[WM6]

Originally Posted by ivconic

. For example; i would like to know how they calculated coupling relation between Al loop and small coil inside it? What relation? What is resonance of Al loop? What happening if loop was with different sizes? What are merrits and what drawbacks from such coupling. Is loop size dependable on working frequency and how? How possibly that loop can be suitable for such low frequency? Is it the coupled coil the one which solving that issue?

What do you mean by "Al loop and small coil inside it"? Maybe schematic is some unclear regarding coils, but Al loop are not inductive coupled to "small coil" but electric connected by wire in one only coil. "Small coil" are secondary winding inside ferite potcore and form togheter with Al loop one coil which resonate down harmonic to primary (tunable) LC tank. So loop and "small coil" byself resonate out of TR frequency and are by this only slightly coupled which cause by near target escape from balanced (tuned) nulling at given resonance and by this tone in RX (like by un-nulled device).