Re: Coil forms, Q, and instruments

Jim Sheldon

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 outdoor longevity.

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 - LOL.


------ Original Message ------
From: "davemrtn" <davemrtn@...>
Sent: 7/23/2021 8:17:58 PM
Subject: Re: [4SQRP] Coil forms, Q, and instruments

Jim, what material are you printing with, PETG ???

I wouldn't 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 wrote:
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 HamRadio --

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