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Learn how to avoid the half wave lengths and multiples that cause high swr and tuning problems with random wire antennas. See a table of frequencies and lengths to use or avoid for optimal performance on HF bands.
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Wire Lengths for Various Band Combinations. The graph below shows lengths to avoid for different collections of bands. The fewer bands, the fewer high impedance regions to avoid. You also want the antenna to be at least 1/4 wavelength long for each band you plan to use. For instance, to work 40m be sure the antenna is at least 10m or 33' long.
Learn how to avoid the worst lengths for random wire antennas on different HF bands and find the best ones for low swr and good loading. See a table of lengths to stay away from and a list of recommended lengths based on multiples of half wave.
Learn why you should not use certain lengths of random wire for HF antennas and how to find the best ones. See a table of frequencies and multiples of half wave that cause high swr and tuning problems.
Learn how to calculate the best lengths for random wire antennas on different ham bands and modes. See graphs, formulas, code and examples for end fed antennas with counterpoise.
26 kwi 2012 · Learn how to calculate the optimal length of a random wire antenna for amateur radio bands using a PowerBASIC program. See the gaps in the quarter-wavelength frequency spectrum and the corresponding electrical lengths of the antenna.
22 kwi 2022 · The chart shown here (click for a larger view) is my attempt to calculate the relative “goodness” of any particular length of wire for an EFLW antenna. I took the centre wavelength of each band, divided it into the various antenna lengths, and marked where half wave or near half wave alignment would prevent tuning with a 9:1 UnUn.
