![]() ![]() A change of either variable changes both the series resistance and the series reactance, and this becomes a trial-and-error exercise. In the past, while watching the series impedance with an antenna analyzer, we had adjusted the lengths of the tips of the driven element and the location of the shorting bar on the hairpin to decrease the SWR. This can often be achieved by adjusting the length of the driven element then the shunt inductor transforms it to 50+j0Ω. The beta match requires the antenna have a series resistance of <50Ω, and a negative, or capacitive, reactance. The beta match can be a conventional shunt coil, or in our case a parallel shorted transmission line (or hairpin). After the antenna model was completed for the 20 meter mult antennas and the first antenna was built, we matched it to 50Ω using a hairpin or beta match. ![]()
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