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Richard Clark wrote:
"I would suggest you research the "Franklin Array"." Current reverses at the open-circuit end of an antenna. 180-degrees back from the open end it reverses again. Current flowing in opposite directions begins to reduce the field strength perpendicular to the antenna when the total length reaches 5/8-wavelength. At a point 1/2-wave or 5/8-wave back from the open circuit, a phase inverter is used to produce (2) mostly in-phase antenna segments. Some ways to get in-phase segments are to drive the array at that point. Or, to connect the segments through a short-circuit 1/4-wave stub. The "Super-J Maritime Antenna" in the ARRL Antenna Book uses this method. Or, use a lumped network in place of the short-circuit stub. Kraus shows an interesting and simple phase inverter in Figure 23-21(b) on page 824 of his 3rd edition of "Antennas". The inverters are self-resonant coils. No external capacitors required. They are "traps". Best regards, Richard Harrison, KB5WZI |