| 摘要 |
An antenna comprises a vertically polarized omni-directional radiating element. The radiating element may include: a tuning whip portion 1 of adjustable length; upper and lower helix portions 2, 4; an impedance transformer 3 and a fed point 5. The feed point 5 may be located off the centre of the antenna, with the upper portion 1, 2 being two thirds of the antenna length and the lower portion 4 being one third of the length. The lower coil portion 4 is arranged with a pitch which is half that of the upper portion 2. The radiating element may be a single or multiple frequency band antenna. The multiple band antenna arrangement may include a number of tapped and branching formations associated with the upper and the lower antenna portions. The antenna may use a PVC or fibre-glass tube to support the antenna portions. Some branching antenna potions may be located within the support tube and some may be multifilar formations. The antenna may provide a single band antenna operating at 10 MHz with an overall length, including a counterpoise, of 3m and a footprint of only 96 cm2. The compact antenna may be used in low visibility or stealth functions. |
