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The heart of the Un-un uses a Type 43 [FT240-43] core and consists of a trifilar [3 wire] winding arrangement around the core. The wires are wound to create a 9:1 transformer and would ideally suit an end-fed long wire antenna fed against ideally – a good counterpoise, or a good radial system.
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.
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.
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.
21 maj 2022 · With no goals and constraints, here is a coaxial wound 9:1 UnUn. Performance is very poor. and also. The first link shows the typical 9:1 UnUn while your second link is about BalUns. I assumed from the title, the goal was to make an UnUn. Specifically a 9:1. The OP was only testing from 3-30MHz, with a worse case VSWR of 1.4:1.
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.
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.
