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VLF Concentric Vs DD Coils


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On 1/26/2015 at 2:38 PM, Jonathan Porter said:

Manufacturers are afraid of negative feedback from customers complaining about noise so opt for the soft solution of providing DD coils only!! Case of not understanding what is required to be effective when searching for gold or worse trying to do too much at once.

If the GB II, an outdated design, can do it effectively and IMHO MUCH quieter than the GB PRO with its DD coil and lower FREQ, why can't the more modern offerings, especially with the benefit of reasonable auto tracking features, be able to do it? 

How bout giving me a GB II in a modern GB PRO housing with a concentric coil and Minelab auto ground tracking with three frequencies say 19Khz, 32Khz and 70Khz? 

JP

Maybe it would be a good Idea to supply machines with the Coil as per Customer Choice at the Time Of sale, This would save you having to buy an extra coil at the Time Of Purchase. and If A Person did want extra coils that's what the machine would come with Instead Of being stuck with a coil that you wont use.

The Companies will Listen to people Like You and Steve, but Convincing them is the Hard Part,

John

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  • 1 year later...

  • 3 months later...

 

From my observations and also the measurement of mineralization -may say from a medium-sized 23x20cm CC coil it shows 2x a higher mineralization value as well as a 23x20cm DD coil.

When comparing dimensionally larger CC and DD coils, I feel the differences will be even more important ..

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22 minutes ago, EL NINO77 said:

 

From my observations and also the measurement of mineralization -may say from a medium-sized 23x20cm CC coil it shows 2x a higher mineralization value as well as a 23x20cm DD coil.

When comparing dimensionally larger CC and DD coils, I feel the differences will be even more important ..

In my ground I have not seen any major changes between the 2 types of coils, The only thing I have seen is I tend to get more Iron and crown caps ID'd as good targets with a DD  and the Etrac with it's DD was all over the place, giving up to 9 or 10 different sets of figures for crown caps, The Sovereign GT was really good when it came to IDing things and having the meter on it helped a bit on targets that were a bit iffy, The only down side to it was the very slow recovery speed.

Most of my ground measures between 57 and 67 on the GND on the MXT and pulling coins from over a foot deep is quite common using the 950 coil and using the 12"/300mm Coil can be seriously Deep, being old Farm land that has seen every thing from modern man back to the Neolithic there is a lot of Iron junk down there so a Concentric and a fast recovery seems to work best even using the 12" Concentric it still sniffs out the keepers.

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  • 7 months later...

Was reading all the incredible info in this old thread regarding coil differences...so I have a question:

For underwater salt conditions, if you had a 7'' concentric, and a 9.5''x5'' DD eliptical....which one would you use? (as you see both coils are small, but that fits me for snorkelling much more than a larger coil)

I think depth wise would be almost the same (maybe concentric would be deeper)....but I also think that the 7'' concentric will be more sensitive to small gold vs the 9.5''x5'' DD coil. However:

- Will the 7'' concentric handle salt underwater conditions, since concentrics are more affected from difficut grounds?

- Which will have the greater real coverage area under the coil, regarding their transmition "shape"?

Which one would you choose and why? I read all the info here but still a little confused for what to choose for underwater-salt use...concentric or DD?

Thanks

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I'd try them both and see which worked better. What happens next depends on the detector. Theory is nice guide, but never replaces actual comparative tests with your own detector and coil, on your own ground. If I simply had to choose one without knowing which is best, I'd go with the DD first due to the ground canceling capability that tends to be inherent in DD coils.

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Thanks Steve, nothing compares to real time testing, so I completely agree.

I'm thinking of pulling the trigger for a Multi Kruzer for shallow underwater use (instead of risking again with my Nox 800 which drowned and got fixed)....I've found an offer from a Makro dealer who offers me one additional Multi Kruzer's coil for free in the package (stock is 11''x7'' DD...and he offers as an extra for free either a 9.5''x5'' DD, or a 7'' concentric)...so I was trying to decide which one should I choose as best for underwater in salt (I need a small one anyways). 

I think I'll choose the small DD....must be a safer option

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Salt water I have found the narrower dd more stable than a wider one and a dd in general more stable than a concentric. Comparing the 2 DD's I have for my Multi Kruzer the stock 7x11 is a little more stable towards the wet sand and doesn't false when hit with the surf but the 12" is deeper for beach combing. It does false when hit with the waves but that could very well be from the coil cover having water trapped behind it.

Having a smaller concentric for the Multi Kruzer is really good when you have a lot of flat iron like washers, steel bottle caps etc in trashy parks where they will come in closer to the iron range. DD coils will ring in flat iron up in the higher numbers but not all is lost if you keep iron audio on you can use the nose or heal of a dd to see if you get that really awesome grunt iron makes.

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13 minutes ago, kac said:

Salt water I have found the narrower dd more stable than a wider one and a dd in general more stable than a concentric. Comparing the 2 DD's I have for my Multi Kruzer the stock 7x11 is a little more stable towards the wet sand and doesn't false when hit with the surf but the 12" is deeper for beach combing. It does false when hit with the waves but that could very well be from the coil cover having water trapped behind it.

Having a smaller concentric for the Multi Kruzer is really good when you have a lot of flat iron like washers, steel bottle caps etc in trashy parks where they will come in closer to the iron range. DD coils will ring in flat iron up in the higher numbers but not all is lost if you keep iron audio on you can use the nose or heal of a dd to see if you get that really awesome grunt iron makes.

Many thanks Kac, that's what I was looking for...! Since I have the option for an extra free coil from the dealer, I'll go with the smaller DD for salt water use. Later I may add a concentric also for the reasons you mentioned when inland.

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Will the dealer swap that coil out for waterproof headphones?

Note on the Nokta waterproof headphones you need to crank the audio to 10 to hear it. Waterproof headphones in general have poor audio because of the speaker type.

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