is less consistent becausethese kinds of targets come in wide variety. In general, smaller objects, and objects madefrom lower conductivity alloys such as iron, bronze, brass, lead, pewter, and zinc will readlower on the effective conductivity scale. Larger objects and objects made from higherconductivity alloys such as silver, copper, and aluminum, will tend to read higher. The notableexceptions are gold, which usually reads low because it is rarely found in large pieces, andzinc pennies, which read moderately high because of their size and shape. Although nails andother iron and steel objects will usually give low readings, ring-shaped pieces of iron (forinstance steel washers and harness rings) will usually produce medium to high readings. Flatpieces of iron or steel, such as can lids, will occasionally do the same.Most targets can be identified accurately in air to a distance of about 10 inches. The mineralsin many soils will cause identification to be less accurate. In most soils, effective targetidentification can be had to a depth of at least 8 inches. REQUIREMENT FOR MOTION: PINPOINT FEATURE As with other modern metal detectors, the F75’s searchcoil must be kept in motion in order toboth detect and identify targets. The All Metal modes are more forgiving of sweep speedvariation than is the Discrimination mode.The trigger-activated PinPoint feature continues to detect metal if searchcoil motion stops overthe target. The PinPoint feature is used primarily to pinpoint the exact location of a target sothat it can be retrieved with a minimum of digging, and does not provide target identification. F75-MANUAL(122811).qx 12/14/12 9:04 AM Page 17 18 27F75Comprehensive Operating Manual & Guide to Metal Detecting Comprehensive Operating Manual & Guide to Metal DetectingF75Static All Metal ModeThis mode is useful for finding large, deep objects, i.e. larger than a coin and deeper than 12inches (30cm). STATIC functions similar to PinPoint but occupies a different position on theuser interface. The audio signal gets stronger as the searchcoil approaches the ground. Unlikethe other modes, the detection sound will not disappear if you stop moving the searchcoil.The four adjustments are performed the same as with MOTION All Metal Mode, as describedon the preceding page.THRESHOLDThe audio threshold in the STATIC mode is internally fixed and cannot be adjusted by the user. Retuning: The audio threshold will slowly drift when searching in this mode. If you movequickly between temperature environments, such as from shade to sun, audio thresholdmay drift more rapidly until the searchcoil temperature stabilizes. When the audiothreshold drifts in this fashion, pull the trigger back momentarily to retune the detector.You will need to retune periodically when searching in this mode.AUDIO PITCHWorks the same as in MOTION mode; see previous page.SENSITIVITYSet the sensitivity high enough too hear some random background noise and/or a slightamount of ground response. If you do not hear these noises, you will sacrifice detection depth.If the background chatter is too annoying, or the ground noise is so high that it impedesoperation, reduce sensitivity. Such a downward adjustment in sensitivity improves depthdetection as you can now hear weak signals better.The sensitivity system has two stages, 1-29 (low gain), and 30-99 (high gain). As you lowersensitivity and cross the transition from 30 to 29 in STATIC mode, it may be necessary toretune by pulling the trigger switch momentarily. You may need to adjust to a setting of 29 orless to silence electrical interference, or to prevent overload on highly mineralized ground or insalt water. You may also notice a shift in the ground balance setting over difficult groundconditions as you cross this transition. GROUND BALANCEAlways perform the ground balance procedure before searching in STAT mode, using thetrigger or with the manual adjustment.If you do not ground balance before searching in STAT mode, most ground will produce anaudible tone as you lower the searchcoil; the ground will “sound off.” Some soils will notsound off, but will remain quiet with a loss of sensitivity.DEPTH DISPLAYTo see a target’s depth, in inches, pull the toggle switch.TARGET IDMove coil back-and-forth over target to see visual target ID.Frequency ShiftingOne disadvantage of a highly sensitive metal detector is its susceptibility to electricalinterference from other electronic devices. If the detector chatters while the searchcoil is notin motion, the cause is either electrical interference or internal circuit noise due to a highsensitivity setting. If the detector chatters or emits intermittent false signals in the field, youare also probably experiencing electrical interference. If you suspect electrical interference,you may change the F75’s operating frequency. This is a trial and error method to try to find afrequency different from the suspected source.To shift frequencies:1. Hold the MENU button down. Do not release the button.2. Push the trigger forwardOR pull the trigger back to change the frequency.Each frequency change requires a push of the MENU button.Each actuation will shift the frequency by one value.The LCD will display the frequency, from F1 to F4. F1 is the lowest frequency. And the defaultfrequency. The F75 does not retain changes in the frequency setting, when powered off.See the Search Techniques section of this manual for more information on electricalinterference.F75-MANUAL(122811).qx 12/14/12 9:04 AM Page 18 26 19F75Comprehensive Operating Manual & Guide to Metal Detecting Comprehensive Operating Manual & Guide to Metal DetectingF75LCD Visual Display (continued)BATTERY CONDITION INDICATORFresh alkaline batteries will illuminate all three bars. When no bars are displayed and thebatteries are about to go dead, the BATT legend will start flashing. The detector should operatefor an additional 30 minutes from the time the BATT legend starts flashing. If using NiMHrechargeable batteries, the display will remain stuck on the second or third bar for most of thebattery life; when it drops to the first bar, the batteries will go dead within several minutes.G.B.This is the ground balance setting, 0-99. It is displayed when in the Manual G.B. menusetting, or when the trigger is pushed for FASTGRAB computer-assisted ground balancing.SETTING This is illuminated when you are in the menu. When the word “SETTING” is indicated, thenumber being displayed is a setting, and not, for instance, a Target ID indication.MESSAGES The small rectangular box at the bottom-center of the LCD displays advisory messages.If a metal object or highly magnetic soil is so close to the searchcoil that the signal isoverloading the circuit, the message OVERLOAD - RAISE COIL will appear.Such overloads will not harm the detector, but the detector will not detect metals properlyunder these conditions. Raise the coil until the message disappears; the siren sound will alsostop. Resume normal detection.The message RAISE COIL only appears when using the bc process, accessed through thePROCESS # menu selection. This message indicates the presence of a target which may betoo close to the searchcoil to be accurately identified. For better target identification, sweepthe searchcoil farther away from the surface of the ground.The message PUMP COIL TO GB will appear when you push the trigger forward to groundbalance. See the Ground Balance section of this manual for instructions. The message CAN’T GB can only appear when the trigger is pushed forward, invokingFASTGRAB automatic ground balancing. This message appears when the detector is unableto measure the soil in a manner suitable for ground balancing. This message is usually theresult of the presence of metal. Try another spot to find an area free of metal.BACK LIGHTThe LCD is back-lighted for use in low light and dark conditions.The backlight is always illuminated, but the illumination is usually not evident in daylight.You cannot turn the backlight off. The single high-efficiency light emitting diode providing theillumination is a low current device, and has a negligible impact on battery life. F75-MANUAL(122811).qx 12/14/12 9:04 AM Page 19 Discrimination ModeThe Discrimination Mode is used to eliminate trash metal objects from detection, e.g. nails,aluminum foil, or pull-tabs. The searchcoil must be in motion for metal objects to be detected.Discrimination incurs some loss of sensitivity to small or deep objects.The F75 discrimination system is much improved over conventional discrimination systems,and may function quite differently than other discriminators you may be accustomed to. Inolder systems, the apparent sensitivity decreases as discrimination level increases. The F75’ssensitivity may increase as discrimination increases, depending on the process number andnotches being used. Therefore, do not use the discriminator to control sensitivity. First set thediscrimination level and notches to establish objects to detect or eliminate; then adjustsensitivity downward to eliminate interference, or upward to “work into the noise,” if preferred.SENSITIVITYThis controls the signal gain, and is adjustable from 1 to 99. Unlike the All Metal modes, theDiscrimination mode is designed to operate silently. If you hear noise when there is no metalpresent or when the searchcoil is not in motion, reduce the Sensitivity setting until the machinegoes quiet. NOTE: There is no interaction between the sensitivity settings of the All Metaland Discrimination Modes.The sensitivity system has two stages, 1-29 (low gain), and 30-99 (high gain). As you lowersensitivity and cross the transition from 30 to 29, you may notice the background noiseincrease. You may need to adjust to a setting of 29 or less to silence electrical interference, orto prevent overload on highly mineralized ground or in salt water. You may also notice a shiftin the ground balance setting over difficult ground conditions as you cross this transition.DISCRIMINATION LEVELThis is adjustable from 0 to 65, and controls the range of objects to be eliminated fromdetection (discriminated out or rejected). Objects with numeric values below the selecteddiscrimination level will not be detected. NOTE: The numerical range that pertains to eachclass of object is printed at the top of the visual display. To eliminate iron, a setting of 15 isusually about right. A setting of 65 will eliminate aluminum trash and zinc pennies, but nickelswill also be lost, unless you notch-in nickels with the NOTCH feature. To use DISC LEVEL1. Highlight DISC LEVEL using the MENU button.2. Rotate the SETTINGS knob.As you rotate the knob, a number between 0 and 65 appears.3. Press MENU when you reach the desired target discrimination value.• If you do not press MENU, and let the display time-out, the last displayed valuewill be stored as the discrimination value.• All targets, up to and including the value selected, will be eliminated fromdetection, unless notched-in.5. A slash will appear over the target words being eliminated. Notice that two slashescan appear over each word. The left slash represents the bottom half of the range; theright slash represents the top half of the range. When you select a value within anyrange, the slash will appear, even though all values within that range might not beeliminated from detection. To recall the discrimination setting, press the MENU buttonuntil you enter the DISC LEVEL feature.20 25F75Comprehensive Operating Manual & Guide to Metal Detecting Comprehensive Operating Manual & Guide to Metal DetectingF75NOTCH Unlike Discrimination Level, which eliminates all targets from the left of the scale to the right,NOTCH can eliminate and re-include targets within the scale displayed at the top of thedisplay. Inclusion or exclusion of target ranges is indicated with a half-crossed or crossed icon.To demonstrate how to set a notch, follow this instruction at first use.1. Reset all detector values to default: a. turn detector offb. press-and-hold red MENU button and push-forward-and-hold Toggle Switchc. turn detector on while continuing to hold MENU and Toggled. release Menu and Toggle.2. Press MENU button 4 times to move down to the NOTCH feature-then rotate the SETTINGS knob to the right until the number 40 appears.-then press MENU again to accept this notch value.3. Notice that a thin line appears across the word “TAB” printed on the top of the display.4. Press MENU again to exit the NOTCH feature.5. Targets in the first 1/2 of the TAB range (TAB range is from 36 to 55) will be eliminatedfrom detection.6. A half-slash will be permanently displayed across the top-left of the word “TAB.”NOTCH allows you to select target ranges equal to 1/2 of each category for inclusion orexclusion from detection. As you rotate the knob, the target indicator will appear above therange currently selected. If you set the notch value anywhere within the range, the notch valuewill not necessarily stop at this number, notch ranges are fixed as follows:1. 1-7 iron 6. 31-35 nickel2. 8-15 iron 7. 36-45 tab3. 16-20 foil 8. 46-55 tab4. 21-25 foil 9. 56-60 zinc5. 26-30 nickel 10. 61-65 zincThe following are characteristics of NOTCH programming:• As you rotate the knob to enter a notch range, the target indicator block at the topedge of the screen illuminates to show you the range you are in.• After you have selected a notch, a slash is illuminated over that range, indicating thatall targets within that range (see chart above)are eliminated from detection.• When you enter the program to make achange to the notch settings, you arechanging the status of the notch. If noslash is illuminated and you press MENU toset a notch range, you will be notching-out thisrange. If a slash was previously illuminatedand you press MENU to set this notch range,you will be notching-in this range.• Programming a notch range alwaysreverses the status of the notch.Discrimination Mode (continued) LCD Visual Display (continued)Since different metal objects can produce similar signals, and since minerals in the soil candistort the signals, the probable target ID's are just that -- probable. There is no way ofknowing for sure what's buried other than to dig it up. Experienced metal detector users havea rule of thumb -- "when in doubt, dig". DEPTH When the trigger is pulled to facilitate pinpointing an object, the 2-digit numerical displayindicates the approximate depth of the object, in inches, based on the assumption that theobject is a typical U.S. coin. Small objects will read deeper than they actually are, and largeobjects will usually read shallower than they actually are.The DEPTH bar graph on the left of the display divides target depth into shallow, medium, anddeep. This depth range appears while searching, and is less accurate than the value derivedusing the pinpoint toggle switch.Bar graph ranges for a coin-sized object are Shallow (0-4inches), Medium (4-8inches), andDeep (8inches +).CONF (Target Confidence Indicator)This 6-segment graphic indicates how confident the detector is of the 2-digit targetidentification it has assigned. If all 6 segments are displayed, you can be confident that thetarget ID is accurate. If 3 or fewer segments are displayed, the confidence is very low.Junk targets tend to produce lower confidence indications than coin targets of similar electricalconductivity. Sloppy sweep technique also reduces the confidence indication. You can usethis indicator to train yourself to sweep more skillfully.Fe3O4 BAR GRAPH (magnetite)This bar graph displays the magnetic mineralization factor, or magnetic susceptibility, of the soil.Magnetic susceptibility is expressed in terms of the percent volume of the iron mineral magnetite,which most black sand is made of. The depth to which objects can be accurately identified isstrongly influenced by the magnetic susceptibility of the soil. High Fe3O4 values have a greatereffect on detection depth in the Discrimination mode than in the All Metal mode. For the mostaccurate Fe3O4 reading, pump the searchcoil as though you were ground balancing.Fe3O4 approx.Range micro-cgs Description3 7,500 uncommon but not rare, heavy mineralization1 2,500 heavy mineralization, not uncommon in goldfields0.3 750 heavy mineralization, but not uncommon in some regions0.1 250 medium mineralization, typical0.03 75 light mineralization, but common0.01 25 light mineralization, your G. B setting may also be lowblank <14 quartz & coral white beach sandsF75-MANUAL(122811).qx 12/14/12 9:04 AM Page 20 24 21F75Comprehensive Operating Manual & Guide to Metal Detecting Comprehensive Operating Manual & Guide to Metal DetectingF75Using DISC LEVEL in conjunction with NOTCH gives you a great deal of flexibility in decidingwhich values to include or exclude from detection. Beware that this combination can beconfusing.Here are some examples of NOTCH used in conjunction with DISC LEVELIf Discrimination Level is set at 60, and you set the top-of-foil (21-25) notch between 21and 25, then: top-of-foil range (21-25) is NOTCHED-IN (i.e. detected)If Discrimination Level is set at 23, and you set the top-of-foil (21-25) notch between 21and 25, then: 21, 22, & 23 are NOTCHED-IN. 24 & 25 are NOTCHED-OUTIf Discrimination Level is set at 15, and you set the top-of-foil (21-25) notch between 21and 25, then: 21-25 are NOTCHED-OUTNUMBER OF TONES (# OF TONES)This menu selection allows you to select the number of audio tones emitted by the detector.Different search conditions, search objectives, or personal preference will determine howmany tones you want to hear. With the below settings, you can decide to hear the same tone,regardless of the target category, or have different categories of targets induce different tones.The “# OF TONES” selections are:1: SINGLE MEDIUM PITCH TONE.All types of metal induce the same tone.1F: MEDIUM-TO-HIGH PITCH TONE varying in proportion to target signal strength.Large shallow objects will produce a squeal. The variable audio pitch provides you moreinformation about the detected object, but some people find the sound on strong signalstoo annoying. 2F: TWO TONES.Similar to 1F, except that iron produces a low-pitched tone regardless signal strength.Useful if you want to hear al