How get more depth??

4helements

Jr. Member
Oct 21, 2013
21
3
middle of Italy
Detector(s) used
Garrett 250 & Exc. 10"
Primary Interest:
All Treasure Hunting
Upvote 0
put a Watts coil on your detector, that should give you another 12"
 

As Ron said the 15" WOT, 13" Ultimate or 15x12 SEF will increase depth but there are trade offs with these like weight, more drag and less stable in water. Hunting in PP mode gives quite a bit more depth also with the stock coil. The PP and headphone mod that OBN does makes the Excal a whole different machine. He sales the kit if you are capable of soldering, it's quite easy to do yourself because it's all ode from the too endcap side. I use the stock 10" tornado and pick up targets deeper than I can dig in wet sand.
 

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Why would increasing the diameter of the search coil increase your detection depth?
It makes no sense from a physics point of view as you have to search a larger surface area under the coil
without an increase in power from your detector.


As Ron said the 15" WOT, 13" Ultimate or 15x12 SEF will increase depth but there are trade offs with these like weight, more drag in water, and more unstable in water. Hunting in PP mode gives quite a bit more depth also with the stock coil. The PP and headphone mod that OBN does makes the Excal a whole different machine. He sales the kit if you are capable of soldering, it's quite easy to do yourself because it's all ode from the too endcap side. I use the stock 10" tornado and pick up targets deeper than I can dig in wet sand.
 

CZ21 in all metal like I do - I get goodies down 2 feet
 

Why would increasing the diameter of the search coil increase your detection depth?

It's a trade off. The larger coil generates a larger magnetic field that penetrates deeper but with less field density - the power output is the same as a smaller coil. Less field lines means less sensitivity but greater depth.
 

It's a trade off. The larger coil generates a larger magnetic field that penetrates deeper but with less field density - the power output is the same as a smaller coil. Less field lines means less sensitivity but greater depth.
Jackalope, I think Sir Gala was pulling our leg about larger coil physics.
 

Fletch: I am very serious in obtaining an explanation as to why increasing the diameter of a search coil increases the depth a target could be detected at with the same detector.
Under the field conditions that I hunt under, I have not noticed a drop off in depth using a smaller coil.
Jackalope, I think Sir Gala was pulling our leg about larger coil physics.
 

Sir Gala Clad, This has been covered many times on every forum on the net. Search TNet or google it and you can read dozens of different explanations on the physics involved. I did find this one particularly interesting from one of the founders of Minelab. Yes I confess to being brand loyal. Most of the time your exactly right an 8-11" coil will give plenty if depth and coverage for the average coinshoot or relic hunt, but on wide open beaches or fields I like a larger coil mostly for more coverage, but also more depth.
https://www.minelab.com/__files/f/11043/METAL%20DETECTOR%20BASICS%20AND%20THEORY.pdf
 

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Under the field conditions that I hunt under, I have not noticed a drop off in depth using a smaller coil.

You may not notice it operationally, especially in iron soil that is attenuating the signal of the larger coil more than the smaller. But, the physics are the physics, which means the larger coil will drive deeper (all things being equal) but not have the sensitivity (to small targets) that the smaller coil will have. Most coin hunters are happy with getting coins at 7-9", which is within the range of most small coils, especially concentric coils in lightly mineralized soil. Within heavy junk and iron litter, the small coil will likely get the same depth with better sensitivity than the larger coil. At the beach, in light-moderate mineralization, the larger coil is going to get that deeper coin or ring, while missing the smaller jewelry and small iron trash. It's always a trade-off with physical laws.

Jackalope
 

I sure am glad I have a pulse induction machine..
 

Jackalope: What I am trying to determine is why increasing the size of the search loop increases detection depth. I suspect that a large part/ most of the answer is that larger coil size(s) allow further separation of the transmit coil from the receive coil which widens and deepens the detection field.

This also explains why increasing the coil size of a monopulse coil (same coil is used for transmitting and receiving) used on Pulse Induction Detectors significantly increases your ground coverage with little if any increase in depth capability.

You may not notice it operationally, especially in iron soil that is attenuating the signal of the larger coil more than the smaller. But, the physics are the physics, which means the larger coil will drive deeper (all things being equal) but not have the sensitivity (to small targets) that the smaller coil will have. Most coin hunters are happy with getting coins at 7-9", which is within the range of most small coils, especially concentric coils in lightly mineralized soil. Within heavy junk and iron litter, the small coil will likely get the same depth with better sensitivity than the larger coil. At the beach, in light-moderate mineralization, the larger coil is going to get that deeper coin or ring, while missing the smaller jewelry and small iron trash. It's always a trade-off with physical laws.

Jackalope
 

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Yeah Just like in the Danced All Night Lyrics from My Fair Lady with a few changes for detecting:

My head's too light to try to set my Sea Hunter down! Sleep! Sleep!
I couldn't sleep tonight.
Not for all the jewels in the crown!
I could have dug all night!
I could have dug all night!
And still have begged for more.
I could have spread my wings
And done a thousand things I've never done before.
I'll never know What made it so exciting;
Why all at once My heart took flight. I only know when he
Began to dig with me I could have dug,
dug, dug all night with my Sea Hunter till my arms fell off!


Just get a SeaHunter and dig till your arm falls off
 

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