Broadband transformers

Lot of interesting readings on the net but here some results from simulation for LOW FREQUENCY response

First of all a simple design schematic for building reference

And here some results on center frequency.

First of all a 1:2.25

When matched 1V signal source with 50ohm internal resistance must be 0.5V on node 4. (see V6 and V4)

Here is a 1:9

Here is a 1:4 step-up and step-down transformer

Here Unbalanced / BalUn different connection and effect