BNC Transformer Spacer

Disclaimer:

I have no affiliation with Adam Kimmerly (K6ARK). I just like his stuff, and his kits were out of stock, so I made this. You should check out his stuff if you haven't. 

For this transformer, you'll need:

FT50-43 Ferrite Toroid

Male BNC - Thru Hole - Vertical PCB Mount (ground pins in a 6.6mm square)

Magnet wire. I used 28 AWG BNTEChGO, Red, 155C.

Thin, strong wire. I used PolyStealth 26 AWG.

Heat Shrink Tubing

Anything else your transformer design requires (capacitors, etc)

Optional:

2mm Mini Banana plugs and sockets to disconnect your radiator from your transformer. 

Hot Glue to pot the transformer

Directions:

Wind whatever transformer you want (balun, unun, 1:1, 4:1, 9:1, 49:1, 64:1, whatever). Lots of information elsewhere on the web on impedance matching transformers. Try to have the wire for BNC center pin in the middle of the toroid, and the wire for BNC shield on the outside. 

Solder the ground/shield wire to one of the BNC ground lugs. (Optional, also solder on a small piece of wire with a mini banana socket for a counter poise).

Insert the spacer. 

Solder the center pin wire to the center pin.

Stack the toroid on the spacer. 

Solder the PolyStealth to the antenna wire on the transformer and weave it through the holes in the strain relief (up-down-up). (Optional, add a mini banana socket, so you can disconnect your radiating element. Also prevents damage by just unplugging if it gets pulled). 

(Optional, fill the toroid with hot glue before pressing the strain relief plate on top. 

Trim and apply some heat-shrink tubing. Note: Heating the heat-shrink may soften the 3D printed parts. Be careful not to deform them. 

Note: This is a QRP transformer. The small toroid will saturate very quickly and overheat if you use too much power, and we are using TINY magnet wire.