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I have a Discovery 3300 with a stock 8" coil. The detection depth on a dime with the sensitivity cranked up is only about 5 or 6 inches, and it's killin' me. I needs me some silver, and it's a bit deeper( I suspect) than what I'm getting. I'm looking for a schematic or wiring diagram for the coil on my 3300 so I can wind my own concentric 10 or 11 inch coil. I checked on an inductance meter, and 1 coil reads 3mH, and the other 0.22uH. If those are good numbers, I can match them. But since this is a VLF, I'm not sure if the coils are shielded, and it has a push-in 5 pin connector, and I'm not sure of the pinout. If anybody out there knows anything about the Discovery 3300 coil setup, it would be awesome.
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It's not the coil that's restricting the depth, it's the control-box electronics, really. You could try the 10 inch BH coil, you might gain an inch of depth with it. -
But that inch could have something other than pull tabs and zinc pennies
I could buy one, but I can't afford it right now. I do have all the stuff I need to wind my own, though, from radio projects.
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OK, so it appears my machine is a piece of junk, but I still think it would be good practice to roll my own coil. If nobody knows about concentric coils for this thing, what about a DD coil? Can a DD coil work on the discovery 3300? If it don't give me much depth, at least it would cover more area each sweep, right now I have to swing this thing very slow to give it time to read at full depth.Comment
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I see the Fisher F2 and F4 coils with a plug-in socket are interchangeable with the BH3300. Does anyone have anything on the 11" DD fisher f4 coil?Comment
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OK, I have an idea. What if I wind a DD coil of, say, 400uH each coil, then put a small variable cap(trimmer) across each coil to tune it. Would this work with the detector, or would it not work properly? Has anyone out there ever tried this with any detector before? I'm just thinking that the "apparent" inductance of the coils would match the detector, like impedance matching circuits together......Comment
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It could work, but question is how. BHD 3300 consist not only out of TX and RX stage there are filtering and phase sensing circuit inside too.Originally posted by CladKing View Post
400uH pro coil is not good match in your case especially not for RX coil.
Your idea from previous post to adapt F4 DD coil to BHD3300 sounds better.
If you wish to start with your own DD coil design then you need to try instead of 400uH pro coil: say 2,400uH for TX coil and 4,400uH for RX coil ( in mH: 2.4mH for TX coil and 4.4mH for RX coil).Comment
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I didn't suggest the F4's 11 x 7 DD coil to you originally because, although it will fit, it is unlikely to give noticeably more depth than the 8 inch concentric coil. Since you wanted depth, I recommended the 10 inch concentric. If you are serious about home-building a coil, please do it properly, don't improvise. By the way, variable capacitors only go up to 500pF typically, not tens or hundreds of nF.Comment
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Thank You WM6, that's the most information I've heard in several days that I may be able to use to at least try. I'm guessing the inductance measurements I got off the stock coil are way off because of other components imbedded in the coils. I have some wire to burn, so a shot that may work out is better than no shot at all. Thank you all, whether it works or not, I will post updates and pics. If I botch it, at least other people can save some time and money.Comment
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Here's the info you need for coil-building:http://www.geotech1.com/forums/showt...her-F2-F4-coilComment
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Thank you!!! This helps tremendously.Comment
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