3D Printing HF Portable

Build the K1FM-Loop

The latest version of the K1FM-Loop is electrically similar to the previous one, but it is designed around off-the-shelf parts or, more generically, items you can readily order online.

This antenna relies – heavily – on 3D printing. Acquiring the non-printed parts and assembling them should be fast and easy as no reworking at all is necessary. The needed tools are screwdrivers, wrench keys and a soldering iron. You also need a 3D printer, of course, or at least access to one.

Lets’s start from the parts list:

The antenna is composed of three parts that I am going to describe separately. They are:

  1. Capacitor assembly
  2. Radiator / Exciter assembly
  3. Supporting structure

Let’s see them one by one:

Capacitor assembly

First of all, you need to print the necessary 3D printed parts. It might be opportune to print the Dial Bushing in a different color, in order to make more visible against the rest of the box.
I printed the box in PETG because of the enhanced mechanical and thermal characteristics. ABS would also be opportune I think, or even PLA (provided you are careful not to leave it inside of a burning car).

As the print goes, you can start working on the other parts.
All you need to do is solder a piece of cable on each gang terminal, on opposite sides. Terminate the cable extensions with a ring contact, like so:

Optionally, you could solder the same extension on the center connector of each SO239. This will allows to use the center conductor as part of the radiator (Do I think this is useful? I don’t, but I’m going to do it to avoid the complaints). Here are the connectors, ready to be used:

Now you can begin assembling the box.