I'm using PLA2 or PLA+ both which are much easier to print
with than PETG or ABS and are virtually NON-Toxic (ABS sure
isn't). I have found that the PLA2 and PLA+ both last quite
well outdoors, even in sunlight as I have a bunch of garden
characters that have been out in the sun, rain, snow and all
sorts of other weather for over 2 years with very little
degradation, mainly only a slight fading of the colors.
These antenna coil forms and insulators are designed for
temporary portable antenna use and not really intended for
permanent outdoor installs anyway, but I do intend to put one up
in a semi-permanent install here at the house, just to test
I used FilaCube "Mint Blue" PLA2 for the ones in the
pictures. The tolerances on the coil inserts are pretty tight
so not sure how PETG or ABS would print - each persons printers
tend to print a bit different depending on machine tolerances
and personal print profiles. I won't publish my print profiles
as I'm using Creality CR10V2 printers and most people out there
are using something else. There are two versions of the coil
form, one with no "No Twist" inserts and one without that will
be in the STL file when I get it ready for posting later today
as well. The one without the inserts is for use in "Tank"
coils, etc. It was an original experiment just to give more
defined grooves for the coil than the one that Jim G. came up
with using TinkerCad and through a sheer stroke of luck, wound
with 16 turns of #20 it came out almost dead on the 4.7uH
necessary for a 20 meter trap coil - I did not plan it that way
------ Original Message ------
Sent: 7/23/2021 8:17:58 PM
Subject: Re: [4SQRP] Coil forms, Q, and instruments
material are you printing with, PETG ???
use PLA, but ABS would last longer than PLA, but I think
PETG might last the longest ??
David Martin - NA1MH
- Mountain Home, Ar.
Wherever I go, there He is.
On 7/23/2021 8:01 PM, Jim Sheldon
Jim G's work inspired me to work on a 40/20 meter trap
doublet/dipole/inverted vee with 3D printed trap coil forms
and insulators. I have the traps coil forms done and the
end/trap center insulators done and I really got lucky. A 20
meter trap should have 4.7 uH worth of inductance with a 27pF
capacitor to resonate at 14.100 MHz and TOTALLY by accident,
my initial print of the coil form wound with 16 turns of #20
wire just so happened to come out to just a bit over 4.7uH
when I measured it.
I worked on the design (I used AudoDesk's (free for
personal/non-commercial use) Fusion 360 as my CAD program.
F360 gives a bit more finesse when making threaded cylinders
than TinkerCad does.
Taking Jim's advice, I also added blockers to the inside of
the coil form so the insulator will slide tightly inside and
allow you to wind the coil first and pick which 90 degree
point gives you the best coil positioning.
Here's a couple of pictures of the lot.
Jim Sheldon, W0EB -- 3D printing is a super 2nd hobby to