Sunlu PLA spool cap - for dipole antenna
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You can seal the sides of a 250g Sunlu spool against the weather using some hot glue. Great for wire antennas.
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Model information
- Source
- Printables
- Category
- Mechanical Parts
- License
- Open Community License v1
I do ham radio. An HF wire dipole or EFHW antenna needs to be wound up onto a spool of some sort when not in use.
I do 3d printing. I have lots of spools lying around. Perfect for winding up antennas! The exact spool is: https://www.amazon.com/dp/B0C9933PWG
The middle of a dipole needs a feedpoint, usually with a balanced-to-unbalanced transformer (balun), to balance the signal and choke the common-mode current. It's nice if this part doesn't get rained on.
So I printed this cap. It snaps in place for easy prototyping. It has some attachment points for small zip ties on the inside, which can hold antenna wires and a ferrite toroid. Obviously, you'll need one cap for each side to seal it up. You need to drill/poke some small holes in the spool center for the wires and feedline to pass through.
When you've got everything just right, you can seal it with hot glue. Hot glue melts 10 degrees before the Curie temperature of the toroid, so that does double duty as a failure indicator.
I'm looking forward to testing how it performs if I wind up half of a 40m dipole, and try to use it as a 20m antenna. I figure the spool should just act as a coil form, resulting in some slight inductive loading... but it could resonate without a tuner. Similar to "spooltenna".