When winding an unun


If you stack toroids, the power handling is determined by the cross section the wire goes round.





What happens when you take two stacks, put them next to each other binocular fashion, and wind around the centrer part




Both the above are ununs tacked together to illustrate the question (so don't look at the soldering ), both have the same transformation

Guess no one else knows either!

Dunno Steve, hook it up to an aerial, shove 400W up it and if it doesn't cook then your design works.
The last Balun I made for HF I used a ferrite rod, it overheated and bent itself into a banana shape, needless to say I sacked off HF saucery and focused on VHF antenna systems - much more success.

Would think it's down to the volume you have in the core ,more core more power

The temperature rise depends on the surface area more than the volume. The volume will determine how quickly it heats up, but the surface area tends to determine the final temperature.

Steve G3TXQ