3

I need to build another 9:1 unun and I start searching for my toroids... (I have build 2-3 something like 4 years ago)... In parallel I checked on Google about the correct toroid etc so I found 2-3 pages with designs. My focus is on power loss as I run QRP on batteries.

9:1 voltage unun using a L15 ferrite core

9:1 Voltage Unun - FT240-61

9:1 voltage unun using a T-200-2 powdered iron toroid core

What do you think regarding power losses and materials? Which toroid should I use? (I already have the *-61 and the *-2).

Regarding wires for the turns, some use enameled copper wire, some 3-colour for like a power socket.

The unun is not for portable. So a size 200-240 is okay for some future proofing.

If I can get ok losses down to 80m, I'll be very happy, I mainly use 15 to 40m.
It's for a “random wire” end fed. Probably around 58ft max. Or maybe 53ft (space restricted)
Mike Waters
  • 7,843
  • 4
  • 16
  • 50
OHTO
  • 149
  • 3
  • Welcome to this site! The [balun] tag [also covers unun](https://ham.stackexchange.com/tags/balun/info), so I added that. – Mike Waters Feb 20 '20 at 21:55
  • This is for an end-fed antenna, right? Is it the same antenna for all those bands? How long is it? – Mike Waters Feb 21 '20 at 02:19
  • 1
    Its for a “random wire” end fed. Probably around 58ft max. Or maybe 53ft (space restricted) – OHTO Feb 21 '20 at 07:43
  • You might find [this similar question and the answers](https://ham.stackexchange.com/questions/12389/do-i-need-an-91-unun-for-a-half-wave-end-fed) particularly useful. On some bands, a 9:1 transformation ratio (50 ohms to 450 ohms) might not be optimal, as the feedpoint impedance might be much higher or much lower than 450 ohms. – Mike Waters Feb 21 '20 at 13:36
  • I copied your comment with your antenna info into the answer. Note that comments are not searchable, and such details should be in the answer itself. – Mike Waters Feb 21 '20 at 13:56

0 Answers0