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I have been building some custom double D coils for my Minelab Explorer and they work fine but I have a couple of curious questions I'm hoping the electronics gurus can answer as I'm just a computer nerd.
First question, I have a large coil that works perfectly but I'm curious, if I pass a target over the outer edge of RX, then the center where RX and TX overlap, and then the outer edge of TX I get a response at all three points...the question is why would my TX coil pick up the target at its outer edge? Its a good 7 inches from the center of the coil and simple thinking would assume since its a transmit coil it should just transmit right? Or is the TX coil picking up the target and somehow passing this signal on to RX? If so I wonder if this can be reduced to some degree or used to some other advantage.
Second question, I'm interested in coil geometry. I have heard that those big foot type coils which are like 5 inches wide by 18 inches long don't have much depth and that a 10 inch round coil will actually go deeper. I have also heard that say a 10 inch eliptical coil does not go as deep as a 10 in round. So it would see that coil width is a factor. Is it because RX and TX are more scrunched together in an eliptical or big foot design, is this inhibiting the magentic field in some way. I'm wondering if a 15 inch wide by 10 inch long coil would go deeper than a 10x10 inch round coil. I suppose this could be a happy medium issue where round gives the optimum depth while wide and narrow coils both loose depth.
First question, I have a large coil that works perfectly but I'm curious, if I pass a target over the outer edge of RX, then the center where RX and TX overlap, and then the outer edge of TX I get a response at all three points...the question is why would my TX coil pick up the target at its outer edge? Its a good 7 inches from the center of the coil and simple thinking would assume since its a transmit coil it should just transmit right? Or is the TX coil picking up the target and somehow passing this signal on to RX? If so I wonder if this can be reduced to some degree or used to some other advantage.
Second question, I'm interested in coil geometry. I have heard that those big foot type coils which are like 5 inches wide by 18 inches long don't have much depth and that a 10 inch round coil will actually go deeper. I have also heard that say a 10 inch eliptical coil does not go as deep as a 10 in round. So it would see that coil width is a factor. Is it because RX and TX are more scrunched together in an eliptical or big foot design, is this inhibiting the magentic field in some way. I'm wondering if a 15 inch wide by 10 inch long coil would go deeper than a 10x10 inch round coil. I suppose this could be a happy medium issue where round gives the optimum depth while wide and narrow coils both loose depth.
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