[TowerTalk] Coax, conduit and toroids

Steve Hunt steve at karinya.net
Wed Jun 27 09:59:10 PDT 2012

Jim's comment should not be misunderstood. A 1:1 choke balun feeding a 
_perfectly_ balanced load does not have zero common-mode voltage across 
it; the choke CM voltage will be exactly half the voltage across the load.

If we gradually unbalance the load in one direction the choke CM voltage 
reduces and becomes zero when the load is completely unbalanced. If we 
unbalance the load in the other direction, the choke CM voltages 
increases and in the limit will equal the load voltage.

Steve G3TXQ

On 27/06/2012 17:08, Jim Brown wrote:
> My bifilar choke designs (which are simply a short length of parallel 
> wire line wound around a single #31 toroid) will handle full legal ham 
> power levels if the common mode voltage is reasonably low -- that is, 
> if the system is reasonably close to balance -- and they are excellent 
> chokes. 

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