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[TowerTalk] current balance in ladder line?

Subject: [TowerTalk] current balance in ladder line?
From: Grant Saviers <>
Date: Sun, 16 Jan 2011 19:48:58 -0800
List-post: <">>
I'm using a ladder line fed 80m dipole as an all band antenna with a 
tuned length of line, high Z 1:1 choke at the LL to coax junction.  One 
assumption in these antennas kinda baffles me, so here is a question for 
tower-talkians with expertise in transmission lines and baluns:

Why is the current into the antenna balanced?  If I adequately choke the 
coax at the ladder line junction the current should be balanced there.  
Theory says ladder line doesn't radiate IF the current is equal (must be 
equal in phase and amplitude I assume)  in both wires, but it will get 
unbalanced if one side is near metal, etc.  So what happens on the 
ladder line if the antenna is not balanced at the feedpoint?

Is there such a device as a ladder line balun ala the baluns used to 
drive ethernet twisted pairs? (seems like a similar problem but at 100 
ohms pair Z, a ferrite 1:1 current balun is not difficult to build).

Grant  KZ1W


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