S-Band Helical Antenna

S-Band helical antenna based on the UHF-Satcom design.

This is a pretty hefty wire holder - one piece because it was easy to print. I'll probably do up a new version that uses less material and prints faster.

Post-Printing

This of course needs a ground plane; some folks use a sheet of aluminum, I used a blank piece of copper clad PCB.

The wire support is attached using nylon screws.

This is my second ever design, mostly to learn FreeCAD. It's just built from primitive shapes: rectangular prisms (cube), cylinders, a cone, and various groupings thereof.

The base is a pancake (low, wide cylinder) with a post (tall, narrow cylinder) reinforced by a cone. The wire supports are two crossed fins (thin rectangular prisms). These parts are all joined into a union.

I then created 4 3x10mm cylinders, positioned at (+/-20, +/-20, -2.5)mm, unioned them together, and then used the cut operation to punch the base mounting holes.

The wire holes are all made from cylinders cut out from the previous shapes. To punch the holes in the wire supports, I created a 2x10mm cylinder going through a fin. I then cloned this a few times, going up 27mm (coil spacing) until I got to the top of the fin. I then created a union of these cylinders.

This union was then cloned 3 times, with each clone rotated 90 degrees and raised in elevation by 6.75mm. This gave me a right hand spiral wire path. I unioned the first and third, and second and fourth sets of cylinders, and used a cut operation to make holes through the fins.

To make the left-hand spiral, rotate the 1+3 union by 180 degrees.

To-Do

• fix screw holes for common (eg. #10) bolt sizes
• embed design information (frequency, polarization) into the surface