TGSL coil Help

[Tibuck19]

A question for all you VLF coil makers out there, this is more of a math question, When I make a DD coil how do I determine the coil diameters , of course a DD has two coils and say I want a 12 inch DD, normally with a mono loop id use the Inductance calculate and input the wire size with diameter of coil and presto I know how many loops it needs, however the DD is not a perfect circle, So how do I determine its diameter ???

[kt315]

put a wire/thread on D uncircle so end will closed to start, one loop. pull it off and measure its length.
now you know circumference/perimeter - P. then calculate the diameter D=P/3.14.
now using the diameter you can calculate the inductance.

[kt315]

or, by that (sorry i do not know word in english of the instrument)

https://www.youtube.com/watch?v=5sdztFWcBsE

[Tibuck19]

put a wire/thread on D uncircle so end will closed to start, one loop. pull it off and measure its length.
now you know circumference/perimeter - P. then calculate the diameter D=P/3.14.
now using the diameter you can calculate the inductance.

Simple yet efficient, Now why didn't I think of that. lol Thanks KT I feel like a blond girl that just slipped on a banana peel.

[dbanner]

This is nonsense, a circle whose circumference is equivalent to the perimeter of "D" will not have the same inductance. The shape characteristics/geometry of the coil influences it's inductance. There is no such thing as a"diameter" of D shape. There is only the diameter of a circle whose circumference is equivalent to the perimeter of the"d".
There is no coil calculator/ formula for the D. There is only crude approximation. This was discussed elsewhere on forum.
A formula can be derived by wrapping one turn at a time of specific size wire, at each turn, measuring the inductance, then plotting the data. But who wants to do that?
Some relationship can be established between the area contained within the d and the area of a circle with equivalent circumference, but it is only ballpark estimate which can get you near to where you want to be.
Furthermore, I suspect that different sizes of "d" will have disproportionate inductances because it is only symmetrical across one line of symmetry, whereas a circle has infinite lines of symmetry. The d shape is somewhat amorphous.

[Gwil]

For what it's worth, my crude approximation is to measure the area enclosed by the D coil, then calculate the radius of a circle with the same area. Put that radius into Qiaozhi's famous inductance calculator. Measured inductance checks out within a few percent. Maybe I've been lucky, but it's worked for me.

(See the thread "calculate inductance DD-Coil and square coil" for a discussion of this subject)

[dbanner]

A few percent could mean adding or removing a good number of turns, but at least it gets you near enough where you can make the adjustments. Never an easy task.
Concentric coplanar arrangement is much easier to calculate accurately, but its construction more difficult.

[kt315]

This is nonsense, a circle whose circumference is equivalent to the perimeter of "D" will not have the same inductance. The shape characteristics/geometry of the coil influences it's inductance. There is no such thing as a"diameter" of D shape. There is only the diameter of a circle whose circumference is equivalent to the perimeter of the"d".
There is no coil calculator/ formula for the D. There is only crude approximation. This was discussed elsewhere on forum.
A formula can be derived by wrapping one turn at a time of specific size wire, at each turn, measuring the inductance, then plotting the data. But who wants to do that?
Some relationship can be established between the area contained within the d and the area of a circle with equivalent circumference, but it is only ballpark estimate which can get you near to where you want to be.
Furthermore, I suspect that different sizes of "d" will have disproportionate inductances because it is only symmetrical across one line of symmetry, whereas a circle has infinite lines of symmetry. The d shape is somewhat amorphous.

my way is an approximation. i do not write its sure way. we are living in the Universe and all around you are just nonsense.
you know that good dear DB.
so you would have to begin from phrase 'we do not have sure formulae for D coil nowhere'. only that is true.

[dbanner]

KT, it is you who should have begun from the phrase "we do not have sure formulae for d coil....", But you didn't, giving the reader the impression that this is good and easy, accurate solution, when in fact it is only crude approximation.
I was only clarifying.
A formula for a standard "D" coil can be easily derived, but nobody seems to be willing to undertake this task.
Once derived, it can be the basis of a D coil calculator.

[Tibuck19]

KT, it is you who should have begun from the phrase "we do not have sure formulae for d coil....", But you didn't, giving the reader the impression that this is good and easy, accurate solution, when in fact it is only crude approximation.
I was only clarifying.
A formula for a standard "D" coil can be easily derived, but nobody seems to be willing to undertake this task.
Once derived, it can be the basis of a D coil calculator.

There is nothing that is not solvable with a mathematical equation, That being said, im not the man for the job hahaha however, I do know a math wiz perhaps I can talk to him about, it and see if he can not figure something out, then its just a mater of making a new little calculator program in Visual basic or in Java...