I was building multiband end fed antenna for 40-20-10m as per instructions on the Nonstop Systems web page Multiband End Fed by Frank N4SPP. I needed to build the loading coil, but the problem was that all materials were too heavy, they were putting excentric load on the fibre glass rod and I did not like the way how the antenna wire was connecting to the coil. So I have created a 3D model for printing that has following benefits:
Coil inductance: 34uH
Wire between 64:1 balun and the coil: 10.1m
Wire between coil and antenna tip: 1.85m
The Wago clamps are holding in place only by presure of the 3D printed material, there is a little notch helping this. This is the method even the original Wago clamp holders are using. The screws do not tap to the plastic material, but there is a nut inside of the coil former. It has to be held in place by small pliers before the thread taps.
I wanted to have coverage of 30m and 17m with the same concept of an antenna. I have just simply tried in the backyard empirically and it turned out that with the same coil, the two bads can be covered!
Coil inductance: 34uH (same coil as above)
Wire between 64:1 balun and the coil: 7.48m
Wire between coil and antenna tip: 0.83m