New coil design

[dbanner]

Concentric coils are a pain to make, if only because of balancing with bucking coil and small loop wire. Etc, etc.
Not to mention back and forth with adding/ subtracting turns etc.
Anyone who has ever made concentric coplanar search coil design knows what I speak about. Calculated values on paper will only get you in the ballpark, actual measurements are required for getting the thing properly nulled at correct frequency etc etc.

[dbanner]

Also, contrary to what some people think, the Rx coil need not be in the centre.

[dbanner]

Anyways, the design I had in mind goes like this.
Tx and Rx coils follow normal coplanar design, difference is that there are two bucking coils which are each half the diameter of the Rx coil. The two bucking coils are placed opposite each other, half way on either side of Rx coil overlapping it. Now fine balancing can be achieved without small loop simple by small adjustments of the overlapping bucking coils. No need to add or remove turns on bucking coils since cancellation is achieved by moving bucking coils across Rx coil, see?
I'll draw small sketch to illustrate.

[dbanner]

better yet, here is photo.

[6666]

What are you using it on ?

[dbanner]

No, no. This is from a relic Magnum detector. But it shows a practical design in use. Therefore it does work. I wanted to make one to see if it's any good. Even though there is bit more work to wind coils, fine balancing would be a simple procedure, given the two trim resistors as shown. No fiddling with loop wire.
Also, this arrangement would make it easy to null either side of deepest null by simply turning a screw.
Problem is that no info on relative diameters of the various coils and turns ratio of bucking coils to TX etc. But I think it's worth exploring. The bucking coils and tx coil are all connected in series, the bucking coils wound in opposite directions to tx. Both tx and Rx wound in same direction.
So long as you figure out the parameters, reproducing them would be a straightforward thing.
The nice thing is that you just wind four circular coils with predetermined number of turns and assemble them as shown, bringing Rx close to null, then fine tune with trimmers. Easy. No adding or removing turns then fiddling with loop and simultaneously increasing decreasing cap values.

[waltr]

Interesting idea.
I would like to see a schematic of the balancing/nulling resistor arraignment.

I do use a 'standard' concentric on my HH PI. Was not hard to make or to obtain a null.
The trick is to have a little extra wire from the buck coil to the TX coil. Then just move the extra wire, open/close loop, to obtain null.

[dgm]

Hi dbanner, I wanted to ask you to lock the collar what you used, I see a black material, home is resin? Thank you for your kind reply.

[Artyom]

Hi dbanner, I wanted to ask you to lock the collar what you used, I see a black material, home is resin? Thank you for your kind reply.

[godigit1]

[ATTACH]45861[/ATTACH]

While looking for something else I found this.
https://www.amazon.com/dp/B01J1GGOA8...5-a5ee48cc718d

[dbanner]

That 1kv ceramic in the photo of the Relic Magnum search head is most curious. I seem to remember seeing a high voltage rated cap on the PCB of Troy shadow or was it a golden mask?
Why 1KV?