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Is there more to sensitivity than LCR? I built a 21 inch coil and an 18 inch coil and both have the same problem. I'm getting a very low conductive signal way over on the ferrous side of my ID screen. I have two wild guesses at what the problem is, not enough shielding or my coil is too sensitive and the machine can't balance away the ground.
I used nickel shielding paint on the 21 inch coil, it was quite conductive, I easily obtained continuity with the probes 21 inches apart.
I used carbon shielding paint on the 18 inch coil and laid it on thick, yet I could not get continuity even with the probes only 1/2 inch apart.
I had thought the nickel shielding was causing this low ferrous signal i.e. too conductive but since I have the same problem with the coil using carbon shielding it can't be that the shielding is too conductive. I know this because with no shielding the RX square wave is distorted due to EMI on both coils on the scope. The nickel shielding cleared this right up giving me a nice sharp square wave on RX just like my factory coils. But RX is still distorted on the coil using the carbon paint and I laid it on quite thick so since the factory coil RX is undistorted then the carbon shielded coil which is still distorted is not shielded well enough and so the problem is not that the shielding is too conductive since this coil has the same low ferrous signal problem.
It could be that its not conductive enough...on the coil that I used the nickel paint it actually quiets down and gives me a threshold if sitting still, I don't get the low ferrous signal until I move it. On the 18 inch coil with the carbon shielding I get the low ferrous signal even when its sitting still on the ground.
Okay so maybe my shielding is not conductive enough, maybe but thats not my first choice. Lets say instead that my coils are too sensitive, if so I'm missing something important because my 18 inch coil is wound to yield factory specs inductance, capacitance, and resistance, they are right on. But my coils have a much higher Q and I'm probably using a heavier guage wire on the RX coils than the factory coils. Maybe I need to wind them sloppy or use a finer guage on the RX? Is there more to sensitivity than LCR?
By the way I have a factory 15 inch coil which runs fine at higher sens settings at the same test site and its not the machine since I changed coils and hunted for a couple hours with no issues.
Any thoughts would be appreciated.
I used nickel shielding paint on the 21 inch coil, it was quite conductive, I easily obtained continuity with the probes 21 inches apart.
I used carbon shielding paint on the 18 inch coil and laid it on thick, yet I could not get continuity even with the probes only 1/2 inch apart.
I had thought the nickel shielding was causing this low ferrous signal i.e. too conductive but since I have the same problem with the coil using carbon shielding it can't be that the shielding is too conductive. I know this because with no shielding the RX square wave is distorted due to EMI on both coils on the scope. The nickel shielding cleared this right up giving me a nice sharp square wave on RX just like my factory coils. But RX is still distorted on the coil using the carbon paint and I laid it on quite thick so since the factory coil RX is undistorted then the carbon shielded coil which is still distorted is not shielded well enough and so the problem is not that the shielding is too conductive since this coil has the same low ferrous signal problem.
It could be that its not conductive enough...on the coil that I used the nickel paint it actually quiets down and gives me a threshold if sitting still, I don't get the low ferrous signal until I move it. On the 18 inch coil with the carbon shielding I get the low ferrous signal even when its sitting still on the ground.
Okay so maybe my shielding is not conductive enough, maybe but thats not my first choice. Lets say instead that my coils are too sensitive, if so I'm missing something important because my 18 inch coil is wound to yield factory specs inductance, capacitance, and resistance, they are right on. But my coils have a much higher Q and I'm probably using a heavier guage wire on the RX coils than the factory coils. Maybe I need to wind them sloppy or use a finer guage on the RX? Is there more to sensitivity than LCR?
By the way I have a factory 15 inch coil which runs fine at higher sens settings at the same test site and its not the machine since I changed coils and hunted for a couple hours with no issues.
Any thoughts would be appreciated.
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