I want to modify my existing concentric coil and make it eliptical. Can I?

[Mike Hillis]

Hi guys,

I have a Bounty Hunter Tracker IV that I enjoy using, but it has a slow reponse time so is not very good in areas where the targets are close together. Since BH doesn't offer a DD coil for their machines, I was wanting to turn their concentric coil into an eliptical. The idea I have currently is to remove the cover, remove the coils and reform them using some plastic tubing.

So I have a couple of questions.

1. Can I do this?
2. Would I get better results if I left the transmit loop round and just squeezed the receive coil eliptical, or
3. Would I get better results if I squeezed both the transmit & receive coils eliptical?

Thanks for the help.

Mike

[Reg]

Hi Mike,

I doubt that modifying the coil will help any slow response you have. Normally, a slow response is a function of circuit design including the motion filter time constants.

As for modifying your existing coil, I haven't looked inside a BH coil, but many are epoxied making them difficult to impossible to form to a different shape.

Even if this is not the case, modifying the shape could upset the null making the coil useless.

I would recommend you try to build a different coil from scratch. You would need to know the inductance of the transmit and the receive coils. Then you could use the basic technique posted by Dave Emery about building a concentric coil.

You might even try to build a DD coil also. There are a lot of coil housing available now, so you have a wide range of sizes you could try.

Reg

[Mike Hillis]

Thank you Reg for your response.

I would rather build a DD coil for it, as these are my favorite coils.

How would I go about learning what the inductance of the coils are?

Thanks,

Mike

[Reg]

HI Mike,

I was hoping someone had already measured the inductance of the coils and would post something.

You will need to measure the coil that is on your machine to see just what the inductance of that coil is. Measure both the xmit and the receive with an inductance meter if you have one.

Now, when making a DD coil, try to match the inductance if possible. Also, I would recommend you use the same size wire or larger for the xmit. You can use very small wire for the receive.