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12 sie 2016 · It’s relatively easy to build a 9:1 balun. One of the most common designs is to wind nine turns of a trifilar winding around a toroid core. Trifilar means that there are three wires wound simultaneously around the core.
Uncoil the magnet wire. Start with the end of the wire in the center of the toroid and begin winding as shown in the image to the right. Make about 7-10 full turns, evenly spaced around the toroid. The starting end of the wire will solder to the “GND” pad on the PCB.
4 cze 2021 · Easiest way to find out is to build it and measure empirically. Using triple windings allows closer wire spacing between the transformer input and output (primary and secondary) windings which can improve the magnetic coupling coefficient.
These are sometimes known as a Magnetic Longwire Balun. Its really an impedance transformer (9:1) to feed a high impedance, end fed (unbalanced) random wire which is likely to be a few hundred ohms, and transform it into something closer to a 50Ω (unbalanced) coaxial input, hence UnUn.
Figure 2 Schematic of the 9:1 voltage unun. Typically unbalanced = 50/75 ohms too unbalanced = 450/675 ohms. Figure 3 Wiring of the 9:1 voltage unun. Note this drawing shows winding connections and not the number of turns required. See article for details.
The 1:9 unun is connect to an un-balanced feed line and to an un-balanced antenna with an impedance step up from typically 50ohms to 450ohms, the 1:9 Voltage unun is design using a FT140-43 Ferrite Toroid Core.
Building a 9:1 UNUN for a random-wire multi-band end-fed antenna using an FT-140-43 toroid instead of the usual T106-2. Presumably the ferrite toroid works b...
