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
Results
A professional looking folded dipole ready to mount and use.
