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An 80-10 end-fed half-wave antenna can be a very good performing part of an HF station. But its performance depends heavily on a well-designed and carefully constructed 49:1 unun, which matches the long wire impedance to within tuning range of operation. But the perfor-mance of an end-fed antenna is also very dependent on height above ground.
DIY. Worthwhile projects you can build on your own. The inverted-L Rybakov 806 antenna. The what? I’ve been looking for a good inverted-L antenna design that I could build, and hap-pened upon this version, which seems to have not only operator testimonials but technical data to support them.
Coil assembly. The diagram to the right shows what we're trying to accomplish. The pur-poses of this design are to maintain a 50-ohm impedance transformation on the transceiver side of the unun for a wide range of frequencies on 100 watts of transmit power.
12 sie 2016 · Your unun has integral numbers of turns in its primary (9 turns between the counterpoise and the radio tap) and an integral number of turns in the secondary (27 turns between the counterpoise and the antenna with 9 of the turns common to both primary and secondary).
referred to as an Unun – unbalanced to unbalanced matching transformer. The next component is the coax feedline coming from the radio. Typically, this is a 50-ohm, low loss coax cable that feeds the antenna system. The last component is the counterpoise, which is cut for 0.05 λ (wave length).
This project assembles a 49:1 ferrite-core (“FT”) type #43 transformer that matches 50 ohm input to 2500 ohm end fed antenna. It is optimized for 3.5/7/10/14 MHz but will work reasonably well on all amateur bands from 80 meters thru 10 meters with a 135 foot length of wire and a short connection to ground.
4 kwi 2020 · These are all variations on a lossy transformer. Alpha and Chameleon don’t actually tell us that, but the broadband SWR charts tell the story. An efficient antenna has sharp SWR dips at resonance. Resistive losses make those very broad. The classic design of this sort is the Comet CHA-250B.
