The current 600M antenna is constructed of 67 ft (20.4m) of aluminum tubing. Top loading is accomplished with eight (8) 35 ft (10.7m) wires connected to the top and sloping outward. More base loading is required than with the previous wire “T” antenna. Fine tuning is handled via a variometer that is remotely controlled by an autotuning system consisting of a microprocessor (Arduino) reading power, SWR, impedance and phase data from an LP-100A wattmeter with an MF coupler. The Arduino drives the variometer motor via an H-bridge IC (L293D).
Estimated efficiency is around 12-13%. This is a result of the antenna being tied into the 160M Four-square radial system, consisting of 22,000 ft of #16 copper over a 350 ft x 350 ft area, providing about 6-7 ohms of ground loss.
A 410 uH coil (6 in. diameter, #12 copper) in series with a 1000 pF vacuum variable tunes the vertical to resonance. A 10uH roller inductor is configured as an autotransformer for impedance matching, one end grounded, the other end connected to the vacuum variable, and the roller connected to the coax center conductor.