I Don`t Understand What Minelab Is Doing

[Steve Herschbach]

On 8/18/2019 at 10:02 PM, Steve Herschbach said:

It’s not a “Minelab Outing”.

 

Late breaking news - it is possible the new Minelab Vanquish will be on hand.

[mn90403]

I would rather they have the new small coil for the GPZ.  But I'm going to ask them about the Equinox update and ...

[Steve Herschbach]

Don't forget the 7" x 10" for Equinox. In fact all three Vanquish coils should be made available to Equinox owners!

[Lacky]

That prompts me to ask...is there any advantage to having a round DD coil? Since the main detecting area is where the coils overlap isn't a round coil just wasted material?

Honest question,  so if there are advantages please explain. I dont pretend to understand the specifics of coil design.

Edit to add, my Lobo came with a round concentric (or a bought separately,  can't remember)  and an oval DD, so I just kinda assumed that was the shape of DD coils up till I bought the equinox. 

[Steve Herschbach]

In theory a round coil is the best design. If comparing depth you should measure an elliptical at the narrow spot, not by length, when comparing to around coil, to get a fairly good idea of which will go deeper. In other words, a 10” round coil gets more depth than a 10” elliptical coil. Some people also like to calculate square inches of area for comparative purposes. But generally a 7” x 10” coil acts more like a stretched 7” coil than a 10” round coil. Which is why I usually list the narrow diameter first when discussing elliptical coils just to emphasize that point.

Ellipticals came about mainly for nugget hunters, who like to cover larger areas but who also need to poke into nooks and crannies. The concept spread to other uses from there.

[Lacky]

So basically the round coil broadcasts a larger field that penetrates deeper?

Edit-wouldnt that mean the bigfoot type coils, long and skinny, would suck at depth, or do those follow different rules?

[Steve Herschbach]

58 minutes ago, Lacky said:

So basically the round coil broadcasts a larger field that penetrates deeper?

Edit-wouldnt that mean the bigfoot type coils, long and skinny, would suck at depth, or do those follow different rules?

Absolutely, when compared to an 18” round coil a Bigfoot coil sucks for depth in milder ground. In high mineral ground the difference is less severe. I love my Bigfoot for ground coverage, not for the depth. The depth is not bad - the length does add some... the square inches thing at work, but nowhere near what is possible with an 18” round.

Coil Basics by Carl Moreland

About Search Coils by Dave Johnson

Search Coil Field Shape by Dave Johnson

[Jonathan Porter]

I'm more interested in the receive area of the coil, obviously with the larger coils less winds to the get inductance right equals quieter operation over high mineral ground, so a bigger coil will be less sensitive to near to coil variations (which is also an advantage) but in essence the size of the receive area, especially if that receive area is round in the case of Mono coils, provides a better outcome compared to odd shaped windings. 

The key is to get the very center of the receive winding over the target plume (that's the field created by the target that radiates out evenly all around and away gradually becoming equally weaker and weaker over distance). With the GPZ because of its dual receive its VERY important to keep those two receive windings in unison with each other, that means not tilting one receive winding into towards the ground (this will mean the other receive will be being pulled away from the ground at the same time) which can create varying degrees of saturation signal with the other side also potentially generating some degree of salt signal. 

JP

 

[mn90403]

JP,

Are we throwing things 'off' when we turn the coil on edge to pinpoint?

Mitchel