| 摘要 |
A dual frequency vertical antenna for radiating a first and a second airwave signal in response to a first and a second conducted signal, the first airwave signal having a first frequency and the second airwave signal having a second frequency lower than one-half the first frequency. The antenna includes a horizontal base member and a vertical mast, including a coaxially disposed rod, projecting upward from the base member to a masthead. For feeding the conducted signals, a lower mast extension projecting downward from the base member and a tuning sleeve projecting either upward or downward from the base member are tuned to +E,fra 1/4+EE wavelength at the first frequency and a single coaxial cable is connected between the base member and a feedpoint on the rod. The first airwave signal radiates from a dipole formed of an +E,fra 1/4+EE wavelength upper rod extension extending upward from said masthead and a concentric +E,fra 1/4+EE wavelength upper sleeve external to the mast projecting downward from said masthead. The mast is +E,fra 1/4+EE wavelength at the second frequency for radiating the second airwave signal from a dipole formed of the mast and the base member.
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