After searching the internet for hours trying to find information on how to select the right iron core for the job, I kept coming across the same problem. There is a lot information on how to wind the balun but not on how to select the right core. I then came across Peter Miles’ VK6YSF website (www.vk6ysf.com) with some information on 1:1, 4:1 & 9:1 baluns.
More information is available on Peter’s website but the basic designs are below.
1:1 Ruthroff voltage Unbalance to Balance.
Used to couple 50/75ohm transmission line to 50/75ohm centre feed dipole.
Circuit diagram of the 1:1 balun.
Winding diagram of the 1:1 balun.
4:1 Ruthroff voltage Unbalance to Balance.
Used to couple 50 transmission line to 200ohm off centre feed dipole.
Circuit diagram of the 4:1 balun.
Winding diagram of the 4:1 Balun.
Used couple 50 transmission line to 450ohm end feed long wire.
Circuit diamgram of the 9:1 unun.
Winding diagram of the 9:1 unun.
The number of winding is the same for the 1:1 & 4:1 balun.
|TOROID||NUMBER OF TURNS||POWER RATING|
The 9:1 Unun uses the following: