Archive for July 9th, 2010

Balun using Transmission Lines

9 July, 2010

This is a balun 1:1 using exclusively transmission lines (in this case Coaxial Cable).

It uses a labmda/2 line lenght to create a different of phase of 180º that compensates the 180º of the dipole and we get a relationship of 4:1.

Two sections of lambda/4 are been added to get a final relationship of 1:1. 

This balun only is valid for monoband antennas (or multibands with a multiple of 3 lambdas). And BW of adaptation (dipole+balun) is aprox. 5%.

I like this balun because you can design it with a good accurate.

Remember that:   lambda_cable  =  lambda_air x Speed Factor

Usually, Speed Factor is 0.67 for Rg-58 CU or RG-213. This parameter appears in the cable specifications.