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I need to convert 75 ohms balanced impedance to 50 ohms unbalanced impedance using a balun. How do I do that? I am new to this and don't really understand the concept of a:1 voltage and current baluns.

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To clarify your confusion, some transformers have isolated primary and secondary windings. Some don't and have only one winding with a third tap-off point. These are cheaper to manufacture and can be used where isolation is not required. In power transformers they're often used to step the mains down say, from 230 V to 115 V or similar.

schematic

simulate this circuit – Schematic created using CircuitLab

In your case you have a balanced signal which should feed into a balanced load. The balun provides such a load and the two halves of the balanced signal contribute to driving the unbalanced output. Notice that since you only have half the voltage on the output it will be able to deliver more current so its output impedance will be lower than the balanced signal.

I hope that helps.

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A balun stands for "BALanced-UNbalanced" so you don't want a balun you want a transformer and, the ratio of primary to secondary turns would need to be the square root of 75/50 i.e. 1.225:1.

If you have a 50 ohm resistor on the lower turns winding it will look like 75 ohms from the perspective of the higher turns winding.

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  • \$\begingroup\$ I am sorry. could you go through the question once again? It is 50 ohms unbalanced(edited that). \$\endgroup\$ –  Siddhartha rao kamalakara Oct 29 '15 at 18:43
  • \$\begingroup\$ You can still use a transformer because you can drive any winding with a balanced signal or an unbalanced signal providing the windings are isolated. \$\endgroup\$ – Andy aka Oct 29 '15 at 18:44
  • \$\begingroup\$ OP is going from balanced to unbalanced so surely a balun is appropriate? The maths and rest of the answer looks fine. \$\endgroup\$ – Transistor Oct 29 '15 at 18:44
  • \$\begingroup\$ @transistor read the comment trail and look at the edit on the question. \$\endgroup\$ – Andy aka Oct 29 '15 at 18:45
  • \$\begingroup\$ @Andyaka I was asked to use only a balun. So i am a little bit confused.I can use a balun, right?please bear with me, i am new to all this \$\endgroup\$ –  Siddhartha rao kamalakara Oct 29 '15 at 18:54

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