Guide to Metal Detecting
This Guide to Metal Detecting has been created to give a basic insight and tips as a hobby for Metal Detecting for the Beginner
The guide will provide the Background on metal detectors, important features and functions of metal detectors, and the basics how to successfully use a metal detector to find Artefacts and coins. This guide will also help you determine which is the best metal detector for you. If you've ever dreamed of searching for buried treasure, or are just looking for a great hobby, it might be time to buy a metal detector. Metal detectors range in price from around £100 to £1000. Metal detecting can provide countless hours of outdoor entertainment and exercise. Best of all you will always find an assortment of coins or other treasure that can actually pay back the original investment! If you have never used a metal detector before you might want to consider joining a local metal detecting club. Many find it a lot easier to learn proper technique from those that have already mastered the hobby. Don’t get me wrong, metal detecting is easy and fun but with a few tricks of the trade you can start out finding the good stuff and prevent wasting a lot of time.
What is metal detecting?
Metal Detecting would probably be defined in a dictionary as something like 'The process of locating metal objects using an electronic device'. However, this rather cold description fails to mention the many aesthetic aspects you will discover when delving deeper into this fascinating hobby.
There are numerous pleasures associated with Metal Detecting, such as healthy outdoor exercise and the companionship of fellow enthusiasts, but there is one exciting component that puts Metal Detecting way above any other pastime - TREASURE!
What is treasure? In short, it is what ever you want it to be, it is anything that is precious to you. If you have it because you love and enjoy it, then it is your treasure. This need for treasure is part of being human and has been an obsession and passion of man since a time before he could even truly be called man. Even from those early beginnings, he has held a desire for treasure, a need to own, love and protect it. Treasure has driven him to travel the world, to fight, even kill, often risking his own life in the name of this desire.
But generally when anyone thinks of treasure, they conjure up images of pirate chests overflowing with gold and silver, of coins, jewellery and other such valuable trinkets. Metal Detecting takes you closer to this perception of treasure than any other pastime simply because valuable items can be, and frequently are, found with metal detectors. However, as you are about to discover, there is much more to this hobby than mere financial gain. Metal Detecting is about the thrill of the chase and the excitement of unearthing an object not touched by man for hundreds, possibly thousands of years. As your collection grows, you will have the satisfaction of knowing that this treasure is yours to hold and look at any time, whilst for most people the view of similar items is hampered by the reflection of museum glass.
Welcome then to a hobby of fascination and mystery, that takes you on a journey through time, unravelling the millions of ways man has used metals to ease and enrich his life. Some of your finds will have monetary value, some will have archaeological value, whilst others may seem mundane. However, they will all have a story to tell, helping piece together the massive jigsaw that is history, and showing us that for thousands of years metal has been used, abused, loved and lost.
Types of Metal Detector
All of the current device type’s function through the use of electromagnetic interference, and most are shaped with a helical loop of some sort at ground level and a counter-balanced neck and handle unit, with a box of electronics for readout or attaching headphones. There are differences in the way they detect metal, what metals they detect best, and the way they communicate with the user.
The rule of thumb is that more expensive metal detectors tend to be more powerful and more versatile. They can detect metal of different sorts, and at a greater depth. In fact, some will even indicate how deep the 'find' is. There are even detectors, too heavy to carry, that look much like flattened lawn care equipment and are wheeled along the ground. The communication is best handled through headphones. These alert you when a contact or hit has occurred.
Generally, from most powerful (and expensive) down, they are:
Very low frequency (VLF)
Very Low Frequency (VLF) detectors are the most versatile and widely used of the popular metal detector types, based on the range of metallic objects you can find with them and the variations of terrain you can cover. As with most detectors, the VLF detector consists of four main parts—an armrest, a control box, an adjustable stem and a round or elliptical search coil. The VLF detector uniquely combines two coils in one. The outer coil acts as a transmitter, using alternating current to create a magnetic field on or beneath the surface of the ground that is easily distorted by a valuable metallic object such as an ancient Roman coin or gold ring—or a worthless item, such as a coke can pull-tab. The detector's inner coil acts as a receiver, reading the secondary magnetic field created by the conductive object, amplifying it and sending it back to the control box. You, the treasure-hunter, hear an identifying tone through the device's speaker and study the response on your LED display. Further steps help you "pinpoint"—to use a common detectorists' term—the object's location. Then, all you have to do is dig. Electronic circuits in VLF metal detectors called phase demodulators help "discriminate" among types of objects. You'll want to "ground-balance" the unit to adjust for naturally occurring minerals in the earth. Adjust the "threshold" to raise or lower the unit's alert level, and use "notching"—pre-set filters—to eliminate an item or range of items from the field of view. But be careful as you attempt to tune out the rubbish. You might miss some valuable items as well.
Pulse induction (PI)
Pulse Induction (PI) metal detectors are popular among gold nugget prospectors, primarily because of their ability to detect objects buried deep underground and filter out the presence of "black sand," or magnetite. Beachcombers also find PI detectors can cut through electromagnetic interference caused by wet salts that typically confuses VLF detectors. Deep-sea treasure-hunters use industrial-sized pulse units, and walk-through airport metal detectors are also based on pulse induction. PI detectors made just for nugget hunters will often feature elliptical search coils that negotiate more easily into tight, rocky spaces. But while PI detectors are more sensitive than VLF detectors, they're less able to discriminate between trash and treasure. Some PI detectors use one search coil as transmitter and receiver. Others employ up to three coils to do the same job. Here's how pulse induction works: The control box sends repeated pulses of electrical current to the search coil, producing a magnetic field. The coil transmits a pulse toward the ground, generating an answering pulse from the target—which, again, could be a precious gold necklace or a vintage pop bottle cap. A sampling circuit measures the pulse and sends it to an integrator circuit, which transmits an audio alert to the treasure-hunter. Time to start digging for gold.
Beat-frequency oscillation (BFO)
Beat-frequency oscillation (BFO) represents the most basic metal detector technology. Budget-minded consumers, beginning hobbyists or parents shopping for a child's first detector may start with BFO, and move on to other types as interest grows. The BFO detector uses two coils—a larger one in the search head and a smaller coil in the control box. Each coil is connected to an oscillator that generates a steady pulse, or frequency. The frequencies vary slightly between the coils, generating radio waves. Tune your detector until you hear an audible beat, or tone. Any metal or mineral in range of the search coil will interfere with the frequency of the radio waves it emits. This, in turn, will cause a change in the duration and tone of the beat frequency. Learn to tune properly and soon you'll be pulling a treasure trove of coins and other artefacts. Metal Detectors can detect objects down to approximately 12 inches below the surface. The exact depth each machine can penetrate actually depends on: the type of metal you're looking for, the size of the target object, the composition of the soil. Dirt which contains high mineral content increases interference and reduces depth penetration, interference from other buried metal and the type and quality of the metal detector. When trying to decide on which machine is right for you start by considering what environment you will be using your metal detector.
Target Alert- metal detectors use one or more of audio, visual, or tactile alerts to let you know when the metal detector has picked up a target signal. Inexpensive metal detectors will have the same beep tone regardless of the metal detected. Other more sophisticated metal detectors will have distinctive beep tones based on the type of metal detected. One example of these is the Fisher 1280x. The Fisher gives a single beep in both directions as the coil is waved back and forth for a good target like a coin. On junk the same machine will beep three times. The most expensive and arguably the best metal detectors will give you a different tone for each type of target. For example The Minelab Excalibur has a low mellow tone for gold and a high pitch tone for coins.
Ground Balance- many metal detectors have settings that allow you to cancel, or adjust for, the minerals in the ground so that the metal detector will not alert you in error. With some machines you can manually adjust the ground balance; the higher-end metal detectors utilize microprocessors to automatically adjust and cancel false signals from ground minerals.
Detection Mode- many metal detectors allow you to change the settings based on the type of object you're looking for. The four most common detection modes are coin, coin/jewellery, relic (buttons, buckles, bullets, etc.) and prospecting (gold). Some metal detectors specialize in just one or two modes, and others let you search in just one mode or in all modes simultaneously. Being able to set a mode for a specific situation helps eliminate false signals
Sensitivity- most metal detectors allow you to adjust the units sensitivity so it is either more or less sensitive to ground minerals, and other objects. This can be very helpful because you can eliminate rubbish and only dig good targets. This feature is however an advanced feature. Beginners should dig all targets because tin foil sounds just like gold. If you eliminate foil you also greatly reduce your odds of finding a gold ring. Most only use this feature in heavy trash areas to cut down the false signals and save time.
Display- the display of any given metal detector is related to its features and functions, more sophisticated metal detectors will display the most information like type of target, target depth etc.
Battery Life- Many metal detectors use 'AA' batteries. Others are rechargeable. Burn times run from only a couple hours to over 30 hours of operation. Consider purchasing an extra rechargeable battery that can be changed in the field. It is the worst feeling in the world to detect all morning and just start to dig jewellery only to have your detectors battery run out.
Size and weight- metal detectors usually weigh just a few pounds, but some are heavier than others. If you are going to be swinging the coil for hours at a time you will want a light weight machine or the ability to mount the box on a waste belt and only swing the coil on an arm.
Budget- After looking through the type of treasure hunting and variety of machine options available sometimes the biggest consideration is your budget.
Once you have a good idea of what specific features and functions you want from your metal detector, you will just need to find the metal detectors that match your needs and begin comparing them by price. Try to find the metal detector that provides the most value. If budget is a major concern, consider purchasing a used metal detector.
Coil-swinging: How do I use my detector?
The best way to consistently find artefacts with your metal detector is to practice hitting your targets. Learn how to move your search coil and to identify types and depth of hidden metal objects by listening to your detector's signal tone. If it beeps, dig it.
Adjust the search coil of your detector so that it's ½" above the ground and even with the surface. VLF detectors (link to VLF section under first anchor link on title page) are motion-based, so keep the coil moving while you search. Swing from the shoulder, keeping your arm relaxed. Complete an arc of three to five feet, holding the coil level at the end of your swing to avoid false signals. If you're swinging your detector in a pendulum motion, you're swinging it wrong. Methodical searches yield better results. Pick a section of ground and stay in that section. When you've worked one area, move on. If you encounter a weak signal, try moving the coil in short, rapid sweeps over the target zone. Most diggable objects will respond with a repeatable tone. If the signal does not repeat after you sweep the coil directly over the potential target a few times, it's most likely trash metal. Practice with the discrimination settings. You can tune out pull-tabs, but then you'll probably miss nickels and aluminium and iron objects.
When you find a target, you'll want to "pinpoint" it. Pinpointing lets you narrow your search pattern and dig as small a hole as possible when extracting your treasure. In pinpoint mode, your detector penetrates more deeply, but is unable to classify targets. When you're ready to pinpoint, start by setting the "ground balance," to offset the effects of soil mineralization. To pinpoint, sweep the coil over the target in a narrowing side-to-side pattern. Take visual note of the place on the ground where the "beep" sounds. Then, move forward and back over the target, and again note where you hear the beep. If necessary, "X" the target from different angles, shortening your swings to locate the target. When you think you've found it, dig a hole. A bottle cap or ball of foil might be all that emerges, but at least you'll know people have visited that site. You're bound to find something interesting if you keep looking.
Buying a metal detector
Unfortunately, there is no detector that will perform perfectly on all terrain. Should you want a detector for one purpose only, then choosing a detector is a relatively simple task. Most of us, however, want a detector for a variety of different terrain and so will need to choose carefully to get as close as possible to our requirements. A browse through any magazine such as the Treasure Hunting and Searcher magazine is all that is needed to demonstrate that, as a potential metal detector buyer you are spoilt for choice. There so many to choose from that even for the seasoned detector enthusiast the task is made no easier. So where do you start? How do you sift through the metal detector minefield and find the detector best suited to your needs? This short guide has been prepared to take you through this process:
The first consideration is to decide how much you are prepared to spend and if that amount is to include accessories (the most important of these being headphones and a digging tool).
The next question is where will most of your detecting be carried out? This is possibly the hardest question to consider, especially for the beginner, but it does have a bearing on what you buy. The easiest approach if you are not sure is to think about your geographical location, as most people tend to detect locally. For instance, are you near enough to the beach and know you will detect there? Perhaps you live inland and will never visit the beach, but will your sites be on arable land, pasture or park land, etc?
The weight of your new detector is also important as it is no good ordering the perfect detector only to discover you can hardly lift it!
Finally do you want new or used? A new detector will offer you piece of mind in having a full manufacturer's warranty (and in some cases free accessory packs), but choosing second hand will enable you to buy higher up the range. Once you have these basic questions answered, it is time to read the brochures and look at the detectors that fit into your classifications. Finally, don’t be afraid to ask the questions the brochures never seem to answer. Remember, your new detector is going to be your companion for a long time and your success in the hobby depends on you making the right start with the right equipment.
Metal Detector Accessories
When you get your first metal detector all of a sudden you realize you need other metal detecting accessories.
You need a digger of some sort, ground cloth and a pouch to put the rubbish and treasures that you find in. You don't need to buy all of this stuff now, but something to think about.
You need some sort of digging tool to dig with. You can start out with just a basic garden trowel, and then graduate to a small spade of digger.
If you plan on digging the soil, then a ground cloth can be a very helpful item in recovering your target. Where do you get a ground cloth? Make one. You can use a pair of old jeans cut them above the thigh and above the knee, and then cut it along the seam.
The jean material has proven to be very durable too, as you can see. You can staple on two pieces of wood to the cloth to make dumping the soil easier, but make sure the staples are small enough that your detector doesn't detect them.
Or alternatively you can use a plastic carry bag to do the job.
Here's how you use it.
When you cut a flap in the grass, and start scooping out soil, place it on your ground cloth that is laying close by. Then scan the soil to see if you got the target, or if it's still in the hole. Once you locate the target, pick up your ground cloth carefully from the sides with the soil still on it, and pour the soil back into the hole, press the grass flap back down, and step on it to secure it. How simple!
And you don't leave any telltale signs of you having been there either, no dirty grass! Once you start using one, it's hard to go without one. If you don't use one, your target will likely fall out of your soil, and then you will have to locate it again in the surrounding grass or leaves.
It is all ways handy to have a Finds Pouch as you detect, this allows you to place all your finds that you have made into it and also allows you to carry other implements i.e. probe, cleaning equipment etc
Metal Detecting Headphones
Headphones are a must! Sometimes when you buy a metal detector the dealer will throw a pair of headphones in with it, but sometimes not. If you ask, they just may do it. Make sure they have volume control, preferably waterproof and stereo would be nice.
Batteries and Battery Charger
Also, last but not least, keep a good supply of batteries with you. You can start out using regular AA's and then invested in some Nickel Metal Hydride batteries and a battery charger. These could last you a couple of years. There's nothing worse than getting all the way out to the field and having your batteries die.
How deep can a good detector be expected to find coins?
This question is much easier to answer nowadays because virtually all modern detectors are 'motion' or VLF discriminator types. Most of them are also fitted, as standard, with search coils of around 8" diameter, which is generally regarded as the optimum size for coin hunting on sites with moderate amounts of metallic litter. Using an incorrect sweep-speed will also affect depth, but the following figures are achievable with a correctly used detector:
5p-10p sized targets - 4 to 8 inches
2p-50p sized targets - 6 to 12 inches
Fruit jar lid sized targets - 8 to 16 inches.
Many other factors can affect your detector's depth, but the same factors will affect all other detector depths. The two most important things for you to do today are to become familiar with your machine, and to use it at the proper sweep-speed.
Can one detector 'do it all'?
Some of the better 'all purpose' detectors can make a pretty good job of most treasure hunting assignments, but there are certain machines specifically designed for such tasks as underwater work and gold nugget hunting. These specialised types are less adaptable to general purpose work.
Are detectors with lots of knobs better than those with just a few knobs?
All detectors fall into one of two classifications; 'turn on and go' or 'do it yourself'. The first group have either a preset ground adjust, or an automatic ground adjust. They do not require any further adjustment by the operator because the electronic circuitry takes care of eliminating mineral effects. The 'do it yourself' group usually have a multi-turn ground adjust knob which must be set to the correct position by the operator. Such machines are generally capable of just a little more depth provided they are set correctly, but they yield much poorer results when incorrectly adjusted. Both 'turn on and go' and 'do it yourself' units can be very effective.
What kind of detector should be used for [a] relic hunting and [b] coin hunting?
An all purpose detector will do both jobs, although a larger coil might be an asset whilst relic hunting. For coin hunting, a motion discrimination detector is virtually essential if you wish to avoid digging out every bit of iron you find in the ground. Other features, such as notch discrimination, target identification and coin depth indication can be regarded as optional extras.
What's the difference between concentric and wide scan coils?
A concentric coil is better than a wide scan at discriminating, but it is much more affected by the ground you are hunting. A wide scan coil is less affected by the ground and it can be a superior coil in areas of high mineral concentrations and on salt water beaches.
Which coil size is best?
For an all purpose detector, the standard coil supplied with the unit is usually the optimum size for most hunting. In extremely littered areas, a smaller coil (4" or 7") will usually bring better results; even though the smaller coil has less depth on coin-sized targets, your results will be better because good targets are less likely to be masked out by bad targets lying next to, or over them. When searching in relatively clean and litter free areas, a larger coil (10.5" or 11") will usually yield better depths and a wider area of coverage because masking of good targets is less likely to be a problem.
How much discrimination should I use?
If you are serious about finding gold rings and gold coins, use as little discrimination as possible. Most gold items are rejected at about the pull-tab level of discrimination, so by eliminating pull-tabs, you are also eliminating all the gold targets. Even if you use a notch discriminator to reject pull-tabs, you will lose all those gold targets which have the same phase response (or 'electronic fingerprint') as the pull-tabs.
A truly serious hunter, and one who has been successful over many years, will have dug many pull-tabs, but that is why he has also found most of his gold targets. With today's motion machines, it is pretty easy to get rid of most of the iron objects, but those iron objects could be masking good targets beneath them.
What is the purpose of notch discrimination?
Notch discrimination can be used either to reject a narrow band of targets (=notch reject), or to respond to a narrow band of targets (= notch accept). It is usually used to reject pull-tabs while still finding 5p and 10p coins and those gold rings which do not have the same response as pull-tabs. The notch level control generates a 'window signal' whose width is set by a small component on the PC board. This 'notch window' can be moved up and down the discrimination range until it properly covers the desired range of target response.
If the detector is being used to eliminate the response to the pull-tabs, you must remember that any good targets which have the same phase response as pull-tabs, and which therefore fall within the same window, will also be eliminated. Such good targets consist mainly of gold items and rings. The 'notch accept' feature can be used to tune the detector to a particular type of item, such as a known type of ring. The detector will then only find items which fall within that narrow notch window.
Does using notch discrimination cause loss of depth?
Yes it can cause a small loss of depth, for two reasons. Firstly, the notch discriminator adds a slight amount of capacitance to the normal discriminating circuit, and this slows the detector's response to targets. Sweep-speed then becomes more critical when seeking deep targets, but if the detector is used at the correct sweep-speed, the loss of depth will not amount to much. Secondly, Signal strength diminishes at the top and bottom edges of the notch window. As the target approaches the response cut-off of the filters used, its signal weakens. Setting the top and bottom edges of the notch window will cause some loss of depth on those targets. However, a properly adjusted notch window will not cause a great deal of depth loss.
How do I adjust the sensitivity control to get maximum depth?
First find out which modes are affected by the sensitivity control on your detector. Do it by turning your machine according to the instruction manual, and then waving a good target over the coil with the sensitivity control set first at the maximum, then at the minimum position. If the detecting distance alters, then the sensitivity control is functioning. When using the detector on site, set the sensitivity control as high as ground conditions will allow you to use the machine without too many false signals or spluttering noises. Too many spurious signals will make hearing the weak responses of good, but deep targets difficult.
How does target ID work?
If you have any kind of discriminating metal detector, you already own a 'do it yourself' ID machine. By increasing the discriminate level until the target just disappears, you can tell what the target is. All of this is done automatically and very rapidly by a target ID detector as you swing the coil over each target. Basically, the electronics measure the phase angle of the target at the moment the signal occurs. It generally takes only one pass over the target to get accurate identification, although the earliest models required several swings, which is why they were know as 'pump up' ID detectors. However, on older sites, many ancient coins and artefacts may show as junk or reject signals. ID detectors therefore are best suited to searching for modern coins.
Is manual ground adjust better than fixed ground adjust?
A fixed or automatic (i.e. factory preset) detector will always give good performance, no matter what type of ground you are hunting on. A manually adjusted machine may increase the detection depth by a small amount, but only if the adjustment is very accurately carried out. Incorrect adjustments may give horrendous results. For the average user, a preset or automatic detector's performance is superior to the results that might be obtained with an improperly adjusted manual machine.
Are battery test readings accurate?
Only if the tests are done while the batteries are delivering the proper amount of current to the detector. Some cheap battery testers, and even some more expensive meters, may give erroneous results when used to test batteries that are not delivering current during the test. An audio test is much more reliable since the audio circuitry loads the battery to the detector's full power while the test takes place.
By how much will the use of headphones increase battery life?
Since the speakers in most detectors are of 8 or 16 ohms impedance, while most detectors use a resistor of approximately 100 to 200 ohms to limit the sound output in the headphones, the current necessary to drive a set of headphones is considerably smaller than that required to drive the low impedance speaker. Using the figures just given, a set of headphones would increase battery life by 2 or 3 times. However, since the electronic circuitry in the detector is always operating when the machine is switched on, even though the detector may not be making any noises, the savings on battery life may not be as big as the above numbers seem to indicate.
Why does my detector sometimes detect rocks and tree roots?
The detection of rocks can be due either to your detector's ground adjust not being set correctly so that typical 'hot rocks' are ignored, or to the rock that you have just found being a truly positive reading mineral sample. Hot rocks are iron ores or magnetites, which are 'negative' with respect to normal ground signals. Their intensities can vary considerably, which makes setting the detector to get rid of all of them a little tricky. Early motion detectors usually 'beeped' at hot rocks, but switching to all metal yielded a 'null' response. Since the hot rock was negative in all metal and also negative in discriminate, both signals were the same, and the detector said 'good target' even though it was really bad. Today, most manufacturers set the ground adjust so that the filtered all metal signal responds in a positive fashion to hot rocks. Therefore, the signals are different, so the detector doesn't beep at negative hot rocks. However, minerals come in many different forms, and some of them are detectable. Tree roots can also absorb various chemicals and end up being electrically conductive. Sometimes, all you can do is grin and bear it.
Will meter detectors find coins deeper than non-meter detectors?
Not generally. It takes some kind of circuitry to drive the meter, and if that circuitry has more gain than that which drives the speaker, it may be possible to detect deeper with the meter. But virtually all manufacturers realise that if they can get deeper performance, they will add the extra gain to the audio stage as well.
How do I overcome interference from other detectors when I am at a rally?
Interference occurs when two detectors of similar frequencies operate in close proximity. The nearer the frequencies, the further apart the two detectors will interact. Crystal controlled detectors are especially prone to this problem because the crystals are very accurate. The only solution in that case is to fit a 'frequency shifter box' or to get further away from the interfering machine.
Are 'audio enchanters' any good?
They operate by amplifying weak signals and attenuating strong signals. Thus, they tend to make all signals sound alike. They can be helpful when you are hunting in TR discriminate, or in all metal mode, or if your detector has an 'audio threshold'. However, on 'silent search' detectors are less effective, though they do limit the sound in your headphones when you pass over a piece of surface junk. This can add to your comfort during extended search periods.
What is ground cancelling, and how can I adjust my detector to the right point?
Think of ground cancelling as being exactly the same thing as discrimination. If your ground control is set too low (counter-clockwise) the detector with 'reject' the ground. If your ground control is set too high (clockwise) the detector will 'find' the ground by beeping as the coil approaches the ground. Your aim is to set the ground control so that the detector remains neutral to the ground, or doesn't see the ground at all. It will then detect as deep in the ground as it does in the air. To accomplish this, first tune the detector to a threshold tone while holding the coil in the air. Then lower the coil to the ground and listen. If the threshold dies away, turn the ground control in a clockwise direction. If the threshold tone gets very loud, turn the ground control counter-clockwise. Next, raise the coil, retune to a threshold tone and repeat the above operations. When you get it right, the sound will change very little as you lower the coil.
Why does my detector find large deep nails and rusty iron even when set to reject pull-tabs?
Unfortunately, most motion detectors can be fooled by large rusty items, especially if those items are circular, such as iron washers and steel bottle caps. Sweeping the detector faster will help a lot on the steel bottle caps, and it will help some on the washers. Fortunately, large pieces of iron will be heard as much 'broader sounding' targets than non ferrous items in the all metal mode. Experienced motion detector users rarely dig large pieces of iron.
Does the moistness of the soil affect detection depths?
A lot of metallic targets corrode when lying in damp soil. This can cause the target to appear much larger than it really is. When the soil dries out, the corrosion may not affect the detector and the target will seem more like its normal size. Gold doesn't corrode in the ground, and silver doesn't corrode nearly as much as copper, brass and bronze. Iron and steel, of course, rust in moist ground, and can cause some really horrendous false signals.
Is depth sacrificed for accurate identification in a target ID detector?
Virtually all target ID detectors can find targets much deeper than they can identify them. Discrimination only requires one reference signal, which yields a positive signal for good targets and a negative one for bad targets. To identify the target requires some very special and complex electronic circuitry which does not have the ability to reach the same depth as a simple discriminator. If manufacturers limited the depth of their ID machines to the depth of the identifier circuit, they would sell a lot fewer detectors.
How should I adjust the discriminate level on my detector to achieve maximum depth?
For maximum depth, set the discrimination level as low as possible. To get the absolutely best depth, set the discrimination level at the point where you get a broken signal, rather than no signal at all, from the type of object you want to reject. This will give you some additional signal on all good targets that are heard.
By how much, and in what ways, is a £500 detector better than a £300 detector?
The £300 detector will probably have the same depth as the £500 machine, but it will not have all the features of the more expensive unit, such as a meter, depth measuring ability, notch capability, target ID, multiple discriminate levels, surface blanking, and the other 'bells and whistles' that can raise the cost of a basic machine. But unless you really want those features, and understand that you will consume a lot more batteries by powering them, why pay for them? Although some manufacturers may put less gain in their cheaper models, you should expect to find only fewer features on your £300 detector.
What is the best operating frequency for finding gold?
Typically, most VLF detectors, made today operate in the 5 to 15 kHz range, while gold detectors typically operate at about 20 kHz. The increase in frequency gives a minutely greater response to tiny bits of gold, but the increased response to small targets results from them having about ten times as much gain as general purpose detectors. Increasing the frequency much above 20 kHz gives a tiny bit more response in air tests, but the increase is lost as soon as the target is laid on the ground.
Permission to Search
Every single piece of land in this country has an owner, and if you want to metal detect on that land then you need the owners permission. It is always best to get the landowners permission in writing if you can. You can always combine a permission to search agreement with a finds division agreement - kill two birds with one stone.
If you are successful in getting permission to search, remember to ask the landowner if there are scheduled monuments on his or her property - this is particularly important - as you cannot detect on a scheduled monument even if you have the landowners permission. To search a scheduled monument requires a license that you are very unlikely to get.
Finds Division Agreements
Be sure to agree terms with the landowner on finds division before you even think about detecting on their land, and get this agreement in writing. A finds division agreement could save you from a legal nightmare should you find a valuable item or hoard.
The vast majority of farmers and landowners are honest hardworking people, who would never dream of trying to rip you off, but the sight of gold and silver can do strange things to people - it is better to have a finds division agreement and not need it than to need a finds division agreement and not have it.
Getting Permission Letter
This a sample letter that you may wish to use to gain that permission to detect on some ones land
This may sound like a strange request, so let me introduce myself: My name is (Your Name) and I have lived in (Name of Town) for (Length of Time). I am (Your Age) years old, married with four children. Normally I would prefer to approach you in person, however I feel that a letter before hand is a better emissary than just knocking on your door at an inconvenient time and invading your privacy.
I have been engaged in the hobby of metal detecting for twenty years and find it a healthful, enjoyable pastime that allows me to meet many interesting people. The thrill of finding old coins, buttons, etc. is very exciting to me.
Recently, I have researched information that your property and the area surrounding it goes back many years. I would like to obtain permission for myself to detect your property.
I want you to understand that I always respect the property that I search and try to leave it in the same condition that I found it. Normally the targets are no deeper than 4 or 5 inches and I retrieve them such that the ground appears not to be disturbed.
In addition, I would like to offer my services to you. Perhaps you or someone you know has lost a valuable ring, a cache or a farm tool. I would be willing to assist just for the thrill of the search.
I have enclosed a self addressed envelope for your convenience and would be happy to meet with you if further discussion is required.
Thank you for your time and consideration.
National Council for Metal
What is the National Council for Metal Detecting?
The National Council for Metal Detecting is a representative body of elected volunteers formed in 1981 to provide a means whereby responsible metal detector users would have a democratic forum to discuss problems affecting the hobby and to provide an
authoritative voice to counter ill -informed and frequently misleading criticism of the hobby. It does not represent the trade or archaeological interests. The NCMD has gained Government recognition as an organisation which represents metal detector users countrywide. It has played a major role in representing the views of those metal detector users to Government Departments regarding legislation affecting the hobby. The National Council for Metal Detecting has a written Constitution which is available to all members. It is a member of the Central Council for Physical Recreation.
The National Council for Metal Detecting Code of Conduct
1. Do not trespass. Obtain permission before venturing on to any land.
2. Respect the Country Code. Do not leave gates open, and do not damage crops or frighten animals.
3. Wherever the site, do not leave a mess or an unsafe surface for those who may follow. It is perfectly simple to extract a coin or other small object buried a few inches below the ground without digging a great hole. Use a suitable digging implement to cut a neat flap
(do not remove the plug of earth entirely from the ground), extract the object, reinstate the grass, sand or soil carefully, and even you will have difficulty in locating the find spot again.
4. If you discover any live ammunition or any lethal object such as an unexploded bomb or mine, do not disturb it. Mark the site carefully and report the find to the local police and landowner.
5. Help keep Britain tidy. Safely dispose of refuse you come across.
6. Report all unusual historical finds to the landowner, and acquaint yourself with current NCMD policy relating to the Voluntary Reporting of Portable Antiquities.
7. Remember it is illegal for anyone to use a metal detector on a protected area (e.g. scheduled archaeological site, SSSI, or Ministry of Defence property) without permission from the appropriate authority.
8. Acquaint yourself with the definitions of Treasure contained in the Treasure Act 1996 and it’s associated Code of Practice, making sure you understand your responsibilities.
9. Remember that when you are out with your metal detector you are an ambassador for our hobby. Do nothing that might give it a bad name.
10. Never miss an opportunity to explain your hobby to anyone who asks about it.
The Portable Antiquities Scheme
The Portable Antiquities Scheme is a voluntary scheme to record archaeological objects found by members of the public in England and Wales. Every year many thousands of objects are discovered, many of these by metal-detector users, but also by people whilst out walking, gardening or going about their daily work. Such discoveries offer an important source for understanding our past.
This website provides background information on the Portable Antiquities Scheme, new articles, events listings, and access to our database of objects and images.
The Treasure Act
All finders of gold and silver objects, and groups of coins from the same find spot, which are over 300 years old, have a legal obligation to report such items under the Treasure Act 1996. Now prehistoric base-metal assemblages found after 1st January 2003 also qualify as Treasure. This website provides further information for finders of potential Treasure.
Summary of the Treasure Act
What is the definition of Treasure?
The following finds are Treasure under the Act, if found after 24 September 1997 (or, in the case of category 2, if found after 1 January 2003):
Any metallic object, other than a coin, provided that at least 10 per cent by weight of metal is precious metal (that is, gold or silver) and that it is at least 300 years old when found. If the object is of prehistoric date it will be Treasure provided any part of it is precious metal.
Any group of two or more metallic objects of any composition of prehistoric date that come from the same find (see below)
All coins from the same find provided they are at least 300 years old when found (but if the coins contain less than 10 per cent of gold or silver there must be at least ten of them). Only the following groups of coins will normally be regarded as coming from the same find. Hoards that have been deliberately hidden smaller groups of coins, such as the contents of purses, that may been dropped or lost votive or ritual deposits. Any object, whatever it is made of, that is found in the same place as, or had previously been together with, another object that is Treasure.
Any object that would previously have been treasure trove, but does not fall within the specific categories given above. Only objects that are less than 300 years old, that are made substantially of gold or silver, that have been deliberately hidden with the intention of recovery and whose owners or heirs are unknown will come into this category.
Note: An object or coin is part of the ‘same find’ as another object or coin if it is found in the same place as, or had previously been together with, the other object. Finds may have become scattered since they were originally deposited in the ground.
What should I do if I find something that may be Treasure?
You must report all finds of Treasure to a coroner for the district in which they are found either within 14 days after the day on which you made the discovery or within 14 days after the day on which you realised the find might be treasure.
Take Advice Before Cleaning
Show your finds to your nearest FLO, who will help identify them and advise you on good practice. Once you are certain the find is not Treasure you can decide what to do next. A professional conservator might not charge as much as you think. You can find an accredited private conservator through the Conservation Register or through your local museum. Some of your finds will be collectibles, such as livery buttons, pilgrim badges, hammered coins and tokens; others may be agricultural in origin, like horseshoes and harness fittings. As a rule of thumb, the older the item, the more heavily corroded it will be, and many ancient objects made from copper alloy will have developed a patina which adds value and beauty to the object. Removing this patina could seriously damage and devalue the object and lose information. But many of your finds will be fairly modern, like milled coinage, watch-fobs, penknives and other casual losses. These more recent items can mostly be cleaned carefully without them coming to harm but there are no quick fixes'!
Cleaning by hand is the best way to remove thick corrosion layers, working with fine hand-tools and with the aid of a low-power microscope. Use sharpened wooden or plastic points such as cocktail sticks and artist's brushes to remove loosened soil. Practice first with scrap objects until you get experienced at it, as much skill and practice is needed to produce good results. Don't use barreling, wire brushes or other harsh methods they will only cause damage. Remember, the purpose of cleaning an object is to reveal the original surface detail. This surface may be within the layers of corrosion and no longer be metallic.
Many metal corrosion products are poisonous, so wear a dust-mask and disposable gloves, especially when cleaning lead alloys. Chemical cleaning should only be used to remove tarnish from more modern objects where the original surface is well-preserved.
Always remember that chemicals can be dangerous to you and your finds and great care should be taken in their storage and use at home. Chemical reactions cannot easily be controlled and some chemicals may remain in the object and cause problems later. Even lemon juice and vinegar are chemicals and can cause damage to metal surfaces. Use only materials designed for the job.
If you must remove tarnish from silver, polish brass items, and remove the rust from your ironwork, then there are lots of proprietary products available at hardware stores. But be warned: none of these products are conservation-grade materials, and you use them at your own risk. When undertaking chemical cleaning:
Watch out for additional materials, such as inlays or plating, they can be fragile.
Watch out for attached organic remains': Don't let the chemical product come into contact with bone, leather, wood, textiles etc.
Wash off any chemical cleaning agent from your object very thoroughly after use.
Joining: For objects in fragments that need joining, it is important to find the right adhesive for the particular material. Adhesives used with artifacts should ideally be reversible, so you can easily undo the join using a solvent if you make a mistake. For corroded metals, use a recommended reversible adhesive, such as Paraloid B72' or cellulose nitrate' from a specialist supplier. Never use super-glues as they can be chemically unstable, and are difficult to apply and control. If a stronger joint is required for a large or heavy object, you may have to resort to an epoxy adhesive, such as Araldite ® . If you do use an epoxy, make sure it is of good quality and the right sort for joining metals. But remember: you may never be able to undo it again!
Never solder or weld objects; any process involving heat will change the metal's structure and obscure detail.
Coatings are commonly used both to protect and enhance the surfaces of objects. But a surface coating is seldom really necessary for protection if you are handling your finds correctly and storing them in a dry box'. If you must apply a coating to your finds:
Don't use domestic waxes, oils, petroleum jelly or shoe-polish they all contain potentially harmful contaminants
For bright metal surfaces, use an appropriate lacquer, such as Incralac'
For corroded metals, coatings can be used to consolidate a fragile surface. Use a conservation-grade resin solution, such as Paraloid B72'
Make sure you read instructions carefully, especially health and safety advice, before using any specialist materials.
Restoring: This is the process of filling holes and gaps or making up spare parts for an object which are missing. If carried out in such a way that the restoration is invisible, it amounts to faking, which is both misleading and dishonest. If an object is damaged, then this is part of its history. It is better to leave it alone and let it tell its story without intervention!
A test performed by passing metal samples of various sizes under the detector's search coil to check target responses. This test is not an accurate indicator of ground depth penetration.
A type of battery characterised by the ability to sustain longer periods of current drain and greater storage life than standard carbon-zinc batteries.
Describes any mode or control setting that allows total acceptance of metal targets. Usually associated with ground balance mode.
Circuitry producing different audio tone for each target's conductivity range, e.g. low tone for iron, high tone for coins.
Circuitry which continuously retunes the detector's threshold to the initially tuned audio level at a preset rate after drift and/or target rejection.
A false signal caused by a rejected target coming within one inch of, or contacting, the bottom of the search coil when operating in the discriminate mode.
An air test to determine at what approximate discriminate settings various metal samples are rejected or accepted. The test is conducted in non-metallic area.
One of the most extreme components of non-conductive, negative ground minerals. Also called magnetite and magnetic iron oxide.
A method of fastening the detector's control box to expand usability for shallow water hunting. Also known as hip mount.
Standard dry cell batteries.
Coin Depth Indicator:
A visual indicator, used in conjunction with calibrated circuitry, to show depths, in inches or centimetres, of buried coins.
A search coil configuration using one or more transmit, and one receive, winding having unequal diameters aligned on a common centre, most recently arranged on the same plane and called 'coplaner concentric'.
Wet salt sand which produces a positive rise, or metallic response on an air tuned threshold.
The measure of a metal target's ability to allow eddy currents to generate on its surface.
The densest or strongest region of the search coils electromagnetic field where detection occurs. It is balloon shaped and changes in size directly in proportion to target surface area.
Adjusting the audio threshold into the null or less sensitive tuning zone. It is also a method of narrowing a target's signal width manually for precise pinpointing. This is accomplished by returning to audio threshold over the target response area.
Adjustable circuitry which ignores or nulls audio responses from a specific conductivity range allowing positive responses to be heard from metals higher in conductivity above the discriminate control setting. Designed primarily to eliminate audio response from unwanted metals.
A loss of threshold tuning stability caused by temperature change, battery condition, mineral content, and/or detector design.
Small circulating currents produced on the surface of metal by the transmitted electromagnetic field. These currents then produce a secondary electromagnetic field which is then detected by the search coil receiver windings, resulting in inductive imbalance between the windings.
An invisible force extending from top to bottom of the search coil and created by the flow of alternating oscillator frequency current around the transmit winding.
A metal foil wrapping of the search coil windings for the purpose of eliminating electrostatic interference caused by wet vegetation.
Descriptive of any iron bearing material.
An oxidised particle of iron which becomes non-conductive and makes up the natural negative ground mineral matrix. Hematite, which is also an iron oxide, will respond as positive or metallic.
The number of complete alternating current cycles per second produced by the transmit oscillator. Measured in Hertz (Hz). VLF = Very Low Frequency; LF = Low Frequency; MF = Medium Frequency; HF = High Frequency.
A state of operation in which specialised circuitry can be adjusted to ignore the masking effect that iron ground minerals have over metal targets.
A feature requiring a manual control adjustment procedure to neutralise the effects of negative minerals in the search matrix.
A feature which eliminates the manual ground balance control and its adjustment from the operators set up procedure. This adjustment is performed internally by the factory to optimise operation over an average range of non-conductive soils.
Complex circuitry found in motion type detectors which separates mineral signals from metal signals, allowing the metal signal to be further processed by the discrimination circuitry.
A rock which contains a higher concentration of non-conductive ground minerals than the surrounding matrix to which the detector is balanced. A metallic (positive) response will be heard in the motion and non motion modes, and a null or negative drop in threshold is heard in the all metal ground balance mode over these rocks.
LCD (Liquid Crystal Display):
Used on a metal detector as a graphic visual indicator.
LED (Light Emitting Diode):
A semiconductor which produces an illuminated visual response.
Refers to the total volume of ground penetrated by the transmitted electromagnetic field which may contain varying amounts and combinations of minerals, metals, salts and moisture.
Metallic substances: iron, foil, nickel, aluminium, gold, brass, bronze, lead, copper, silver, etc.
A person operating a metal detector in the field. This name is preferred by many to 'treasure hunter'.
Mineral Free Discriminator:
Detector that can reject or ignore trash metals while simultaneously eliminating or balancing ground mineralisation.
Any soil that contains conductive or non conductive components.
Soil that contains non-conductive minerals which have a negative or nulling effect on air-tuned threshold.
Soil lacking non-conductive or conductive mineral properties. It lacks mineralisation.
NiCad (Nickel Cadmium):
A rechargeable battery.
Not of iron; metals including gold, silver, copper, lead, tin, brass, bronze, etc.
Mode of operation that does not require search coil movement to trigger target response.
Operation whereby all target responses are 'tuned out' except those the instrument is adjusted to accept in the notch window.
Circuitry which allows a desirable window of targets to be accepted within the rejection range of unaccepted targets.
A control used to select the target level of conductivity which the notch filter will act upon.
Operation whereby all targets within the notch width (at the chosen notch level) will be 'tuned out'.
Zone just below audible threshold in detector tuning. The term also refers to the momentary drop, or quiet response, of threshold audio as the search coil passes over a discriminated or rejected target.
The amount of search coil swing advance not greater than the search coil's physical diameter.
Finding the exact target location with respect to a search coil's designated centre. Accomplished by interpreting the centres of audio response width in perpendicular directions or scans.
PI (Pulse Induction):
A metal detector with a transmitter circuit that pulses an electric current into the ground before quickly shutting down. The eddy currents dissipate immediately from wet salt sand and other ground minerals because they are poor conductors. Because they are better conductors, metals hold the eddy currents, and when the receiver circuit comes on, it picks up the returning signals from metal objects.
Radio frequency detector with 2 separate coils, the detector is capable of detecting large, deep objects while naturally ignoring small targets such as nails and individual coins.
The effective search coil detection width. Also refers to search coil movement over the ground.
Search technique in which the search coil is pressed and held in contact with the ground in order to maintain an even audio threshold. With newer detectors, this technique is used to gain depth.
A circular (or other shaped) plastic housing containing single or multiple transmit and receive wingdings in a specific orientation or configuration to emit and receive signals from ground and targets. (Also called a 'loop' or a 'coil'.)
Search Coil Cable:
An electrostatically shielded cable of conductors (wires) which convey signals to/from the search coil and control housing.
The measure of capacity of a detector to perceive changes in conductivity within the detection pattern. Generally, the more sensitivity a detector can smoothly provide the more depth it will achieve.
(= silent operation) A detector capable of producing a target signal while operating below the threshold audio.
(=coil cover or scuff cover) A protective cover for the search coil bottom.
A description of search coil speed required to operate the motion discriminate mode.
The motion employed in moving the search coil across the ground.
Occurs when large pieces, or high concentrations, of trash metals drive the threshold into the null zone, suppressing weaker responses from deeper or smaller targets.
A control which can be manually rotated ten times to cover the full electrical range of the function. Usually associated with tuning or ground balance