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.