"Dual field" coil?

Has anyone ever thought of a 'dual field' coil? Like a detector, with as an example, an 11" coil with a 5 1/2" coil inside the 11" coil. the detector would have a switch/button to change between the 11" and 5 1/2" coil.
Coil weight would be a concern but the benefits of such an arrangement speaks for itself.

Garrett did it back in the 60's



But the trick is it was a B.F.O. detector...you could switch back and forth with a selector switch big coil and little coil with the flip of the switch...The small coil is the round one on the toe of the bigger coil's in the pic's...

Its also doable on a Pulse machine they actually run dual sizes in unison on a T.D.I.

but those 2 trasmissions methods are very similar in that one coil winding is all that is required......not like a modern V.L.F. that uses a transmit and recive coil..the B.F.O. used one coil winding , as does the Pulse machine's...

V.l.F. is continuous trasnmit and continuous recieve so adding another coil into the same coil housing would have very hectic result's by using the winding's
method..

there could be other ways to get things achieved...Maybe in the future...But in the future why is a coil going to be needed?

Keith



Edited 1 time(s). Last edit at 10/26/2012 12:07AM by Keith Southern.

Thanks Keith! My old Relco BFO only had a 1 coil setup... I got screwed!
Seriously though, we put a man on the moon and rovers on Mars... and smart phones in our pockets. Surely a dual coil for VLFs could be designed.

Terry

I didn't know that about those old BFOs, that's pretty cool tech for that era
Thanks Keith

Flip of the toggle and change coils a nifty idea....would feel windings of one would affect the other but properly shielded ???

As far as Charles Garrett he had some great ideas along the way and they still keep coming....and his units produce some nice finds...

I've been learning my TDI with dual field coils. It come stock with a 12" dual field coil that has both a 12" loop and a 6" loop in series. Both coils are active. One more sensitive to larger items, one more sensitive to smaller items. It also seems to me that the smaller loop is more sensitive to ground signals than the larger loop. I would think that the next logical step in TDI development would include the ability to turn off one or the other loop as it might be needed for site conditions. But it seems the key word in the TDI dual field loops is "in series". Apparently, because the two loops are wired in series, it is not currently possible to turn one particular loop on and off. :shrug:

HH
Mike

Yes if you turned one loop off Mike I believe you would have problems on the T.D.I.The other coil winding would cause problems or at least be detrimental to full performance...

Keith