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4 to 1 balun.
The completed balun core.

This balun was made with single ferrite core, (Jaycar L01234) wired using 9 turns of three single strands of Cat 5 UTP wire in an auto-transformer type configuration. 50 ohm primary is made from 2 x 9 turns, wired in parallel. The 200 ohm secondary is formed from the remaining single 9 turn winding. The picture here shows the completed balun core.
 
 
4 to 1 Balun
 
 
The schematic

 
 
4 to 1 Balun schematic
 
 
So, what does the balun impedance look like?

Here's the Smith chart showing the impedance from 1 to 60MHz. The marker is at 30MHz.
 
 
4 to 1 smith chart
 
 
and the return loss?

Here's the VSWR from 1 to 60MHz. The marker is at 30MHz. Yes - it is that flat!!!
 
 
4 to 1 vswr
 
       
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