Will round DD coil still have a knife edge

[Matt_Rowe]

I was wondering if i use this coil mold in the shape its in, as a DD, will i at least get a 5 inch knife edge since it is a 5inch round coil, or will i just get a DD that works as concentric.

[waltr]

The sensitive area is where the two coils overlap.
With the most sensitive where the overlap is widest.

If that coil shell is 5 inch diameter on the outside then the sensitive width looks to be 1.5 inch

[Matt_Rowe]

Thanks, so that is why DD are elliptical, and so long, so you end up having a long narrow knife edge in the middle where the space is the same, i will pass then, but it would make a nice shooter DD small round coil maybe.

[6666]

Thanks, so that is why DD are elliptical, and so long, so you end up having a long narrow knife edge in the middle where the space is the same, i will pass then, but it would make a nice shooter DD small round coil maybe.

Like this

[Matt_Rowe]

yes, if you notice in your pic that the DD round has a lot of equal space in the middle, the pic i posted does not because the plastic divider cant be changed, so there's only a small window or space in the middle, it might make a decent DD coil in a mono shape though,but would act as a concentric, but would pinpoint well. but when using DD on my vlf i get a knife edge to cover more ground, so don't have to overlap so close, that's why i was asking, but the pic i showed, i cant make the space in between the coils, the same distance from edge to edge as in your pic.

[Qiaozhi]

I was wondering if i use this coil mold in the shape its in, as a DD, will i at least get a 5 inch knife edge since it is a 5inch round coil, or will i just get a DD that works as concentric.

[ATTACH]53077[/ATTACH]

That looks like a Butterfly coil. You won't get a "knife edge" from top to bottom as the sensitive area will be under the overlap.

[green]

I charted signal vs distance for a DD coil awhile back. "knife edge" for close distance targets, similar shape to a round mono at distances greater than 1/4 the diameter. Looked at my chart, wasn't as clean as I would like. Wondering if DD is "knife edge" at longer distances or just close.

[Matt_Rowe]

I was thinking the over lap wouldn't work as i wanted to,
All i have right now is a vlf tesoro lobo with the 6x10 wide scan, although the coil itself might be a 5x9 because of thickness of shell.
when i detect i can get a single from tip to toe and along the whole middle, great for covering ground, but not so good on pinpointing.
when i pin point i go over target, get in middle, then pull back until sound goes away, then forward until tip gets signal, then i dig under tip of coil.
i am building my first PI, and am looking into different coils for it, i bought the surf pro from a member here. just the finished board with the pots, ect.
i ordered a beach E from Andy. to build,
Green, not sure, since i only have had elliptical coils, i had a concentric on a Garret green box, it pinpointed excellent, and discrim was great also, depth was great also, easy to pinpoint, but had to overlap very close, took a long time to cover ground

[Matt_Rowe]

I decided not to buy it, just got my first pi board, built from a member here, and have a beach coming from Andy.
Just dont want to buy a bunch of stuff and waste money sand time

[Matt_Rowe]

That looks like a Butterfly coil. You won't get a "knife edge" from top to bottom as the sensitive area will be under the overlap.

I decided not to buy it, just got my first pi board, built from a member here, and have a beach coming from Andy.
Just dont want to buy a bunch of stuff and waste money sand timeThat looks like a Butterfly coil.

[Tinkerer]

I charted signal vs distance for a DD coil awhile back. "knife edge" for close distance targets, similar shape to a round mono at distances greater than 1/4 the diameter. Looked at my chart, wasn't as clean as I would like. Wondering if DD is "knife edge" at longer distances or just close.

This is similar to the results I obtained. At closer then 1/4 diameter, the sensitivity in increased. further out, the sensitivity /depth, is decreased. An advantage is the blade-like detection area of nearly the diameter of the coil.

[green]

Like this

https://www.geotech1.com/forums/atta...6&d=1598413327 Can someone explain what the pictures are showing. Appears they select a target just detectable at near coil diameter and show detection distance or amplitude when target is not over center of coil?

[Nandor]

It is the shape of the magnetic field of the Tx coil.

[green]

It is the shape of the magnetic field of the Tx coil.

ITMD draws magnetic field of the Tx coil different(page 44).

[Nandor]

It's just for educative purpose.