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Ethics and the art of recovery

*reprinted with permission of First Texas Products*

First Texas Products takes pride in the industry we serve, and ask you to join us in observing and promoting ethical and legal detecting practices, and in supporting dealers and organizations that do the same.

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Discrimination Mode "Sensitivity" and "Depth" in Single-Frequency VLF Metal Detectors

*Used with permission of Fisher Labs*

Dave Johnson, Chief Designer @ FTP & Fisher

Some metal detectors are “more sensitive” than others, and “how deep” a particular metal detector can detect a specific metal object depends on many variables.

“Air test sensitivity” refers to the maximum repeatable detection distance achievable in air using a standard metal test piece (typically a US nickel coin), with the searchcoil that’s standard with that model, in a location without electrical interference, the machine adjusted to just barely eliminate background chatter. If ground balancing is available on the machine, it must be done using ferrite. …….. A properly done “air test” provides an indication of a machine’s potential to “go deep” on buried coins. Because of interference from magnetic iron minerals in the ground, actual detection depth will usually be much less than what’s achieved in “air test”. (NOTE: for maximum depth on buried objects, search in the all-metals ground balanced mode, which is much less affected by iron minerals.)

“Sensitivity control” A control labeled “sensitivity”. It actually controls either gain or threshold, or a combination of both, depending on the machine. If both, the higher settings vary threshold and the lower settings vary gain.

“[Audio] threshold control” Determines the signal strength level corresponding to the threshold of audibility. A negative threshold setting is used to suppress signals by a fixed amount so that only signals stronger than that amount will be heard. Negative threshold settings are used to silence internal “circuit noise” and electrical interference. Machines which have no threshold control have an internal threshold which allows silent operation, or a control labeled “sensitivity” which actually controls threshold. …..Some models allow positive threshold settings. In most cases the positive range controls the loudness of a minimum detectable signal, a separate internal threshold determining what will or will not be detected.

“Gain control” This makes signals bigger or smaller. High gain settings make signals bigger, and therefore signals which were originally weaker can more easily exceed the audio threshold, and be heard. If the gain setting is too high, electrical interference or internal circuit noise may cause constant audio chatter. ….Lower gain settings reduce the size of signals, so that relatively weak unwanted signals (electrical interference, deep iron fragments, aluminum foil shreds, etc.) can be silenced.

The effects of discrimination “Discrimination” between different metal objects is done using a different set of signals than the ones used for detection. Since the overall purpose of discrimination is to eliminate response to certain classes of metal objects beginning with metallic iron, magnetic iron minerals in the ground will tend to make nonferrous metal signals look more like ferrous, increasing the probability of their being rejected by the discrimination circuit. Some machines provide data on the amount of iron mineralization, so with experience you can estimate the depth of effective detection and discrimination on that site.

Interactions between controls There are many types of discriminators, all of which have some effect on “air test sensitivity”. The most common pattern (nearly universal in older all-analog machines) is that “air test sensitivity” decreases slightly as discrimination is increased. Most of our recent designs do discrimination entirely in software, where control settings are actually data which don’t necessarily do the same things to signals that circuit components used to do. In the case of the T2 and F75, those differences were confusing to some users. In general if a T2 or F75 seems too noisy, the solution is to set the discrimination level to the iron range; and if that doesn’t do the job, also reduce the sensitivity setting. In the F70 and F5 which are more recent designs, the interactions between control settings and signals are even more complex, but we did a better job of hiding the details thereby giving the user an improved sense of predictability.

Electrical interference In many (probably most) machines, elimination of electrical interference is best achieved by setting the discrimination level to the top of the iron rejection range, then reducing the threshold setting (if threshold control is available; it may be labeled “sensitivity”). Even if the machine chatters in air, while actually in motion searching over the ground it will usually quiet down, except for occasional random pops which don’t sound like targets. (Frequency shifters found on some machines are beyond the scope of this essay.)

How much depth should I get? There is no single answer to that question. In a few places, you may get in-ground depth almost as good as in an air test. There are also a few places with so much iron or salt mineralization that most detectors are not even usable. In most soils, the best discriminators will usually detect coins to a depth of 7 inches or more, and will usually provide usable discrimination and target ID to a depth of 5 inches or more. However, a particular target may not be detected or may be misidentified because of the proximity of rocks or other metal targets, disturbed soil caused by digging, peculiarities of the target, or suboptimal user technique for that target in that setting. On sites where the discriminator doesn’t provide enough depth for your purposes, search in the all-metals ground balanced mode if the machine provides one.

Copyright First Texas Products and Fisher Labs File: sensitivity and depth last update 18 Sept 08

What Kind of Detector Should I Buy?

That’s a goooood question! There are lots of people who have been in the hobby for many years who still try different machines on a steady basis. (I’m one of them 🙂 ) There are others who have found a detector they are comfortable with, and have stuck with it, having no desire to change. That’s fine too!

If you’re a person considering getting into this great hobby, I suggest finding someone who already has a metal detector and asking them if you can try it. If they will let you, spend some time throwing coins on the ground, listening to the sounds the detector makes. If the person is REALLY generous maybe they’ll let you borrow it for a few days to make sure this hobby is really one you would like.

Now, you’ve taken the above suggestion and tried out metal detecting, and you think “This is a hobby for me!”… What next?

Well, it’s time for you to buy your own. There are lots of good metal detectors out there. The huge variety is due to different preferences and needs. Generally, there are three “financial” categories of metal detectors.

  • First is the “bargain” or entry level machines. They are the least expensive, and generally offer the least number of options, or somewhat subdued performance. These usually run in the $100 to $300 range.
  • Second is the “mid-level” detector. These are a middle of the road machine, usually offering higher performance or more features than the entry level, but not quite as much as the next category, the high end detector. Here you’re looking at the $350 to $600 dollar range (give or take). For the most part, these detectors have very respectable performance and offer enough to satisfy even the avid hunters.
  • Last, is the “high end” detector. These are the pinnacle of current hobby detectors. They usually offer the best a company has in performance and user options. Now, I know you’re thinking “THAT’S WHAT I WANT!”, please consider that a lot of new users have bought this type right from the beginning and felt frustration when trying to learn so much at one time. Other new users have bought these and been just fine… Here you’re looking at the $700 to $1200 dollar range. That’s a lot of cash!

Ultimately the choice is yours, but my suggestion is either the mid level detector or certain entry level machines for first time hunters. Why? Well, the first thing that causes new detectorists to “fall out” of the hobby is frustration. Frustration of not understanding what the detector is “telling” you, frustration of not finding good stuff every time you dig, frustration from the weight or ergonomics of your detector.

A good entry level machine will let you do what you want….find cool stuff! The definition of “good machine” in this context is one that comes from a reputable company. (Fisher, Bounty Hunter, Garrett, White’s, Minelab, Tesoro, etc.) I, of course, have my “favorite” companies for my own detectors, but I’m not going to suggest them, because I feel that would be unfair to you as a new person to the hobby.

There are many good metal detecting sites where people in this hobby talk about their detectors…here are a few.. this one of course 🙂 www.detectorstuff.com , www.findmall.com, www.thetreasuredepot.com, www.detectorx.com . Most people on these sites are polite and friendly and will be more than willing to offer suggestions and advice to new users. However, be aware, just like some folks like Chevy more than Ford (or vice-versa) there are some who will swear by a certain brand of detector. Take it all with a grain of salt, accumulate all the info. you can, and visit a local detector dealer to check out what they have. DO NOT succumb to strong sales tactics (ie: “Oh, you don’t want that cheap detector! Buy this one *they point at the most expensive one in the store* You’ll like it MUCH better!” 🙂 ) You will also find detector website “sponsors” to be a good moral choice. By “moral” I mean they are the one’s who pay the websites for advertising. As such, the sites are available for reading and information due to their contributions. Without them, little to no info.

Buying used is another option. The sites I listed above will usually have a buy/trade/sell forum where hobbyists swap around detectors. Caution, of course, is advised, and be aware most companies do not allow transferable warranties.

Once you’ve found a good general purpose metal detector, and not paid a fortune for it 🙂 after a while, you may think “Hmmmm, I really like this hobby! I think I’m gonna stick with it!” At this point you’re ready to “consider” buying that “high end” machine you’ve been lusting over 🙂 You should know enough about the hobby by this point to understand what it is you want out of a detector. Who knows? You may find enough with that entry/mid level detector to PAY FOR that top end machine!

Welcome to one of the greatest hobbies in the world!

Garrett Guide to Beach Hunting – On the Beach

garrett_logoAdmit it! Everyone who has ever listened for that buzz of a detector locating its target has dreamed of unearthing great wealth. Even in a sedate, well-kept part where one really can’t expect to find an outlaw cache or pirate treasure, there’s always the possibility of an antique piece of jewelry or a priceless old coin. At the ocean’s edge, the imagined treasures grow even grander. On a more practical note, most hobbyists are just as happy to dig up a single coin and are overjoyed to find more than that. The Typical beach hunter would gladly settle for just the coins and rings lost daily by those who use the water for recreation and commerce.

Thus, if should be a continuing goal of hobbyists to search where targets are most plentiful… to seek treasure where it is hiding, if you will. You can believe me when I say that it has been my experience over decades of treasure hunting that beaches will yield treasure more valuable and in greater quantities than sites away from water.

Think of all the coins, jewelry and other valuable objects that fall into the sand. While you scan a metal detector over the beach or ocean bottom, constantly keep this vision in mind: only a few feet beneath the sand’s surface a veritable “blanket” of treasure awaits the treasure hunter. And, this blanket is continually being replenished!

My advice to any metal detector hobbyist, therefore, is to become a beachcomber. The joys are countless, and the rewards are constantly surprising!

Just what is a beachcomber, anyhow? I describe him or her simply as a person who searches along shorelines. And, what is being sought? Just about anything! There’s always plenty of flotsam, jetsam and other refuse. Often, it’s merely junk, but it can be lost wealth. Out of sight below the sand lies that blanket of treasure awaiting the metal detector. Always remember, however, that the value of any treasure is ultimately determined only by its finder. Keeper finds can be anything from a weathered float to a costly piece of jewelry. Oftentimes, the greatest joy for the beachcomber comes simply from walking the beach, from experiencing soft winds off the water and feeling the sand under bare feet while listening to the tranquilizing sounds of surf and sea breeze. The rewards of a metal detector are but an added bonus.

While beach pickings can be good almost anytime, certain seasons, months and even hours of the day will prove to be better than others. This Guide will point these out. Let me caution you here and now, however, that as a first-time beach hunter, you will probably meet with disappointment. But, don’t most great ventures begin awkwardly and without great reward? Persistence is the key! After just one year, a pleasant “season in the sun and sand”, most reassure hunters will find themselves forever hooked on beachcombing. Too, they’ll be richer for the effort, both in pocketbook and spirit.

Where people congregate, treasure can be found. There can be no disputing that statement; it’s that simple. Try this test. Visit any local park on a pleasant spring or summer day. Count the people and watch their activity. How may did you count? Chances are that you saw a few dozen. What were they doing? They were probably walking, picnicking or perhaps engaged in some sports activity.

Now, drive to a local swimming beach. Make the same observations. How many did you count and what were they doing? You probably counted the same few dozen, plus several hundred more who could lose valuable treasure. And, they too were walking, picnicking or engaged in some sports activity. But, their frolicking and horseplay in the surf or dunes seemed far more likely to dislodge jewelry and other treasures than the sedate activities park.

You can be sure that treasure will be lost at that beach every day. And, I don’t mean “cheap” treasure. People consistently wear expensive jewelry while sunning or swimming. They either forget they have it on, or they don’t understand how they could lose it. It can’t happen to me, they must think. But, it will… and does!

Beach treasures awaiting the metal detector include coins, rings, watches, necklaces, chains, bracelets and anklets, religious medallions and crucifixes, toys, knives, cigarette cases and lighters, sunshades, keys, relics, bottles, fishnet balls, ship’s cargos and other items that will soon fill huge containers. And, for some lucky, persistent and talented hunters, their dream will come true. They will indeed find that chest of treasure hidden by some buccaneer or 17th century Spaniard who never returned to claim his cache.

It’s hard to understand why people wear jewelry to the beach. Yet, they do, and they often forget…even about valuable heirlooms and diamond rings. But, whether sun bathers and swimmers care about losing their possessions or not, it’s just the same for the beachcomber. All rings expand in the heat; everyone’s finders wrinkle and shrivel in the water and suntan oils merely hasten the inevitable losses. Beachgoers play ball, throw frisbees and engage in horseplay. These activities fling rings off of finders and cause clasps on necklaces, bracelets and chains to break. Into the sand drop valuables where they quickly sink out of sight to be lost to all save the metal detector.

How many times have you watched coins, jewelry, keys and other beach “necessities” being placed oh-so-carefully on the edge of a towel or blanket? Then, in a hurry to escape a sudden storm or just through carelessness, the sunbather grabs and shakes the blanket. There go those “necessities” into the sand. Even though the valuables are sometimes immediately recovered, many are never found except by a metal detector.

Boys and girls play in the sand. Holes are dug, and sand is piled up and made into castles and other elaborate structures. In this process toys, coins, digging tools, jewelry, knives and other possessions are lost until the metal detector or keen observer discovers them.

The tale of one such pair of keen eyes on the beautiful beaches of Grand Cayman was related by my good friend Robert Marx. This beachcomber spotted something shining on the sandy bottom in shallow water. To his astonishment it turned out to be a gold cross covered with diamonds. Without telling anyone, he returned later with scuba equipment and really struck it rich. Using only his hand to fan away thin layers of sand, he recovered a fantastic cache of treasure, including a large bar of platinum dated 1521, various bars of silver bullion, a silver bracelet in the form of a serpent covered with emeralds and a large gold ring bearing the arms of the Ponce de Leon family. Since there is no evidence of a shipwreck ever having occurred in the area, the treasure – perhaps the booty of a conquistador – was probably buried ashore and washed out into the shallow sea as the beach eroded.

Few are this lucky –and, believe me, luck is important to the treasure hunter, no matter how great his skill and training-but beach treasures await all of us, ready to sing out in response to the signal of a modern metal detector.

Fill Your Holes

Regardless if you’re new to the hobby, or an old pro, FILL YOUR HOLES! One of the fastest ways to generate some negative PR is to leave unfilled pits in school yards, parks and home yards. I even kick the sand back in when digging at the beach!

Imagine for a moment you know very little about metal detecting. Someone… (friend or otherwise) comes up to you and says “you live in one of the oldest houses in town! can I metal detect your yard?”. You think a moment, then say “well, sure…I guess” (not really sure what that means)… The next weekend that person shows up, grabs this strange looking device out of his pickup truck, and hangs shovels and other digging implements from his belt! You’re thinking “what’s up with the digging stuff?” Next, you see this person swinging this silent weedeater around the yard, then stop, stoop over and start DIGGING! You’re thinking.. “I hope he doesn’t kill the grass!”. In a moment, the fellow stands up, rubs the dirt off his hands and starts doing a jig in the yard. You’re thinking “he must have found something good! Maybe he’ll come show it to me!”… next the fella looks cautiously over each shoulder, then subtly slides the mystery find into his pocket. You’re thinking “well, maybe he’s too busy having fun.. he’ll show it to me before he leaves”. Next the detector guy picks up his stuff, and uses his foot to sort of push the dirt he dug up in the general direction of the huge hole he made. He then stomps on the hole, and starts swinging again. You grab your binoculars, and peering out of the window see that there’s this ugly brown dirty patch where there used to be gorgeous grass! You think, “well, it’s too late now…but I’ll know better NEXT time!….there won’t be a NEXT time!” Needless to say, when the detector dude gets ready to leave, you, the homeowner, asks “Did you find anything good?” Your friend the detectorist says.. “Naw, not much. Just mainly old pieces of junk!” He volunteers to show you what is in his apron, which is pulltabs and rusty nails. However, he neglects to show what got “slid” into his pocket.

Your metal detecting friend drives off into the sunset and you look over your once lush and beautiful yard… it now looks like someone has been lobbing mortars over enemy lines. The holes that did get “filled” are just dirt depressions… You think “never again!”

Here’s an excellent how-to video by SouthCarolinaTeacher.


Now do you see why I say it’s important to fill your holes? 🙂 ….And fill them properly? We’ll have another article soon for proper recovery techniques that don’t “burn your bridges” when it comes to having hunting privileges.

Any other tips or pointers (or gripes 🙂 ) on digging? Post them below in the “comments” box!