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

Step 1: Materials

• 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)

Step 2: Wire Winding

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).

Step 3: Enclosure Box

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.

Step 4: Measurements

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.