Topband: Wideband x-former...

[k3bu at optimum.net]

> Hi TB'ers!
> 
> Anyone out there with experiences on wideband transformers wich 
> can handle some power?
> I've been trying to match 20 ohms to 50 ohms for a mobile whip, 
> but no success so far...
> 
> I've tried different cores, iron powder and ferrites, separate 
> windings and one tapped winding, but cant make it work. My 
> hypothesis is that a 2:1 impedance conversion would do, so then 
> the relation between the two windings should be the square root 
> of 2 ie 1,414. What am I missing?
> 
> All suggestions welcome!
> 
> 73 de Lars, SM3BDZ

 
You don't need no stinkin' ferites.
Just wind about 6 turns of copper tubing coil, insert it between the base of the whip and ground, connect coax - shield to ground and center - find 50 ohm point on the coil, about 3 - 4 turns up.
 
73  Yuri, K3BU/m