Long Wire Antenna 1:9 Balun for 3-50 MHz (by F4HWK)

Here i present the fabrication steps for a long wire balun having a transformation ratio of 1:9. This balun is simulated with LTSpice and measured with a VNA. The power handling has also been tested with a 50 W (SSB) of injected power without any problems.

Simulation results are available on my blog : http://kavea.free.fr

• Ferrite toroids FT114-61 (2 pcs)
• Copper wire, 1 mm diameter, 35 cm length (3 pcs)
• RF connector (e.g. SO239) (1 pc)
• Butterfly screw (1 pc)
• Any enclosure box (1 pc)

Wire winding should be done around two FT114-61 toroids (cf. photo) with the respect of the scheme (cf. photo). Wires should have some isolation coating (e.g. enameled wires).

In my case i used a 50 mm diameter PVC tube to enclose the balun. Solder corresponding wires to the RF port and to the butterfly screw (cf. photo). Now the balun is fully assembled.

To check the transformation ratio of 1:9, the balun has been measured with a VNA. In this measurement the balun is connected to a 470 ohms resistor (the impedance of the VNA port is 50 ohms).

As we can see on the picture, the balun assure a bandwidth going from 3 MHz up to 50 MHz with the respect of SWR of 2:1.

The balun has been tested with an output power of 50 W without any problems.