Coil winding

[johan]

Hey
I'm working on the tesoro bandido II and I calculate my coils.
TX must be n=116
w=2,23cm
R=11,16cm

RX must be n = 162
w = 3,24cm
R = 6,62cm
This is calculated with a wire diameter of 0,2mm
Can sombody tell me how ik can wind them concentric. I tried a lot but the wires are always rolling over. How can i make the coil so that the wires are beside each other.
This would help me a lot forward. Or has somone a other idea?
thx and greets from Belgium

[mike]

Re: Coil winding

It is not as simple as that, you have to cancel the RX field.

I have scanned all the Tesoro coil with a loop on the probe of my oscilloscope.
I have found one big TX coil at the external border of the detector coil. (i can redraw it by finding where the field is cancelling on my loop.

I have found one RX coil at the border of the central hole. I have injected a signal in the coil to trace it.

BUT NO AUXILIARY TX or RX coil !! to cancel the RX field ! (or i am crazy, i don't know)

Then i think the field is canceled with a small ferrite transformer to create a negative feedback in the RX signal.

[Vladimir MInkov]

Re: Coil winding

I think that this idea with the ferrite transformer is only for" how to lost you time".On the search head the necessary balance is accessible by geometry of coils.To put transformer to cancel RX field is not so easy.There will be and phase effects.

[mike]

Re: Coil winding

Yes , but i only want to understand why i don't see any bucking or feedback coil in my comercial tesoro coil !

The reason is purhaps, that i don't see it because the number of the feedback coil is not large enough to be seen by my magnetic field probe !

[Dave Emery]

Re: Coil winding

The feedback or bucking coil is wound around the receive coil and actually uses the receive coil as its form. When you look at the inside of the coil you will see what looks like only two coils. There is an explanation of how coaxial coplanar coils are made on this site. Note that the coil shown is for a PI and not a VLF such as a Bandido. Dave. * * *





Click Here

[mike]

Re: Coil winding

i have made tesoro a coil that works with good performances (at least as good as the comercial one) !

I did not use a secondary TX bucking coil but a secondary RX coil wounded arround the TX coil !

I think it is what tesoro uses and it is why it works so good now !

making a secondary TX coil cancel the field at the middle of the coil. When i spy the field of my real tesoro coil it is not the case !

I will write a precise document to explain how to make a tesoro coil whatever the geometry is (field cancelation issue ,phase and frenquency tuning issue)