[TowerTalk] current balun question

[Jim Brown]

On Tue,3/14/2017 12:41 AM, Máximo EA1DDO_HK1H wrote:
> Same question in a different way is; Is the current choke forcing to 
> balance differential currents?

Hello Maximo,

An effective common mode choke forces current to near zero at the point 
where it is placed. IF it placed at the feedpoint, it will force current 
in the sides of the antenna to be equal AT THE FEEDPOINT. In effect, it 
disconnects the feedline from the antenna as an element of the antenna.

If the same choke is placed near the shack, the feedline IS part of the 
antenna, with it's electrical length equal to its physical length, with 
the choke forcing the common mode current to near zero at the point 
where it is placed in the feedline.

By "effective," I mean a choke that has a very high common mode 
resistive impedance at the operating frequency.

73, Jim K9YC