High frequency inductor branch ring coil

Ring coils to form a tuned circuit for radio reception in a selected wavelength range. In combination with a rotating capacitor the tuned circuit could be formed with this in steps adjustable self-induction coil. The sound volume and tuning sharpness were improved in 1920 by this low-capacitance structure. The damping is low, the volume and weight reduced to a minimum. Technical details: Palmwood cylinder with a diameter of 70 / 37mm, height 64mm. Two brass angle pieces of 20mm x 16mm are mounted at the base. Five milled grooves of 4mm wide for coil windings of white silk bobbin thread. Each winding is connected to a groove brass clamp block and connected which are interconnected, so that four branches can be made.