GB526417A - Improvements in or relating to directional radio transmitting and receiving systems - Google Patents

Abstract

526,417. Directive wireless systems. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., and FALLOON, S. W. H. W. Feb. 16, 1939. No. 5187. [Class 40 (v)] A directive aerial system, of the kind in which two or more pairs of "crossed" frames are spaced apart and rotated about the centre of the connecting axis, is arranged to avoid the production of " false zeros " due to night error. As shown in Fig. 2, two crossed frames a, b, and a<SP>1</SP>, b<SP>1</SP>, are mounted on a common axis d rotated around r, and are fed (for transmission) from a common carrier-source (not shown) having two outputs capable of independent modulation. The frames a and a<SP>1</SP> are fed with one half-wave of the modulated output, and the frames b, b<SP>1</SP> with the other half-wave. The arrangement ensures that only one pair of frames can give a "false zero," and this appears only as a change in tone. In Fig. 4, for instance, A represents the signal normally heard, which becomes zero only at the true minimum line (at right-angles to the connecting axis d) whilst B represents the lowered tone heard at a " false zero." The arrangement of Fig. 2 gives the desired result for the reflected space-wave, whilst that shown in Fig. 5 is used for the ground wave. In the latter case, the frames a, a<SP>1</SP> are mounted at right-angles to, and the frames b, b<SP>1</SP> parallel with the connecting axis d. The modulated frequency may be squaretopped instead of sinusoidal.