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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.
The antenna tuned really well on 15 meters, 20 meters, and 80 meters, but not so well on 40 meters. I tried modifying the tuning and matching by adding radials, first a pair of 33-foot
The tuner is only needed if the antenna system isn't matched (usually 50 ohm), if the antenna gives the right impedance, your setup is already complete. The tuner is usually used to make the antenna usable on the wrong bands or working wider.
9:1 voltage unun Testing the unun Connect a 450-ohm resistor to the wing nuts on the outside of the unun. Install a short length of coax between a NanoVNA or antenna analyzer and the unun to measure the resulting im-pedance. If the unun is working as it should, to transform the impedance, your instrument should measure around 50 ohms at the coax.
12 sie 2016 · A 9:1 unun is a transformer that reduces the impedance at the input by a factor of 9. So, if you connect a length of wire that presents an impedance of about 450 Ω to the input, you’ll get an impedance of about 50 Ω on the output. In fact, the 9:1 unun that I built is actually an autotransformer.
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.
I've used a "random", or better labeled as a non-resonant, wire antenna with a custom built 9:1 matching transformer for years. The trick is making sure that your radiator length is non-resonant otherwise you've made a endfed half wave and need a 64:1 transformer to match impedances.
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