Crazy idea..

[bklein]

Could you take a small coil and make a secondary coil (ideally Bigfoot type) that would snap on to it? Kind of an air core transformer concept...

[Skippy]

A picture is worth a thousand words.

[kt315]

all VLF coils are an air core transformer. in what question?

[bklein]

Stock detector has small mono coil #1.
Coil #1 is pressed against a similar coil#2.
Wires from coil#2 tied to a coil #3.
Will coil #3 be able to detect a target and have the detector sense it?