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Baluns for 25 and 150 ohm
Final project

Another balun box ready for use.
 
 
Balun breakout box #2
 
 
Balun construction.

The various baluns are made with 2 x ferrite cores, Jaycar LF1258 taped together to form a figure eight core (side view). The wire used is from Category 5 data cable. The type of wire provides good insulation between wires and allows the correct amount of interwinding capacitance between the turns to give us the desired response characteristics we're looking for in a balun.

 
 
2 to 1 Balun
 
 
Here's the Smith chart for the 50 to 25 ohm auto-transformer.

Here's the Smith chart showing the impedance from 1 to 30MHz. The marker is at 3.6MHz.
 
 
1 to 2 Smith chart
 
 
The 50:25 return loss.

Here's the VSWR from 1 to 30MHz. The marker is at 3.6MHz.
 
 
1 to 2 vswr
 
 
Here's the schematic for the 50:150 ohm auto-transformer.

 
 
1 to 3 Balun
 
 
Here's the Smith chart for the 50:150 auto-transformer.

Here's the Smith chart showing the impedance from 1 to 30MHz. The marker is at 30MHz.
 
 
1 to 3 Smith chart
 
 
The 50:150 return loss.

Here's the VSWR from 1 to 30MHz. The marker is at 30MHz.
 
 
1 to 3 vswr
 
       
    2006 - 2009 S.Spirat 
Another SPIRAT initiative