Cylinder Coils?

[Nova]

Thanks Carl, you have been very helpful, any idea when your book will be ready? and where can we buy it from?

[Carl-NC]

Okay, thanks Carl., i get ya, so the tests you have done prove this fella Chet wrong?, i am not sure how he came to that conclusion, i just might have to sign up to that forum and ask him.

I have no idea, I'd need to see exactly what he's done.

That table you have shows that a normal " flatwound " coil is one of the worst in the case of far field ,so would be a better coil for shallower targets as proven by most users correct?

If you mean the solenoidal-wound (helical) coil, I don't know anyone who had used one.

When you say "scramble" wound, you mean to say the windings are bundle wound with NO worry about making them fit a desired pattern, so when you wind it where ever the windings end up, they end up correct?

Yes.

PVC wire, could you link me to some please?

PVC-insulated wire is commonly available everywhere. I don't recall where I got this particular wire.

I would be interested in making a DD coil, does your new book thoroughly cover how to make a DD coil as it's on the cover?

Yes.

We know that with a P.I. detector we can hit bucket sized targets at 2 or more metres. So to my mind the TX is not the problem and the specs within reason probably don't matter too much?
Can you explain to me what is the reason that you can't hear let's say a small bullet at 4 feet, if the TX is hitting the bucket at 2 metres is it also hitting the bullet at 4ft?

The EMF induced in a target is proportional to the strength of the B-field and the area of the target. So the bullet has a much smaller EMF, and therefore a much smaller target field. Also, a very large target couples more efficiently with the RX coil. Yes, more RX windings give a stronger target signal, but an equally stronger signal for ground and EMI. You can try it, but generally it doesn't help much.

[Carl-NC]

What is the insulation thickness of the PVC wire and the Teflon wire? Or we could say the outer diameter of the insulated wire?

I'm traveling this weekend, will check when I get back.

[bbsailor]

What is the insulation thickness of the PVC wire and the Teflon wire? Or we could say the outer diameter of the insulated wire?

Single layer coils, either vertical or flat, will have less inductance than a bundle wound coil. The important thing to experiment with is the coil style, inductance, resistance, shape and delay potential for various desired targets.

Here is an example. Beach hunting can be more efficient when using a rectangular coil shape of 6 inches by 18 inches. This allows more ground coverage per sweep but not the most depth. A 15 inch or 18 inch diameter round coil will provide more depth but when sweeping the sand with these large round coils, you need to overlap your sweep pattern.

I have found through experimentation that bundle wound coils using Teflon insulated wire will produce a coil with less capacitance and a lower delay signal due to the lower value of the dielectric constant of Teflon. Bundle wound coils may be more efficient for some targets than single layer coils.

When optimizing a metal detector for a particular target, many things are tradeoffs that should be designed, implemented, documented and measured on a variety of targets in a variety of detecting locations. Try a variety of TX frequencies, preamp gain settings, TX to RX delay and any other variable related to your detector design.

I hope this helps?

Joseph J. Rogowski

[Nova]

Okay, thanks Carl., i get ya, so the tests you have done prove this fella Chet wrong?, i am not sure how he came to that conclusion, i just might have to sign up to that forum and ask him.
That table you have shows that a normal " flatwound " coil is one of the worst in the case of far field ,so would be a better coil for shallower targets as proven by most users correct?
When you say "scramble" wound, you mean to say the windings are bundle wound with NO worry about making them fit a desired pattern, so when you wind it where ever the windings end up, they end up correct?
PVC wire, could you link me to some please?
I would be interested in making a DD coil, does your new book thoroughly cover how to make a DD coil as it's on the cover?
There's one other thing that has been bugging me, so while i have you here could you please answer this for me?

We know that with a P.I. detector we can hit bucket sized targets at 2 or more metres. So to my mind the TX is not the problem and the specs within reason probably don't matter too much?
Can you explain to me what is the reason that you can't hear let's say a small bullet at 4 feet, if the TX is hitting the bucket at 2 metres is it also hitting the bullet at 4ft?
When you see a drawing of say a mono coil field, those field rings get larger but as they get farther away (in a drawing) there not hitting the middle part , so when a coin for example is pictured deeper down in the drawing in the middle of the coil those field lines are not hitting the coin say at 3ft deep, is this the reason you can't hear that bullet at 4ft, (the field lines just don't hit the target) or something else more related to the RX going on.
I am after depth on larger targets, i have the Detech 15in DD spiral coil, i dug an end of an old timers pick at 27-30inches in flogged ground with my 5000, (nobody else heard this target) i have read that increasing the windings of the RX will increase the power of the receive signal but will increase noise, i am willing to go for that extra noise if i can gain an extra 6-8 depth, is that possible Carl to get an extra 6-8 inches by doing this?
I'll leave it at that thanks!!!

[Tinkerer]

What is the insulation thickness of the PVC wire and the Teflon wire? Or we could say the outer diameter of the insulated wire?

[Carl-NC]

What type/brand of magnetic field strength meter did you use for the measurements?

It's a homemade meter, I call it a Magnetic Field Probe. Detailed info is in ITMD3 (coming soon) but I've already talked about in another thread. I don't remember which one.

Carl. i just did a quick google search on 'Solenoidal' coils, no, that doesn't look like it at all. Maybe the style i'm talking about is this type of coil, but i don't know a lot about them so couldn't say for sure!!

#2 in the previous PDF is what I'm talking about. By "solenoidal" I mean a single-layer coil.

[Nova]

Carl. i just did a quick google search on 'Solenoidal' coils, no, that doesn't look like it at all. Maybe the style i'm talking about is this type of coil, but i don't know a lot about them so couldn't say for sure!!

[Nova]

Detectorist, number- 2 is what i'm talking about but layed horizontally, easiest way i could explain it is, let's say you have a straight sided bucket not the slight cone shapes that most buckets are, but to do a flat style winding around the bucket to the desired specs and how many windings that would require, all i'm talking about is a flatwound that is not on a horizontal plane but a vertical one, this fella Chet says that this the deepest coil out of all designs but said there are problems with shielding, i guess i could of signed up to that forum and asked him directly, but this forum has a great many experienced people on it, so collectively will have greater knowledge!!!

[PICON]

Thanks, Carl.

What type/brand of magnetic field strength meter did you use for the measurements?