[TowerTalk] DIY Air Wound Coils

[W7TMT - Patrick]

Dave,

Very cool implementation with the 3D printer. I've wound several sets of coils for shorten dipoles supported on pairs of telescoping fiberglass windsock poles. I used the similar, but less sophisticated technique described by AD5X here:

http://www.ad5x.com/images/Articles/CoilRevB.pdf

From my experience with larger diameter coils, you may want to provide notches in the form to allow installing extra temporary support pieces that are used during the winding but then not glued onto the coil. I found that on the 3.5" diameter coils I wound for my 40M dipole that the larger diameter resulted in very noticeable flat spots in the windings between the four main supports. Adding the temporary supports between, and then just not gluing them resulted in a nice round coil.

Flats may not affect the inductance, I don't know. But the rounder units just looked better to my eye.

73,
Patrick, W7TMT

-----Original Message-----
From: TowerTalk <towertalk-bounces at contesting.com> On Behalf Of David Gilbert
Sent: Wednesday, January 18, 2023 19:31
To: towertalk at contesting.com
Subject: Re: [TowerTalk] DIY Air Wound Coils


This should definitely be feasible.  My example was really basic ... 
just a cylindrical hole with a rectangular slot on top of it that only infringes on about 40% of the cylindrical hole.  The remaining 10% provided the "snap".  A better approach to avoid glue would be a tighter fit with a ramped entry.  If the grips were freestanding and not slots that should work well.  Maybe I'll play with it and update the files.

And although I used four bars, I think two might be sufficient based upon the coils I've built with #14 wire.

73,
Dave   AB7E



On 1/18/2023 6:15 PM, Brian Beezley wrote:
> "My final choice was slotted acrylic bars for strength, water and UV 
> resistance, and ease of solvent gluing the wires in place."
>
> Grant, after seeing several neat coil form designs in the style of Air 
> Dux, I've been wondering if a precisely shaped groove might hold the 
> wire reliably without glue. I imagine it snapping into place with a 
> satisfying sound. I suppose this would work well only for a single 
> wire gauge.
>
> Brian

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