Would this work?

[Rollin_sb]

Would either of these two designs work to increase coverage area and/or depth while retaining shallow detection quality?

[Funfinder]

Not bad, asking such questions which I'm also interested since a longer time already! I don't think you are just a Junior Member.

After many thoughts the best solution would be "V*gina-Style" hahaha: with a very thin DD-coil slit in the inside (just 3cm broad but 20cm long) made out of very thin wires and using a different frequency so it is almost "invisible" for the surrounding large DD coil which is (both halves) at least 60cm "long" and 50cm broad.

That way it is possible to find very deep stuff but also gold-nuggets at the same time - especially if the detector uses 2 different circuits for the both DD coils!

The sweeping left to right with a thin "slit-coil" will cover a great amount of area for very small stuff while the overall-search-speed still remains pretty fast.

The main issue here only is that the outer coil must not get too much distorted by the inner coil. But this is not so much of a problem if the circuit is stable - you also can put directly nearby the coil a metal-object and it becomes invisible after resetting the signal-level to zero.
This is the same with a pinpointer where also some metal is already pretty close to the coil.

But I would make at least 10cm distance between the two DD-coils and of course a different frequency - for the small stuff a higher frequency (25kHz or something) will be better anyway.

I hope you can follow me - in the inside you will have a ()-shaped DD-coil (but very narrow) while on the outside is the 65cm (28'') large DD-coil.
This way finally the treasure-hunters will get a fantastic 2in1 coil which detects very small stuff (3mm gold-nuggets) but also 2 meter deep stuff at the same time! As long as the search-speed is not too fast, because smaller stuff sometimes needs a little bit more patience.

[Skippy]

The '28 inch' version may stand a chance if you have ONE transmit coil, and two different-sized receive coils.

[Carl-NC]

Would either of these two designs work to increase coverage area and/or depth while retaining shallow detection quality?

You'll need to explain a little more. Is this PI or IB? Are these double dual-field coils or is there a TX coil in there somewhere?

[Funfinder]

Seems that Rollin-sb drank a bit too much fantastic Tennessee Whisky or Moonshine booze, so he can't answer any longer! hahaha

Instead of "Vag*na Style" - also known as VaChina for the pirated coils - hahaha, there also would be a slit-version hahaha possible, which is a bit different in design:

The DD-Coil is in the front "closed" but near the feet it is open and creates a triangular slit where the second and smaller coil fits in!
Undisturbed or better said without "enclosed" fully by the large DD-coil. Or in other words explained: The large DD coil looks a little bit like an arrow peak while the small sits inside the shaft.

Using the small coil as Pulse-Induction without DD also would be a possibility but I have some headaches with this design, because it really must be super fast and PI normally is not super fast.

The "complete" coil will be moved within 1/5 second from left to right and right to left over a 2 meter distance and the little PI must be fast enough for this.

This slit near the feet with hole in the middle would have the advantage of easier pinpointing the loaction of the relative small targets.
But some hole in the middle of the coil has to be standard anyway. PI just might be deeper and better for gold-nuggets at "heavy" soil.
But the slit in the middle can be made longer - up to 25cm - (so it catches more finds) - and is geometrically and energy-balanced better.

And for sure there are needed different frequencies and detection signals plus also different signal outputs at one and the same time and not interlaced. Otherwise you will just distort the other coil or reduce the sensitivity.

Place some rather small coil from a switched on PI detector near or even directly over some larger coil of an IB-MD and test how good it fits together! Especially if you sweep some 1/5'' or 5mm stuff a little bit faster over them.

[dbanner]

Scaling up is always a challenge.

Ground becomes a problem.

I'd say, no more than 18 inches, we could handle in analog.

Beyond that, you're gonna buy Twitter.

Elon musk. Let's do the musky!!!!

Hi Carl.

[dbanner]

With the benefit of hindsight, I sounded rather silly.
I should have explained the physics involved.

[dbanner]

Strong electromagnetic fields are very unstable. Inherently.
Now what we do is to try to take and harness.

[dbanner]

And ultimately, tame.

[Rollin_sb]

I'm sorry its taken me so long. I've been preoccupied with other matters, including my S.PI.Pro parts and build. With this post I kinda got the cart before the horse. I plan on picking this thread back up when I get my project ready for a coil. Thanks Y'all.

[Zincoln Miner]

I'll wait for the clam bake.