Magnetic Long Wire UnUn 9:1

 

These are usually called a Magnetic Longwire Balun. Its really an impedance transformer (9:1) to feed a high impedance long wire (~450 ohm), down to a 50 ohm unbalanced coaxial input. I have heard them called an UnUn which seems more appropriate. I almost bought one of these for around 30, but then decided to make one. The toroid is a T130-2 Iron Powder core, with 3 x 9 turns of 18SWG enammeled copper wire, and the connections can be seen below.

9:1 Magnetic Wire Balun Core
The T130-2 Torroid Core

9:1 UnUn Balun Schematic Diagram