HF Antenna Balun

thingiverse

This scad project makes a series of spacers used to hold a length of coax in a cylindrical coil shape to form a choke balun for use with an antenna system. The project as configured makes 4 spacers that produce an 8 turn coil with the turns spaced at 1 coax diameter. I used it to feed a hex beam for 14 through 30Mhz. Openscad source is provided and you can easily reconfigure the project for different coax diameters and different number of turns. Note: each spacer is slightly different as the holes are offset to make a smooth spiral coil. Try not to mix them up! I marked each one as 1,2,3 or 4 before I took them off the printer. If you need to change to different coax, I used a hole diameter about 0.5mm larger than the measured diameter of the coax. The goal is to have a sliding fit for the coax. If the fit is too tight, you will curse trying to thread the coax through the spacers. If its too loose, you will have to use glue to hold the spacers in position.