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DD Coil Center Receiving Shape Differences


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Hi all,

    I just ordered a NEL Thunder coil for my also new Notka Makro Simplex+. This coil has a straight shape center receiving area. Other coils have a football (American type) shaped receiving area. I can't find any discussion on these two types of constructions. 

   Does anyone know what each shape does? Like specifically, bennifits and differences? I can only speculate as I'm not very knowledgeable on this. I am thinking the NEL Thunder may have even sensing front to rear, and maybe narrower field which may be able to separate slightly better. 

    The football shape coils I am thinking, may have a different field shape and may do something different. All this is speculation. However, it is this Thunder coil that is different than most and I'm curious as to what this coil does in it's detection field. 

   For me, the coil has a lighter weight and larger area than other options. I'm searching dry sand and open park areas. Maybe even waist deep water.  This shape and size is ideal for me. And the construction is new to me, just so you know. Thanks! TG

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  • Steve Herschbach changed the title to DD Coil Center Receiving Shape Differences

Great! This info helps. I see it's a transformer rather than an antenna.

   My question is about the shape of the detection field. For instance, a concentric field is different than a DD field. How the field changes seems to be the shape position of the two windings and the way they overlap. The Thunder coil has 2 straight areas overlapping while the others have a football shaped overlapping area. Some advertising said the larger overlap area gives greator detection area. I'm thinking, the pointed areas top and bottom are then smaller detection areas. Maybe then, the Thunder coil has a consistent size detection area front to back? It mat be that only close targets are affected by the different shapes. I'm just wondering why all coils arent made like the Thunder. It simply seems more logical to make the detecting area consistant. The footbal detection shape is only the largest in the center. 

Here's photos of these two examples.1822697464_813RB1lPFL._AC_SL1500_.thumb.jpg.5e81638f3b9ec8004683ee61a51b48d2.jpg81yk4muXafL._AC_SL1500_.thumb.jpg.b18d7d5e4901f0647cd0dfabf757d2b7.jpg

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The internal windings are not necessarily perfectly centered in the housing, so they may be more similar than you think. I’d be very surprised if it makes a difference you could genuinely discern in normal use.

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The Thunder and Storm are the only ones they made that look like that, and with the SuperFly being their latest coil design they went back to the more rounded Tornado winding look. 

38180676_Nelsuperfly.thumb.gif.438fa7dcc03386adb99c25416a0f99b5.gif

I don't have a Superfly, I ordered one ages ago but it was lost in the post so I never reordered it and just got the refund, I do love my Tornado though, great coil that one.  I'd be interesting in what you think of the Thunder, it seems a bit of a stock coil alternative more than anything.  It'd be good to hear how it goes on the Simplex as I'm still considering buying an alternative coil for my Simplex to try improve it's Target ID capabilities if possible.

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...I found one of the information about the differences in the winding in the information about the coil 12X10 SEF .... ,, because I was also interested in the extent to which the straight versus oval inner area of the coil winding can affect the target detection :

12×10″ SEF Pro Coil

The 10 x 12″ S.E.F coil is designed to go deeper and offer better all around performance when compared to the other “DD” coils on the market today. Better ground balancing, more stable operation, more accurate pinpointing and increased target identification are all benefits of this coil. Field Tests show this coil truly finds deeper targets.


SEF%20Coil%20Expanded%20Area%20Diagram.png

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3 hours ago, Steve Herschbach said:

The internal windings are not necessarily perfectly centered in the housing, so they may be more similar than you think. I’d be very surprised if it makes a difference you could genuinely discern in normal use.

I see what you mean Steve. I my case, I am not looking for more depth. I am looking for more ground coverage. 

   I'm using it on beaches looking for recent drops. Miles of beach as you know. I am hoping for an even area of detection front to back. If you notice on the Thunder, the center crosses in the very front. The other design actually looses detection length in the middle. The thunder is 14.5 inches in the middle. And, the Simplex+ SP28 stock 11" coil is only about 9" down the middle. I'll be gaining 5" in the middle. That is about a 50% increase in coverage. So, my hope is that it has consistent detection front to back. 

   Also, I believe, having a more narrow center may be better at separation and may be less prone to masking. I'm curious about that.

The price was right, and the weight is less than the 13" Notka Makro has for the simplex. I'll give it some testing to see how it works. I had to send it back as it was dead on arrival. They will be checking the next one before shipping. So, I'm waiting...

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10 hours ago, EL NINO77 said:

...I found one of the information about the differences in the winding in the information about the coil 12X10 SEF .... ,, because I was also interested in the extent to which the straight versus oval inner area of the coil winding can affect the target detection :

12×10″ SEF Pro Coil

The 10 x 12″ S.E.F coil is designed to go deeper and offer better all around performance when compared to the other “DD” coils on the market today. Better ground balancing, more stable operation, more accurate pinpointing and increased target identification are all benefits of this coil. Field Tests show this coil truly finds deeper targets.


SEF%20Coil%20Expanded%20Area%20Diagram.png

This was what I suspected on the detection area. I won't call it a field any more as I now know better! 

   The shape on the left shows a narrower area. This is what I am thinking of the Thundre's area shape. A thinner line which hopefully separates better and has less masking. I find spots with bottle caps, foil and coins. The Simplex+with the 3 tones is great at deciphering what is down there. Just as long as those items are not masked. If indeed it has the thin detection area, this coil may be the ticket!

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Just remember that’s marketing information, which often is disconnected from reality.

One coil transmits, the other receives. In general it’s the receive side that matters. The transmit side excites the target, the receiver side detects the effect. So another generality is that the closer an object is to both the transmit and receiver coils, the smaller the item can be and still be detected. Expanding the distance opens it up to the question of whether the item is closer to the transmit coil, or the receiver coil. In either case small target sensitivity is decreased, but ground effects alleviated at the same time. More depth on larger items can also result. A two box detector is a setup where the two coils have been entirely separated, and now only very large targets signal, but at possibly much greater depth.

But again, in this case, as far as ground coverage, the difference is minimal, and can simply be measured with a ruler, and the distance between the crossover point at each end of the coil. I personally prefer to compare and own coils that truly have widely differing characteristics, as when coils are very similar the benefits going one way or the other are minimal. Boils down to picking the one you like best, and getting in with business. The quality of the location, and hours spent detecting, will decide your success, not something as hair splitting as this. Or at least that’s just how I look at stuff like this.

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15 minutes ago, Steve Herschbach said:

Just remember that’s marketing information, which often is disconnected from reality.

One coil transmits, the other receives. In general it’s the receive side that matters. The transmit side excites the target, the receiver side detects the effect. So another generality is that the closer an object is to both the transmit and receiver coils, the smaller the item can be and still be detected. Expanding the distance opens it up to the question of whether the item is closer to the transmit coil, or the receiver coil. In either case small target sensitivity is decreased, but ground effects alleviated at the same time. More depth on larger items can also result. A two box detector is a setup where the two coils have been entirely separated, and now only very large targets signal, but at possibly much greater depth.

But again, in this case, as far as ground coverage, the difference is quite minimal, and can simply be measured with a ruler, and the distance between the crossover point at each end of the coil.

Ok Thanks Steve. I get that one side is transmitting and the other is receiving. The thing that I'm not clear on, is the talk about the middle. One shape has the larger middle opening which supposedly gives a larger detection area in the middle. Another narrower opening says its a narrower detection area. So, even though the one side receives, they're saying it's the middle that recieves. That's where I don't get it. 

   Also, yes, the Thunder is the coil I picked for it's length up the middle. I'm not expecting to get any difference in depth. I have the GR40 for the Gold Racer. It's big, I like it and it works well. That's what convinced me to get a larger coil for the Simplex+. However, the Thunder coil had almost the same middle coverage in a smaller lighter coil. The key for me is coverage. The smaller middle opening is a still to be a tested thing. Maybe I'll test both the GR40 and the Thunder to see if there's something different going on. I'm hoping. 

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