Difference between mono and dd coils. Homemade coil for a pulse metal detector. According to the shape of the coils

Below we will talk about coils for metal detectors. What are they, why do we need small ones, why do we need large ones?
In addition, we will touch upon the scope of applicability of coils.

DD and Mono Coil Metal Detectors

The mono coil of a metal detector consists of 2 concentric circles - one smaller, the other larger. Look at the photo:

The signal under this coil propagates in the form of a cone. (We will show a picture of this signal later)

The DD coil (or DoubleD) resembles two inverted English letters D. That is why it is called that. And in appearance it is a circle or an ellipse with a longitudinal spoke. Look at the photo:


The signal from such a coil travels along the longitudinal spoke and has a wider shape than that of a Mono coil.
Compare the two coil signals:

Of course, this figure shows the difference schematically. The signal from the DD coil goes wider. But a Mono coil usually hits deeper.
DD metal detector coils are recommended for use in highly mineralized fields.
Recently, all manufacturers prefer to install DoubleD coils on their metal detectors.
It should be noted that DD coils are more expensive to manufacture than Mono. This affects their price.

Look at another picture. In our opinion, the difference between a DD and a Mono coil is shown here more correctly.

The green area is the coverage area of ​​the DD coil. It can be seen that in one direction she loses to Mono, in the other she wins. True, not as big as in the first picture. IN reality not very big. But at a depth where the Mono coil can barely reach, the coverage with DD is wider.

Why are different coil sizes needed?

As a rule, the manufacturer installs a standard 9"-10" search coil on its metal detectors.
This is considered medium size. With this reel you can walk across most fields.
But if there is a lot of metal debris, then you have to install a coil of smaller diameter. Usually - 6".
This is required because several targets fall under the large coil at the same time: colored nails and black nails. In this case, the metal detector gives a black signal. Or incomprehensible at best.
Reducing the coil diameter avoids this situation.

If we have a small density of debris, then we can increase the search depth by taking a coil of a larger diameter. In addition, we will reduce the number of missed targets when searching. (see picture above)

Coil shape

Coils for metal detectors are either round or elliptical. Elliptical coils are more difficult to manufacture. But they provide some advantages when searching.
Elliptical coils allow you to walk through fairly littered fields with a larger longitudinal size. Those. I provide greater search depth.
These reels also have greater coverage.

Coil applicability

Coils can only work with the metal detector for which they are intended. Those. If a coil was designed to work with a specific Garrett metal detector, it will not work with a metal detector from another manufacturer (for example, Minelab).
There are several reasons for this:

• discrepancy between the characteristics of mine detectors (for example, the Garrett ACE-250 metal detector operates at a frequency of 6.5 kHz, and the Fisher F75 at a frequency of 13 kHz. Of course, their coils are not interchangeable.)
• mismatch of connectors (All manufacturers install their connectors on the coil. That is, they have different diameters, with different numbers of pins, and the wiring in the connector is different)

Respectively,

• if you need coils for an AKA metal detector, then you need to look in the AKA coils section
• if you need coils for a Garrett metal detector, then you need to look in the section for Garrett
• coils for metal detectors 705, you need to look in the section for Minelab coils

But there are manufacturers of only coils (but not metal detectors). They produce sensors for various manufacturers. Here you need to carefully look at what devices these coils are intended for.
Examples of such manufacturers:

• Coiltek
• Detech

Reel prices

The price for a metal detector coil ranges from $100 to $300. On average, a reel costs $140.
The coil itself is considered a consumable item and requires replacement after some time. As a rule, its service life is 3-4 years. But maybe more (depending on how carefully you treat it).
But to extend its service life, protection is used on the coil, which protects it from mechanical damage (bottom and side). Over the course of two seasons, I tried several types of devices and reels, which I actually wanted to talk about.
Coils are divided into mono and DD, and the latter were called by professionals as the most preferable, because they have the best search properties - that’s what the old-timers said and I listened to everything.
In fact, and I’m no exception, all (well, almost all) search engines begin their search careers with metal detectors, which are equipped with mono coils as standard, so you don’t have to be particularly capricious - budget models come with mono coils.
Is this bad? No, it seems to me that it is with mono sensors that one should begin entering the world of metal detecting, since they have the capabilities and properties that help beginners quickly and efficiently learn search methods and start a successful career.
The first thing that is very pleasing about a mono coil is its stability. When working with them, you will not hear unnecessary sounds (for example, when the coil hits stems and roots), and even if the device has an adjustable ground balance, the coil behaves extremely quietly, reacting only to real metal targets, without creating phantoms.
The second quality, for which even advanced searchers have mono coils and there is no doubt about it, is the ability to very accurately determine the location of a target in the ground, that is, work in pinpointer mode.
This quality is especially important for beginners, as it is important to learn how to extract finds from the ground without harming them. The mono coil accurately shows the center of the target, and you don’t even have to dig large holes to easily dig up the found object.
The third quality, which is also valued by search engines, is lightness. Lightness determines how tired you will be during a day of searching; this is an important factor and here mono coils have no competitors yet.
But if mono coils have so many advantages, why do most advanced searchers prefer DD coils over them?
It’s simple - they also have many advantages, and if they lose in the qualities listed above, then in other, no less important ones, they will always be far ahead.
DD coils allow you to see the target deeper - this is already a confirmed fact, and with the same size as a mono coil, the increase in depth can be up to 30%, depending on the target.
In addition, DD coils are seen as a beam, and not as a hat-like parabola, so missing targets is eliminated and larger areas can be surveyed than with a mono coil.
Another good reason for choosing a DD sensor is the ability to work on waste sites, where to isolate the desired signal it is enough to simply approach the target from a different angle. With a mono coil, no matter what you say, all targets will still fall into its field at once.
This is how it works out, in theory. What in practice? Initially, I used metal detectors equipped only with mono sensors and was extremely pleased with them, I didn’t even plan to change to something else, but then I got a large DD coil and at the first exit I was pleased with excellent finds in a field that I considered hopelessly beaten!
It was all about the depth of the search and the width of the capture - where the mono coil did not reach the target, the new one easily recognized the object, and the time to pass one line across the field was reduced by almost half!
True, I was quite tired, since the coil weighed unusually a lot, and the earth stuck to it added weight, but it was a sensational discovery, after which the coil included in the metal detector kit was never used again.
The next DD coil was smaller than the first, which immediately affected less fatigue, but in search depth it was almost not behind its sister, so maneuverability improved and it became possible to confidently work in garbage areas, where the larger coil still did not work very correctly.
The problem with all DD format reels is poor alignment of the target, and if a hole is dug and the find remains in it, the situation does not matter. A separately purchased pinpointer helped me get out of this situation, which facilitates the process of searching for a target in the dump and in the hole, which, by the way, became much larger than those that I dug when working with a mono coil.
By increasing the search depth, the identification of finds has also improved. What was at the limit of the depth capabilities of mono sensors, the device often “carried” into the iron sector, but as soon as objects appeared in the zone of reliable reception, thanks to the increased search depth with the DD sensor, the signals became confidently colored, which means that useful signals began to pass through much more difficult.
There is one more fly in the ointment with DD coils - they are more expensive than single-size mono sensors, but I am sure that the money spent on them will be returned very quickly.

Among novice treasure hunters and just those who like to wander around with a metal detector from time to time, you can often hear arguments about which coil (sensor) is better. You hear so much in these disputes, people use their knowledge of physics, and some even begin to build some hypotheses.

I am not a physicist, and to be honest, during all the time I have been interested in this hobby (and this is not one or two years) I have not tried to delve into the physics of the processes taking place. By and large, the user does not need to know all the subtleties; it is enough to understand some basics and nuances.Of course, if you are passionate about electronics, if it is fundamentally important for you to know how a DD coil works, how the soil affects the radiation and perception of a signal, then, undoubtedly, you can set up various tests and take measurements, since hobby is hobby.

An ordinary digger is a person who works with maps, walks a lot, loves nature, and studies the history of his region. For him, a metal detector is just an additional tool, thanks to which he finds answers to his questions and assumptions. And if we talk about reels, then we can say with confidence that all the reels that are on the market are good! We can also say that MONO coils are no worse than DD coils, and vice versa. It's just that different types of coils are designed for different search conditions.

Map analysis is one of the foundations of a real search engine

About the advantages of MONO and DD coils

So, if you have a huge field in front of you, and you need to quickly walk through it in order to find out whether the place is worthy of attention or not, then preference in this case can be given to a DD coil with a larger diameter. This type of coil emits a rectangle, and at depth the beam does not narrow and is approximately equal to the width of the coil itself.

In other words, in a unit of time you will explore a larger area of ​​land with such a coil, and the likelihood of missing something will be minimal. But, if the field is littered (garbage metal), or, then you will have to dig with such a coil, since it will pick up nearby signals.

The beam of MONO coils narrows into a cone as it moves away from the surface of the coil, that is, at a certain depth, the coil will scan only a small area (the top of the triangle). With such a coil you need to drive more carefully, the search engine's step will be slower, and you need to make a deeper sweep of the coil on the previous pass (max).

Mono coil: general view

But this type of coils has its advantages: they very accurately show where the target is, and they are more convenient for working in “trash bins”. And if they lose a little in depth (and not on all soils, a lot depends on the search conditions and purpose), but they allow you to study the place in more detail.

In general, ideally, a treasure hunter should have experience working with both types of coils in order to draw a conclusion for himself which coil is more convenient for him. After all, in littered areas you can safely work with a DD coil; you just need to change the standard coil to a smaller coil.

General principle of operation of a DD coil

So, as you can see, although the coils differ in scanning methods, all this has little effect on the quality of search in capable hands. There are search engines who will never change their DD to MONO, there are also those who are used to working with MONO, they dig less holes, they like this type of search.

MONO and DD: choice of taste

Many search engines in a new place begin to work with a DD coil, and if the place is promising, mentally or in other ways they divide it into sectors and explore using MONO coils. Although, all this could be done with one coil of any type - it’s a matter of taste.

We can talk about the fact that coils of one type are somewhat lighter than their counterparts of another category, but we did not weigh them specifically, and the difference of a few grams (comparing coils of the same diameter) is not fundamental. Regarding the “noisiness” of the coils, we can say this: “If you search wisely and don’t hit the bricks with the coil, everything will be fine. If you hit the walls with a coil, there will be phantoms on any coil.”

What else can you say about coils? It should probably be added that a search engine should have at least two coils in its arsenal: one of smaller and one of larger diameter. Well, don't forget about. Otherwise, a lot depends on luck, luck and understanding of what and how you are doing.

Have you protected your reel?

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The first step is to understand the classification of coils, their purpose and the features of the device itself. The main difference between DD and Mono coils is the signal shape, which seriously affects the quality and direction of the search. But when changing it, the coil model and the device model must be compatible. Otherwise, serious interference may occur or the control unit may be damaged. You should not try on a hobbyist’s reel on your device if you are not sure of the compatibility of the devices. After all, the ability to replace the coil was made to make the metal detector cheaper to maintain, thanks to replacing only part of the device, or to allow targeted searches, by using special coils.

Classification by coil types.

Until recently, it was mono coils that came with the metal detector. They have a cone-shaped signal, which is better suited for spot searching or searching in contaminated areas. However, this type of signal covers a small amount of ground, and the swing for each step should overlap the previous one by about half. So at a depth of 10 centimeters, the diameter of the beam with a 9-inch coil is reduced by half, and at a depth of 20 centimeters it will be only 3-5 centimeters. Mono coils are best used after detecting a cluster of targets. This will reduce the area of ​​the cop and get a clearer picture of the alleged subject.
With the advent of DoubleD coils, search efficiency has increased several times, and the latest metal detectors are supplied with this type of coil. They got their name because of the mirror arrangement of the receiving and transmitting loops, reminiscent of two inverted letters “D”. The signal in the DD coils has the shape of a cylinder, which makes it possible to uniformly scan the area under the coil. This type of coil is ideal for highly mineralized soils and scanning large areas. But the difference between DD and mono coils is not the only criterion for improving your results.

The influence of coil size on search.

An effective instrument search must also take into account the size of the coil, which can vary from 4 to 20 inches (if necessary, coils up to two times larger can be found). Small diameter reels are popularly called “snipers”. The small size of the coils allows not only to scan areas in hard-to-reach places, but also to minimize the influence of soil mineralization. By searching at standard frequencies using a “sniper”, you can detect even the smallest objects and achieve an accurate determination of the material of nearby objects. The disadvantages of such coils include the high swing frequency of the device and the shallow search depth.

More versatile are medium coils ranging from 8 to 12 inches, capable of detecting a variety of targets. Coils larger than 13 inches in diameter are better suited for deep searches for large objects, but they often miss smaller objects. This is due to the need to analyze a large volume of soil and equate small objects to the earthen background. In addition, the weight of a large coil can exceed 1 kg, which will become a significant factor during many hours of searching.

Search direction depending on the coil frequency (kHz).

Having delved into the selection of coils in more detail, it is imperative to pay attention to their frequency. The frequency of operation is directly related to the quality and strength of the response from various targets. Amateur devices are most often capable of operating at a single frequency, but professional models with differentiated search frequencies can also be found on sale. The most optimal frequency is 6-7.5 kHz, which allows you to search for medium coins. It is suitable for most metal detectors. Coils with a frequency of 13 to 50 kHz are often used to search for small objects, jewelry and even gold nuggets. But the use of high frequencies significantly reduces the search depth due to the attenuation of electromagnetic wave oscillations. If the goal is to search for a large object at a depth of up to 1 meter, then you should pay attention to devices with an operating frequency of 3-4 kHz.

Coil shapes.

In addition to the technical component, the coils also differ in their shape. They can be rectangular, elliptical, round, or butterfly-shaped. If you take into account the fact that for each step the coil swings from side to side, then the length, not the width of the coil, will be more important. The number of swings depends on the length. Therefore, the elliptical shape is considered the most convenient, which greatly facilitates balancing of the coil. The round shape has now practically lost its relevance and is quite rare.

Comrades, especially those who are just starting to search with a metal detector, you will find more interesting tips in. I am a digger myself and collect everything useful there.

Welcome everyone to the blog about .
Today we’ll talk about coils for metal detectors, dd - coils. As you know, they come in 2 types - regular, round and elliptical. What exactly is the difference between these two coils, let's try to figure it out. Or is it still better to have both coils in the search engine’s arsenal at once? Using the example of a small 6" sniper coil and an ellipse.

The first difference between an ellipse and a round dd-coil is its lightness. The coil mounts, and this is a minus, are slightly smaller than those of a standard 10" dd coil. As experienced searchers say, it is better to search with an ellipse in heavily littered areas; with such a coil there are many times more finds. It is worth noting that, according to the principle of its operation, the ellipse coil is similar on the so-called sniper, a small DD coil measuring 6 inches. But the ellipse is much larger. It is more versatile, it can also be used to search in the field (with a sniper you will be crazy to walk in the field), at the same time, the ellipse has proven itself to be excellent in littered areas. Besides all These advantages of the ellipse can also be noted in the ease of use where there are bushes, branches, the coil is narrow and it is very convenient to stick it between the bushes.The penetration depth is many times greater than that of a sniper coil.

But if, nevertheless, the area is very littered with debris, then when searching there is no equal to the sniper, a round 6" coil. It is convenient for it to work even in other people’s holes, as a rule, the holes are larger in size than the coil itself, so you just stick the coil in someone else’s hole and you break through the walls, but again you lose in the depths, sniper hits too shallow. Although it is not intended for deep holes, but for searching on the surface.

One of the disadvantages of the ellipse is the coil mount. It takes a very long time to assemble, so digging professionals recommend immediately purchasing a separate lower rod, attaching the ellipse and not removing it anymore. When installing on a metal detector, simply replace the lower rod.

Well, another significant disadvantage of the ellipse is moisture intolerance. After just half an hour of work on wet grass, the reel begins to fill with glitchy trills. So keep in mind that you can cure it by strengthening the tightness of the bottom and edges.

The strong sensitivity of the ellipse also causes a lot of trouble, especially in the spring, when it hits dry stems of grass and burdock, the coil also begins to sing and fill.

So, to summarize everything, the ellipse is a coil that occupies a middle position among standard 10" round and 6" sniper coils. That is, if you decide to walk along a regular field, then your choice is a standard 10" dd coil; if the field is heavily littered, then ellipse. If you walk around one place where there is a lot of metal trash, but the place is promising, then use a sniper. Something like this. Of course, everyone decides for themselves where and what to go with, but extra information will not be superfluous. By the way, new ones came out recently