OK well I do. Hi kabier2 The foam coil seems to work well for him but I have made several with no success and I did it to the letter. So here is what I think you should do to have a good coil, at first don't worry about the inductance (we will do that later) turn a coil on a former of the right diameter R= 100 not D = 100 like he has it in his document (It's an error and we forgive him) Use the TX of your detector and a scope to get the coil to run at 14.5Khz (TX coil) then 13.9Khz (RX coil) now here's the trick you need to wind dental floss around your coil till the inductance is 6Mh for TX and 6.5Mh for RX. Once you have done that check your frequency, I'm 99.999% sure that it will be correct and that your inductance will be too. Now you can use some glue to hold it together, you will need some very thin shielding for your coil just remember to leave a gap of about 5mm. On a Coplanar coil you will need to add a bucking coil to the RX coil but I think that you already know what I'm on about the bucking coil being an extension to the TX coil.
Have fun
Xavier
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Xavier