a more detailed can this be done (improving coil design)

[strike it rich]

hi after posting can this be done it seems I confused a couple of people with what I was trying to get across my fault bad explanation so here go's.

As i see it modern Md's work using radio waves they go up down left and right. What I was trying to ask is if the top of the coil was covered with a material that reflected the waves back down and inside the coil was the same material spinning thus the radio waves could only go down added to this they get channelled into a small concise area would this have the effect of increasing the strenght of the waves thus increasing depth.

I know metal detectors have come a long way and that coils have too what iam proprosing is a totally new radical design for a coil your thoughts please

of course iam willing to build a one some day but before i waste my time and money i would like to bounce the general idea off you guys and gals.

[Rob in KS]

What you are talking about is a reflector. Think of the coil as an antenna. You want to focus the energy from the coil in one direction. Thats what directional antennas are all about. Look up a corner reflector antenna or a parabolic dish. The main problem will be the frequencies your talking about. I think most detectors run in the kilohertz range. That makes the wavelength HUGE. The reflector would have to be a certain fraction of a wavelength from the coil so that the waves from the coil and the reflector reinforce each other.

You can learn more by reading up on antenna theory.
The Radio Amateurs Handbook would be a good start.

[gallileo60]

I stated alot of this on the other post....It does seem as tho you might be able to reflect some of the energy downward..Im not sure how you would do this..I have built several directional antennas (Bought a few too) Beams, Yaggis, quads, Just dont know how you would do this without size being a factor..Im sure some of the high dollar (read 30,000, or so) detectors do something along this line...I bet there are some smart guys out there that have some ideas...Then again I dont know how much like an antenna the coils are, we know they are very small for the frequincy they operate on, so they must be a fraction of the wave length...