4:1 Balun for folded dipole

After making a batch of nice folded dipole elements on my diy jig, I needed to work out how to mount them and  feed them with 50 Ohm coax. The feed point impedance should be 200 Ohms so I needed a 4:1 balun.

A 4:1 coax balun is easy to make and, using this tool, I worked out the size of the coax loop for my balun centred on 434.000 Mhz.

You will need

length of RJ58 coax
Maplin project box – Order code SC78K
BNC socket
Silicone sealant

Step 1

Drill holes in the project box to suit the elements of the dipole, the bnc socket and the coax balun.

Step 2

Insert the element, BNC socket and both ends of the balun.

Step 3

Solder the parts together as per the balun diagram.

Step 4

Apply a small amount of silicone to the areas around the holes in the box.

Step 5

Screw the box cover into place


A professional looking folded dipole ready to mount and use.

3 Replies to “4:1 Balun for folded dipole”

  1. Hi, I’m in the process of building a folded dipole with a 4:1 balun centered on 437.2MHz for a college project. I am writing you to ask if you have any performance data for the folded dipole shown on this page. I ask because my 4nec2 simulations for a resistance of 200ohms do not agree with the dimensions of your folded dipole. At 437.2MHz 4nec2 optimizes my length at 242mm.

    Thank You,

    P.S. my professor’s call sign is WB9AWX

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