published by N3AC on Mon, 2022-01-03 00:02
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. The beta match can be a conventional shunt coil, or in our case a parallel shorted transmission line (or hairpin). The beta match requires the antenna have a series resistance of <50Ω, and a negative, or capacitive, reactance. This can often be achieved by adjusting the length of the driven element; then the shunt inductor transforms it to 50+j0Ω.
published by nr4m on Sun, 2022-01-02 20:16
This is an attempt to explain the whole story of this antenna from start to finish, so that readers might have a better idea of how it all works together. Building a high performance antenna system is not about any one thing, but many things, which all have to work correctly. Construction began on the NR4M multi-multi contest station, also known as ‘The Goat Farm’, in the year 2000, and covers an area of 68 acres (24.8 hectares).
10 Meters:
125 feet of 45G with tweeked Hygain 105's @ 30/60/90 feet, non-switchable and fixed on EU. Another 105 at 125 feet, which is fully rotatable.
A pair of 6 element, NR4M design, yagi's, non-switchable and fixed to SA. These are mounted @35/70 feet on the 40 meter tower.
Low rotatable 5 el Hygain on 72 foot crank-up for use in domestic contest ~ 40feet.
