Another example of the type as used in mobile communications is "spaced constant turn" in which one or more different linear windings are wound on a single former and spaced so as to provide an efficient balance between capacitance and inductance for the radiating element at a particular resonant frequency. Many examples of this type have been used extensively for 27 MHz CB radio with a wide variety of designs originating in the US and Australia in the late 1960s. To date many millions of these ‘helical antennas’ have been mass-produced for mainly mobile vehicle use and reached peak production during the CB Radio boom-times during the 1970s to late 1980s and used worldwide. Multi-frequency versions with manual plug-in taps have become the mainstay for multi-band single-sideband modulation (SSB) HF communications with frequency coverage over the whole HF spectrum from 1MHz to 30 MHz with from 2 to 6 dedicated frequency tap points tuned at dedicated and allocated frequencies in the land mobile, marine and aircraft bands. Recently these antennas have been superseded by electronicly tuned antenna matching devices.