Better Balun Boxes

I did an instructable on building a Balun or Unun. A lot of people seemed to like it and it get getting repined in every bodies emergency go pack or field day kit bag. Since those boxes were out of stock I went to the Home Depot to see what kind of PVC electrical boxes they had.

There's a good selection but the boxes with no holes start around $8. Some of the ones with a conduit fitting molded in are under $2. No easy way to plug that without a big protrusion so I decided to make use of them.

Step 1: Custom 3D Printed Bushings

Better Balun Boxes
Better Balun Boxes

I made some bushings in OpenScad for some common parts like an SO-239 and some binding posts. I grabbed a bunch of different boxes with different configurations and some covers. I used PLA material and it seems to bond well to the boxes with standard PVC Conduit Cement.

Step 2: SO-239 Bushing

Better Balun Boxes
Better Balun Boxes

This was the first one I needed. I made a small relief for a ground wire under one of the screw holes. A little RTV will seal it but since I usually have this one pointed down I don't worry about that....

Better Balun Boxes
SO239 Bushing.scad1001 bytes

Step 3: 1/4-20 Posts for Wing Nuts

Better Balun Boxes
Better Balun Boxes
Better Balun Boxes

These are pretty solid posts with a 1/4-20 hole down the center for a standard bolt. Use Stainless hardware if you are bored. I just use some automotive dielectric grease on the exposed metal. I bet a shot of Battery terminal spray after your wired up would work too.

I made these with a 50% infill and 6 shells to make them stiff enough to handle my overenthusiastic wrench use. maybe I'll make a recess for the nut on top but I do like to "KISS"

You can strap this to the top of a pole and hang an inverted Vee directly off the terminals.....

Better Balun Boxes
screw lug bushing.scad325 bytes

Step 4: Binding Post Bushings

Better Balun Boxes

Just a hollowed out version of the wing nut bushing. Good for light duty use or small go packs.Much prettier than the wing nuts but I wouldn't hang a dipole off these without some other support. The hollow and thin brass will snap.

Better Balun Boxes
binding post bushing.scad338 bytes

Step 5: Other Uses

Better Balun Boxes
Better Balun Boxes
Better Balun Boxes
Better Balun Boxes
Better Balun Boxes

There are tons of other uses I can think of. Pilot lights, switches, headphone connectors, etc.

These tiny bushings have a ridge on top that can hold standard wire strain relief fittings. I used one on the power cord of this simple knife etching power supply.

Better Balun Boxes
pvc conduit plug.scad189 bytes
Better Balun Boxes
Strain Relief 2.scad342 bytes
Better Balun Boxes
strain relief bushing.scad207 bytes
 
 

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