Topband: Wideband x-former...

[Richard (Rick) Karlquist]

k3bu at optimum.net wrote:
>> 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...

My MonstIR Yagi has a 50 ohm to 22 ohm balun that is good from
7 MHz to 54 MHz (I measured it on a network analyzer).  In your
case, you only need an "un-un" not a "bal-un".  Even easier.
You can simply get a big 43 matl toroid and wind an autotransformer
on it.  Make a tri-filar winding and connect the three wires
in series (end of first wire to beginning of second wire, etc).
Then connect the high impedance side across the 3 wires in
series and connect the low impedance side across just 2 of
the wires.  Use fairly large wire (14 to 18 gauge) with thin
insulation, to minimize leakage inductance.

Rick N6RK