new coil idea. ...

[KCK]

I have this idea in my head. I can't seem to shake it. I want to design a coil with a switch on the detector that allows for the standard double D coil in one position and a concentric 3-4" coil in the second position. May work well on an AT PRO? Any body do any coil work of their own out there? Or know of any designs where a dual coil is being developed or tested.

 

[Muddyshoes]

Welcome to the 1960s and early 70s!

Garrett used to have that as part of their BFO metal detector. It was two coils in one, with either the large coil or the smaller coil being selectable with a toggle switch. One of those, a 1960s model, just closed on eBay.

http://cgi.ebay.com/Vintage-Garrett-Hunter-Metal-DETECTOR-6-12-1960S-/280695410436?pt=LH_DefaultDomain_0&hash=item415ac00f04

The pictures below are from my 1980 Garrett Catalog.

 

[ralph]

I think that idea is still relivent, say a 10 in concentric(for covering ground) with a 6x8 dd in the middle(for trashy areas) switchable with a toggle switch. Only drawback would be weight, but done as a printed coil weight would be fine.

 

[G. E. Edwards]

I wonder how the coils don't hear each others wires? Or am I way behind in technology? Gene

 

[KCK]

Checked out the BFO coil.......Thanks for everyones reply. I used to be on a forum that George Payne had years ago. We all discussed some of these ideas but never went anywhere with it. I know our old 4 and 6 inch coils were great on pinpoint! But I don't want to go back to the freakin 60's hahaha

KCK/OHIO

 

[KCK]

Interesting! Thanks

 

[dahut]

How do you put a DD and concentric coil together?
The two designs are mutually exclusive aren't they?

 

[ralph]

That is why there needs to be a switch, to switch from concentris tx and recieve to ths dd tx and recieve. In the search mode the coil not being used wouldnt register because there would be no movement between the 2 sets of windings. In pinpoint there would have to be some special positioning to null the unused windings.

 

[ralph]

not if they are different sizes.

 

[dahut]

not if they are different sizes.

The name "double D" implies the configuration - two D-shaped coils, with the long, straight sides overlapped, back to back.
Concentric on the other hand, is essentially two coil windings, one inside the other. The outer is the field winding, the inner the phase shift detect winding (They dont actually send and receive signals - only PI's do that).
If the thinking is that they only need to be placed one over the other, and then switched back and forth, they would interfere with one another.
Now you could, in theory, place a receive coil inside one of the "D" shaped coils. The latter would be the field coil. But they would be off center, for one and NOT concentric for another.
I don't see that it is possible, as I understand these things.

 

[dahut]

not if they are different sizes.

The name "double D" implies the configuration - two D-shaped coils, with the long, straight sides overlapped, back to back.
Concentric on the other hand, is essentially two coil windings, one inside the other. The outer is the field winding, the inner the phase shift detect winding (They dont actually send and receive signals - only PI's do that).
If the thinking is that they only need to be placed one over the other, and then switched back and forth, they would interfere with one another.
Now you could, in theory, place a receive coil inside one of the "D" shaped coils. The latter would be the field coil. But they would be off center, for one and NOT concentric for another.
I don't see that it is possible, as I understand these things. It isn't about our desire to do such a thing, but a function of electrophysics that prevents it.

 

[Muddyshoes]

I'm a 1950s science fiction "B" movie freak, and I can tell you with 100% certainty that the wiring problems of having a combination "DD" and concentric coil can be overcome by simply using Atomic Energy and the kit below:

- Muddyshoes

 

[dahut]

I'm a 1950s science fiction "B" movie freak, and I can tell you with 100% certainty that the wiring problems of having a combination "DD" and concentric coil can be overcome by simply using Atomic Energy and the kit below:

- Muddyshoes

Of course, silly me. All things are possible with atomic energy.