Directional coils?

[Redfoot]

Coils are presently omni directional just move your spade above your coil and it will register, it there any way of making coils directional so all the emf is directed into the ground thus improving depth penetration in to the ground? any one its my first post on here

[homefire]

Garret had a sharp shooter coil Coaxial with the coils stacked and wound on the vertical plain.

Looked like a BIG hockey Puck.

Very little sensitivity to the sides but vary good on the up and down.

[John in NC]

An interesting thought. I too would like a directional coil, but the problem is anything that will block the sides or top will cause the coil to overload. Without a block you have to start thinking about reflecting. It's not there yet because we haven't tried the right thing. I'm still hopeful.
John

[golfnut]

If you could reflect energy from above coil - downwards and phse it so it adds to the normal downward signal.

Ur trying to make a tv aerial like a yagi affair.


Id like to use a bar magnet spinning with a motor to pump field into the gound.

It would be massively more poweful than a small signal oscillator.

Steve

[WM6]

You need 3 loops coil and bigger distance between loops to get better results. Stacked in tower. A little unpractical coil.

[Carl-NC]

Coils are presently omni directional just move your spade above your coil and it will register, it there any way of making coils directional so all the emf is directed into the ground thus improving depth penetration in to the ground? any one its my first post on here

I think you mean "bi-directional" instead of omni-directional. Most coils have equal sensitivity above & below the plane, but not much sensitivity to the side. Coaxial (stacked) coils have even better sideways nulling.

I have never seen a uni-directional coil. The avatar used by "Tinkerer" show a magnetic field for a possible design, but not sure if anyone has ever built & tested it.

- Carl

[simonbaker]

If you could reflect energy from above coil - downwards and phse it so it adds to the normal downward signal.

Ur trying to make a tv aerial like a yagi affair.


Id like to use a bar magnet spinning with a motor to pump field into the gound.

It would be massively more poweful than a small signal oscillator.

Steve

I've always wanted a mag field that you could "focus", but it seems we're limited because we're not working with radiative field, i.e., our wavelength is way too long to do any fancy phase stuff.

I've wondered about a reflector, but that probably is just a massive target that might overshadow other targets -- or maybe not? And again, frequency maybe too low for effective reflector physics??? I've thought about magnetic shield material, way beyond my understanding at this point though.

It's fun to try to squeeze extra performance out using some novel ideas, but it is amazing how quickly you depart from the sweet spot of performance/simplicity ratio.

I've wondered about a moving magnet too -- hope you experiment with it.

-SB

[Tepco]

This is interesting, i never built or used stacked coil configuration on any detector. But "omnidirectional" coil is nice idea. Looks like something impossible, like single pole magnet, but such thing actually exists (or at least something close to it) search for "Hallbach array" for example. Basically, multiple magnets oriented in such way, that flux will almost cancel on one side and add up on another, old trick from '60s not much used. If work whit magnets, must work whit coils too...

[Tinkerer]

I think you mean "bi-directional" instead of omni-directional. Most coils have equal sensitivity above & below the plane, but not much sensitivity to the side. Coaxial (stacked) coils have even better sideways nulling.

I have never seen a uni-directional coil. The avatar used by "Tinkerer" show a magnetic field for a possible design, but not sure if anyone has ever built & tested it.

- Carl

I did a number of experiments with bucking coils, inspired with the magnetic field visualization that I use for Avatar. Some of the coils indeed were much less sensitive upwards than downwards.
However, if the intention is to increase the field strength into the ground, it is better to use a coil wound in a simple round coil bundle. The field strength can be increased by a factor of about 18, with a resonant or quasi resonant TX that recycles 90% of the power.
The price is a thicker wire and heavier coil.

Tinkerer

[Geo]

I did a number of experiments with bucking coils, inspired with the magnetic field visualization that I use for Avatar. Some of the coils indeed were much less sensitive upwards than downwards.
However, if the intention is to increase the field strength into the ground, it is better to use a coil wound in a simple round coil bundle. The field strength can be increased by a factor of about 18, with a resonant or quasi resonant TX that recycles 90% of the power.
The price is a thicker wire and heavier coil.

Tinkerer

Hi Tinkener.
Sorry for my bad English but i don't understand very good. Can you explain more simple (for me) by round coil bundle??

Thank you

Regards

[Tinkerer]

Hi Tinkener.
Sorry for my bad English but i don't understand very good. Can you explain more simple (for me) by round coil bundle??

Thank you

Regards

Hi Geo,

attached is a picture of a "bundle wound coil". It is the simplest way of winding a coil.

For the 18 times increase of TX power that I mention above, look at: http://www.geotech1.com/forums/showp...&postcount=819

where Aziz describes in detail how the TX method works.

Tinkerer

[Geo]

Thank you Tinkerer