[TowerTalk] Force 12 B-1/B-1S Baluns

[Steve Hunt]

If the choke is primarily reactive, and the coax braid impedance is also 
reactive but the opposite sign, adding the choke may *reduce* the net CM 
path impedance and *increase* the braid current. Making the choke 
resistive avoids that problem.

The choke resistance doesn't need to be "sky high" in this application - 
it simply needs to be adequate! 1500W into a balanced 50 Ohm load means 
137v worst-case across the choke. Keep the choke resistance to 2k Ohms 
or more and the worst-case dissipation is a modest 9W. 2k Ohms is very 
easily realised over a wide frequency range.

73,
Steve G3TXQ


On 13/05/2013 13:30, Jim Thomson wrote:
>
> ##  why do they have to be resistive ??   Current squared  x  resistive ohms =  lotsa heat.
> Current squared  x  XL = no heat, or minimal heat.
>
> ##  If the balun is mainly resistive, it will work, but the Z has to be sky high, so you don’t cook the
> balun.
>
>