On Aug 16, 2022, at 22:43, David McGaw <david.g.mcgaw@...> wrote:

? Indeed.? Like many things, true in the limit.? A toroid with just a few turns does have significant stray fields, but better than a solenoid coil.

D

On 8/16/22 7:39 PM, Ashhar Farhan via groups.io wrote:

David,

I did a bit of experimental work on this. The toroids need more than 15 turns or so for the self-shielding to work well.

At fewer turns, the shielding though better than that of a conventional inductor, wasn't good enough to be used in a bandpass filter. In the Daylight radio, I had to add shielding between the three sections.

- f

On Tue, Aug 16, 2022, 11:48 PM David McGaw <david.g.mcgaw@...> wrote:

Yes, understood.? Just thought I would let it be known that it is not the core that shields a toroid.? It is inherent in its shape.? Physics.? :-)

On 8/16/22 9:49 AM, Ashhar Farhan via wrote:

David,

Shielding is not the issue. Losses are. Lower Q leads to higher losses. The Q is determined by the material inside the toroid. Air/Vacuum is the best material with least losses for an inductor, whether a solenoid or a toroid.

On Tue, Aug 16, 2022, 6:23 PM David McGaw <david.g.mcgaw@...> wrote:

Toriodal inductors are inherently shielded by their geometry, no matter what the core material is, air, ferrite or other.

73,

David N1HAC

On 8/15/22 8:24 PM, Ashhar Farhan via wrote:

David,

The inside of the toroid should be hollow and it not hollow it should have as little in-fill as possible. This is the key to high performance 3D printed toroids. PLA or ABS are lossy and they can lead to lossy filters.

- f

On Tue, Aug 16, 2022, 4:16 AM Siegfried Jackstien <siegfried.jackstien@...> wrote:

would not a simple tubing do the same?? .. the "shielding" of a coil wound on a ferrite core comes from the core material ... so i guess a normal pastic tubing will work equally well if not better (fewer loss cause fewer plastic inside the coil)

so ... what is the reason to print plastic toroids??

dg9bfc sigi

Am 15.08.2022 um 23:50 schrieb David R. Hassall WA5DJJ:

Dear group,

I asked a friend of mine to build a master toroid stl file that we can put in our 3D printer software and come up with the plastic toroids almost any size we want.?? The Master was built on the basic size of 1 inch in diameter with a height of 1/2 inch and a thickness of? 0.2 inches.?? I use the CURA program to build my 3D printer files and it will allow me to scale all three axes once the basic 25mm toroid.stl file is loaded into the software.? It also allows you to print almost any number of a basic design in one printing.?? Here are some examples that I printed this morning:

I just used the scaling values of 25%, 50%, 75% and 100% to get the different sized plastic toroids pictured above.? So with the master stl file anyone with a 3D printer should be able to print almost any size plastic toroid form that you would need.?? I have attached the master stl file to this Message and it should enable anyone with a 3D printer to make the plastic Toroids that they need for the Daylight Radio Project.

Take care and have fun.

73 Dave WA5DJJ
SUPER QRSS GRABBER