help me in this balun

[Willen]

this is 75/300 ohm or 1:4 balun on Two-hole Ferrite core with twin wire. I want to make it 1:1 balun. Can anybody help me with schematic and details?

 

[unclejed613]

like this, using the existing balun, just changing the wiring to be a 1:1 transformer:

 

[crutschow]

What impedance do you want, 75Ω or 300Ω?
Why do you want a 1:1 balun?

 

[Willen]

What impedance do you want, 75Ω or 300Ω?
Why do you want a 1:1 balun?

I want to connect unbalanced coax to balanced 75 ohm dipole for my 5 watt FM Tx.

 

[Willen]

like this, using the existing balun, just changing the wiring to be a 1:1 transformer:

Wow!!!! Amazing!

Does coiled coax balun work as same as this balun? How many turns and diameter is perfect for coax coiled balun? Do have any idea?

 

[unclejed613]

I want to connect unbalanced coax to balanced 75 ohm dipole for my 5 watt FM Tx.

you don't need a balun for that. just connect the center lead to one half of the dipole, and the shield to the other half of the dipole. baluns (even 1:1 baluns) will introduce losses. a dipole is "balanced" even if fed with coax. all you need to concern yourself with is making sure the dipole elements are 1/4 wavelength, and the total length is 1/2 wavelength. for 1/2 wave in meters the formula for a wire antenna is 143/f, and each element is 1/2 that length. so a wire dipole for 100Mhz would be 1.43 meters, and each of the two elements would be 71.5cm. (this takes into account the 95% velocity factor of wire)

 

[Willen]

you don't need a balun for that. just connect the center lead to one half of the dipole, and the shield to the other half of the dipole. baluns (even 1:1 baluns) will introduce losses. a dipole is "balanced" even if fed with coax. all you need to concern yourself with is making sure the dipole elements are 1/4 wavelength, and the total length is 1/2 wavelength. for 1/2 wave in meters the formula for a wire antenna is 143/f, and each element is 1/2 that length. so a wire dipole for 100Mhz would be 1.43 meters, and each of the two elements would be 71.5cm. (this takes into account the 95% velocity factor of wire)

-Then what is the purpose of 1:1 balun?
-Why it is unnecessary to use balun on my coax of dipole?
-I found on many places they are using coiled coax as a 1:1 balun on their FM Tx. Is it really 1:1 balun or that is just to block SWR of antenna?