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balun 4:1

4:1 Guanella – Source: ON6RH

Balun 4:1 – 2 to 50 MHz

The inspiration for this balun comes from a Guanella design found online. After experimenting with windings and cores, this result was achieved.
Balun view
The core is an FT240‑43, purchased at LAB Electronics in Hasselt for a little over 16 euros. After testing, 11 turns on each side proved to be the best choice, as shown in the example below.
Balun winding Balun winding 2
This balun works excellently in combination with a 40.5‑meter OCF antenna, fed at 33%. The total length may vary depending on the installation. My antenna is installed as a sloper, forming a seven‑band antenna.
Balun antenna Balun table
On the mentioned frequencies, the antenna works without a tuner. With a tuner, even 60m and 17m are possible.
Balun 001 Balun 002

SWR measurements

Below are the SWR values on 80m, 40m, 20m, 15m, 10m and 6m.
SWR 2.999 MHz
2,999 MHz – SWR 1.3
SWR 3.490 MHz
3,490 MHz – SWR 1.2
SWR 3.8 MHz
3,8 MHz – SWR 1.2
SWR 7.2 MHz
7,2 MHz – SWR 1.1
SWR 14.247 MHz
14,247 MHz – SWR 1.1
SWR 21.202 MHz
21,202 MHz – SWR 1.1
SWR 28.794 MHz
28,794 MHz – SWR 1.2
SWR 29.977 MHz
29,977 MHz – SWR 1.2
SWR 50.095 MHz
50,095 MHz – SWR 1.2