[TowerTalk] Step-down balun 12.5-50ohm

[jimlux]

Robert Thain wrote:
> Hello,
> 
> I'm looking to build a Step-down balun 12.5-50ohm ie input with 50ohm coax and output to 12.5ohm wire. 
> 
> Can any one point me in the right direction for a plan. I know they exist I've seen them for sale.
> 
> I have bought a 1:4   50ohm - 200ohm balun, but I think I've messed up, its the "wrong way around".
> I hope I can use it for parts. 
> 
> Thanks

both of those are 2:1 turns ratio. You just need to flip it around.  For 
your application, the coax (50 ohm side) goes to the winding with more 
turns.