Cylinder Coils?

[Nova]

G'day everyone, i'm just after some knowledge regarding Cylinder coils, on a detecting forum there was a fellow i believe he goes by the name "Chet" and he has experimented a little with building his own coils, he mentioned that the Cylinder style coil has the greatest depth out of any design, (that is i believe a vertical flatwound coil which will make the housing much thicker), if it's true that this design is deeper why don't we see these coils anywhere?, there must be tradeoff's i assume with the design explaining why they aren't common?
Carl should know alot about these coils (or maybe not?) if anyone has built one feel free to chime in, if these coils are deeper (by how much extra depth could one expect?)
A mono would be easier to build, but a DD would be interesting, i would imagine the TX would be horizontal flatwound then the RX vertically wound, in my experience with my 5000 i have by much testing can get my 5 to run within an inch or two in depth as my 2200d in it's deepest setting, i like the DD design simply by how quite you can get them to run, so a DD like this could be an interesting build( not that i could do it (yet)).
So what say you?

[Detectorist#1]

What you mean by "cylinder coil" - single row long coil?

[Nova]

G'day Detectorist#1, i am not 100% certain, he or someone else did show a picture of a small coil (this coil looked like a typical mono but was double the height) so i am assuming the winding is flat wound but on a vertical plane instead of horizontally, can you picture that?

[Detectorist#1]

Attached is picture with 3 variants of a mono coil. Double height haves only cylindrical coil in comparison with standard mono. For which option you thing?

[Detectorist#1]

Flat coil in vertical position will have more more height in comparison with standard mono coil

[Carl-NC]

Here are my results, measured from coils I built:



All coils are d_eff = 10" (25cm) and 40 turns which gives ~1mH for a scramble-wound coil. B₀ is the field strength at the center of the coil, B₁₀ is the field strength 10" away. The solenoidal coil (what I assume you are asking about) has the 2nd worst field strength performance, but the lowest parasitic capacitance. This only looks at the TX side but the RX side will be similar. I was actually a bit surprised by how poorly the solenoidal coil performed, I assumed it would be about as good and possibly better than a scramble-wound coil. But apparently the physical height of the coil reduces the effectiveness of the "highest" windings. I think I ran this in FEMM and saw the same thing.

[Altra]

Nice chart Carl. How did you measure R(100kHz)?

[Carl-NC]

I have a DER-EE DE-5000 LCR meter which can measure at 100Hz, 1k, 10k, and 100k. The 100kHz really shows the skin effect.

[Detectorist#1]

Hi Carl,
My experiments also points that scramble bonded magnet wire haves more good result (as distance) in comparison with solenoidal winding type

[Altra]

Thanks, you can see the SRF increases with the lower R 100kHz

[PICON]

Hi Carl,

In your coil results, what size magnet wire did you use and what DC current level was used for the field strength measurements?

[Carl-NC]

All wire is 24AWG. I used an AC drive of 100mA pp @ 10kHz.

[PICON]

Thanks, Carl.

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

[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!!!

[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!!