The current 630M / 2200M antenna is constructed of 67 ft (20.4m) of aluminum tubing. Top loading is accomplished with eight (8) wires ranging from 35-50 ft connected to the top and sloping outward with a perimeter wire connected to the ends. Resonating circuits are switched via vacuum relays. On 630M, a series inductor / vacuum variable capacitor are using, while on 2200m a variometer tunes to resonance. Impedance matching is performed with a bank of remotely switched mica capacitors functioning as a low-pass L-network. Automatic motor control for tuning to resonance can be engaged on 630m using a phase detector in the shack.
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 low ground losses. Total feedpoint resistance is typically around 6 ohms.
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.