| 摘要 |
769,080. Aerials. LANDER, D. E. R. May 18, 1955 [May 22, 1954], No. 14347/55. Class 40(7) An aerial for high frequency signals comprises a helical conductor 2 which has 'extending from it a number of pairs of rods, the rods being connected at spaced points along the helix. The pairs of rods (e.g. 6a, 6b) together with the intervening portion of conductor 2 form circuits tuned to a frequency approximating to that of the signal and the feed 11 is connected across a portion of the part of the helix disposed between two pairs of rods. The helical conductor is supported round a metal rod 1 on insulators 3 and and is preferably formed of metal strip wound edgewise. The rod elements are carried by movable insulating brackets 12 and may be secured to'the conductor 2 by suitable contact clips. Each rod may be of telescopic construction. As shown the rods 6a and 6b and the turns N 1 form a first tuned circuit whilst the rods 6c and 6d and the turns N 2 form a second tuned circuit. Between these there are the turns N 3 and with rods 6b and 6c these form a third tuned circuit. All these circuits may be tuned to the same frequency, or they may be tuned to slightly differing frequencies to increase the bandwidth. The number of the turns N 3 across which the feeder 11 is tapped off is so chosen as to match the aerial to the feeder. The support rod 1 may be insulated from the mounting means and provided with a separate down lead 10 so that it can be used as an ordinary broadcast frequency aerial. If required it may be provided with a telescopic top extension member 4. Alternatively the member 4 alone may be used as the aerial for these frequencies. In a modification the rod 1 and/or extension member 4 serves as a dipole for shortwaves and signals may, it is stated, be received by means of this dipole if it is not tuned to their frequency provided one or more of the helical conductor and rod circuits is so tuned. The helical conductor 2 may be used as an aerial if desired and the down-lead 10 connected thereto. In another variation the rod 1 and/or the extension 4 may be grounded as a protection against lightning. If it is preferred not to earth the member 4 directly a spark gap may be arranged between it and the grounded member 1. The rods 6 of the helical conductor and rod aerial system may be arranged in V formation, or bent so that the aerial is capable of receiving vertically polarized signals. A pair of rods 6e and 6f with the intervening portion of helical conductor may be tuned to act as a director to the aerial formed by the tuned circuits A, B and C. A separate director circuit such as that shown separately in the bottom corner of the drawing may be placed on the lower part of the rod 1 below the aerial. The helical conductor 9 of this circuit is wound in the opposite direction to conductor 2 although it may be wound in the same direction if sufficiently spaced 'from the end of 'conductor 2. It is also possible to form a reflector on an extended part of conductor 2. An array of aerials according to the invention may be mounted on a single rod 1 and coupled to a common feeder. The section of the helix comprising the turns N 3 together with the rods 6b and 6c may form an aerial for a required high frequency channel with the rods 6a and 6d acting as director and reflector respectively. |
