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Coil alignment for PI DD coil

A

Anonymous

Guest
Hi,
I have spent a few days going through all the postings to gather all the tips etc that the good people on this Forum are willing to share. Many thanks to all.
The question I have is in relation to the coil placement for a DD coil.Assume that both coils have been wound in a clockwise direction. When placed in the coil former are both coils orientated such that both trace a path through the overlap in the same direction? Or is one coil placed in the oposite orientation.
Can anyone who has constructed a DD PI coil help with my question?
Regards,
Stefan
 
Hi Kev,
I have built several DD coils but really never gave any thought to winding direction, etc as you have mentioned. When I get done, I really can't see the windings and it is easy for me to flip a coil over, so, for me, it could be either polarity.
Now, you do want the polarity to be the same as the xmit, so one could put a dummy resistor across the receive coil and connect a scope to it to see what the signal looks like when brought near a working xmit coil.
What I do is just rough mount the receive coil and test the polarity in circuit. From there, I can easily flip the coil, or simply swap leads. If it is backwards, nothing is hurt, but it simply doesn't work as expected.
If you decide to test the coil in position like I do, make sure to use a non-ferrous object as a test target. Ferrous objects will produce an inverted signal when close to the coil. It is easy to forget this little quirk.
I am sorry I can't give you a more specific answer, but hopefully, the info I provided will help.
Reg
 
Hi Reg,
Thank you for your quick reply to my post. I guess that I will be doing some experimentation to get the setup right for the DD I am building.
Have constructed quite a few mono coils for my Minelab SD2000 and afer a few years of trying "this and that" I have a range of light weight mono coils that I am happy with. The coils are constructed using fibre glass resins and look similar to a steering wheel on a car. I then make a hoop out of PVC conduit and this is clipped onto the outer circumference of the coil. This acts as a skid plate and protects the coil from damage. The coils are much lighter than an equiv Coiltek coil.
Again thanks for your help.
Regards,
Stefan
 
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