MONO coil for AKA metal detector test

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MONO coil for AKA metal detector test, MONO coil for AKA metal detector test
 

Hello for everybody interested in AKA devices. Today i will be testing 8 inch 20 kiloHertz mono coil. Let me explain the situation. This area contains a lot of metal scrap. But a lot of finds were made here. For about a year this place was swept again and again. I just finished sweeping it with 13 inch 13 kiloHertz coil and now i will use 8 inch mono coil. Of course chances of finding anything here a pretty thin, because the area is searched many times before, and also the ground is covered with very thick layer of leaves. This mono coil is designed for working among scrap, it has pretty low search depth, but it can tell targets apart pretty good. And i am about to test HOW good actually.

Here is a first small result - a pellet. Nothing of interest by itself, but now i am sure this coil tells targets apart much better than the previous one.

With mono coil it doesn’t matter from which side you approach the target.

Guys, I’m getting curious what i might find. Because there are almost no non-ferrous signals left. Here is a second find - a button.

Here is something to sum it up. When I used 13 kiloHertz coil, i got much more iron signals. And i decided to go to the place where there were the most of them. But now with this coil i kinda lost my view on the area, because now i get much less iron signals. Partially because of lower search depths. But still there are some results.

Hello dear colleagues. Today we will film a short video considering metal scrap. Some kind of sport-like competition video with nail-board, which became some kind of international standard and a stack of coins. The contestant is AKA Signum 7272mfd with firmware version 2.06. The device is pretty old, it’s about 9 years old. Maybe 8, but I am almost sure it’s 9. No customization is done to it except for external power source socket. It is for using external battery when working in turbo mode for a long periods of time. Sometimes i needed it. The coil currently attached is 8 inch concentric mono coil. And we are going to test it.

So, let's quickly check the device settings. ST is set to 11, RT is set to 8, but its volume is set down to 1, because we are working in a room. Program number 3, the mode is set to metal scrap, the speed is set to 4. Economy mode is on, electric current is twice as low than in a usual mode. Simple math: turbo mode makes current twice as high, economy makes it twice as low.
Settings. Overall gain is set to 3, it is approximately 26 cm distance for a small coin detection, so sensitivity is high enough for us. You can see the frequency yourself.
Next is a very important setting you can play around with. But we are not going to. It is Iron threshold, and it is set to factory default which is 14. So nothing changed here, everything is standard.

So, nailboard with ho coins. I apologize for those signals i get while waving the device around. There a lot of object like heaters in the room. It is possible to randomly get phantom non-ferrous signal. But it does not become a problem. Let’s try getting it again. Yeah, somewhere around here.
Now, let’s put a target in there. The target is 2 penny USSR coin. I will not comment much from now on, you can see everything by yourself. Just in case.
Position number two.
It is possible to find, but easy to miss too. So this combination of target and device is failed. Which makes it one fail out of 8.

Next target is a stack of coins. The infamous type of target that is argued much about. The thing about this stack is that most devices detect it only when it is positioned like that. In this and this position it is detected as iron. It happens only with DD coils. If u use mono coil on any device this stack will be detected regardless of its position or device frequency. When using DD coil, there are some chance to detect the stack on lower frequencies. On high frequencies there is no chance. So depending on devices algorithm, somewhere about 3 or 5 kiloHertz will give you chance to detect it. Everything above 10 kiloHertz will almost always detect it as iron. Since we are using mono coil, we will have no problem with that. It is detected in any position.

I’ve got pretty obvious question asked on one of forums. You get something - you lose something, so how are things with this coil considering target identification in the ground? It is widely known and completely true that mono coils have much worse deep target identification than DD coils. It is easily explained with simple physics. For mono or concentric coil the ground signal is much stronger than it is for DD coil. So the very same ground can be a clear and easy one for DD and tough for Mono coil. So at certain target depth, whet its signal becomes weaker than ground signal, it will be detected as iron by mono coil. At the same time the same target can be visible as non-ferrous for DD coil.
It is relevant for high-signal types of ground. In the areas I work in this difference can show itself only in cases of really deep or small targets. At the same time, in scrap-filled areas this doesn’t mean much, because there is no chance to find deep-lying target anyway. Only by some amount of random luck.
I was asked one particular question. What will this coil detect under a brick? Well, we have a brick here. Looks bricky enough for me. And it definitely makes signal strong enough, stronger than most grounds. Times stronger.
I am balancing my device on this brick.
Here you can see i am getting signals from it. I get some phantom detections.
Now let’s put our coin under it. Well, no problem. There is no point in testing it from transverse direction. With any device like Equinox or E-track that work good with ground signals, brick will give you an iron signal from transverse direction.
Simple physics again: when a coil gets closer to a brick the ground signal suddenly becomes much stronger, peaks and gets lower just as fast. Simultaneously covering the signal of a coin underneath. This sudden signal peak is what makes it look iron.
You can call it some kind of rough arable land imitation. That is why in areas of arable land it is possible to find only objects that are not deep. Anything deep is detected as iron. Because of these sudden peaks of ground signal. This way it is detected though.
Let’s try it with smaller 1 penny coin.

The graphs are awful already, as if it was a tin can, but thanks to clear signal we are still able to identify it as a good non-ferrous target. Looks like it’s time to finish our test.
But you know what. Let’s improvise a bit.
It’s not like i am sure about it. But why not.
Let’s see what we get with nail-board and about 6 or 7 cm of high-signal ground.
Very good!
And to be sure we are not fooling ourselves and also you. Let’s test it without a coin.
No everything seems fine.
There are some phantom detections. So chances are high that in a ground like that you will have to dig for nails as well. But still there are no clear crisp signal.
Again.

Not bad, not bad.

Not that good. Well, if you know the ground is tough you may suppose that it is a target. But it still looks a lot like iron. I will consider it a fail. This position is a fail.
Clear. Position 4 will definitely be a dead one. It was dead even without a brick.
Yeah, dead.

Just cause we started. A stack of coins under a brick. The target is big, so now it doesn’t matter in which direction you sweep. Peak signal from the brick is still lower than the target signal.
No problem again.

I think we are done now. Filmed even more than we initially planned.

So, dear colleagues. We will be waiting for responses with your tests of different devices. It is currently winter, nothing to do for us, so why not use some spare time for these experiments. It will be interesting to see how well will other devices do in a setting like that. Just as i said, some kind of competition.
Now let us finish. We’ll be waiting for your test results. I wish you all an early spring, not just early but also a long one, so you can enjoy searching with no mosquitos, flies and other stuff like grass. And good luck in an upcoming season! Good bye.
Mongol
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