4:1 (200:50 ohm) Transformers - Yet Another Suggested Core

So this core is surprising but bang for buck is pretty amazing. It's quite small but 8 bifilar turns spaced around the core is useful from 160m (just) to 6m.

8 bifilar turns

 Perhaps you have the patience to use more turns of still finer wire?

 

12 bifilar turns

But glue, or hold while you start winding, two side by side and wind 7 bifilar turns using fine wire also results in a good transformer:

Given the extra time it takes to work with these small cores it might be false economy. But it does remind me how useful the nanoVNA is for making such measurements of unknown components. And these ferrites are really low cost.

Details of power handling and loss soon.

73's

Richard