Work in progress!!!

When soldering the segments of a collinear antenna, care must be taken not to shorten a segment's inner conductor to its braided screen at segment joints. This spacer keeps the inner connector isolated from the braided screen at joints. Further, it gives the joint some rigidity avoiding fatigue.

You may have to customize the dimensions of your coax cable into your specific .stl file

• by means of the Customizer (link above, below picture) or
• by editing the dimensional parameters at the top of the OpenSCAD source file (see below).

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Update 1 October 2024:

I added .stl files for a number of common 50 Ohm coax cables with outer diameters suitabel for collinear antennas.

Update 30 September 2024:

New design: Use two spacers back-to-back per antenna segment joint. You may fix the two spacers by glueing before soldering or wrap in sticker tape after soldering.

Measures to be customized:
d_cable: Outer diameter of the cable including bent-back shield
d_insulator: Outer diameter of the inner insulator
z_bottom: Thickness of the bottom. Two 3D printed layers (e.g. 2 x 0.3 mm) should be sufficient. The bottom separates the two antenna segements and should be included in the segement length calculation, at least at very high frequencies. When using a back-to-back pair of spacers between antenna segements, then the additional spacing between two antenna segments is twice this measure (e.g. 4 x 0.3 mm).

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As always I include the OpenSCAD source file for you to adapt and/or improve:

• Download and install OpenSCAD from https://www.openscad.org
• Launch OpenSCAD and open the enclosed OpenSCAD source file (/File/Open).
• Amend the parameters at the top of the file or even amend the code.
• Save your changes (/File/Save).
• Render the design (/Design/Render).
• Export the rendered design e.g. as a .stl file (/File/Export/Export as STL).
• Slice and print.

See my other designs at
https://www.thingiverse.com/thinger13/designs