[ivconic]

Originally Posted by Esteban

Thanks. I use the principle of White's... you know what for! So, I "invent" my own system...

Actually; i always wanted to read detailed technical explanation about TM808 design. Not manual, not review - but details about electronic stages, roles of each stage and idea of design itself.
I can not say that i don't know how 2 box supposed to work, i know some details of course. But i would like to see and read facts from designers. Pitty i never saw anything simillar. I like Payne's articles just because he talks pretty straightforward and it is easy to learn from him. I can say that also i liked Carl's articles on HH subject; also straightforward and understandable. Andy Flind also, Don Lancaster also. But majority of others are writing pretty general, hard to learn details.
So speaking of TM808...Esteban..you would be mostly on your own, when designing such coils..

I can point you on "Deep seeking metal locator" by Phil Wait and Roger Harrison, i beleive you already saw that project. There you can see pretty good explained coil & loop coupling, for such matters that you are planing to explore...