cone coil

[golfnut]

Anyone got a view on this type of coil..
A solenoid type with differing diameter ends.

Narrow end at the base..

Whoops wrong pic.

[golfnut]

now with real pic

here

[chemelec]

I make numerous Cone Coils.
This one is about 3" at top, ans 3/8" at bottom.
Height is 2" and Inductance is 104uH.
Good for Bench testing on my PI.

I also make bigger ones, but don't find them all that good for out door use.

[hdphilip]

golfnut,

your first picture pretty interesting too!

philip

[golfnut]

Oh, it was some work I had done for a guy on here for filtering out of band signals away.

I must say metal detectors have a lot of interest for me as they encompass lots of engineering disciplines - it fits with my inquiring outlook.

One thing I think of on a DD coil set is ...

The centre of the Tx coil has the most signal (target illumination.)
The centre of the Rx is most sensitive point .


In a DD the Tx is looking 3" to LHS of target, as is the RX is looking 3" to RHS of target

This must loose a bunch of depth.

One thing to try is to angle the coils slightly to get Tx max and Rx max to converge at say 12" depth - like the lamps on the lanc in the dam busters!



S

[golfnut]

optimum inductor design !! ?

read a good coil design article,

it was saying the optimum coil has a length and a width approx the same

1<length/diameter<4

and keep the turns one wire diameter apart.

One could do this winding a duplicate dummy wire, onto your former and removing it at the end.

Steve