﻿644 
  

  

  Messrs. 
  E. 
  Bellini 
  and 
  A. 
  Tosi 
  on 
  a 
  

  

  of 
  the 
  bilateral 
  directive 
  system 
  already 
  described 
  is 
  composed 
  

   o£ 
  two 
  equal 
  tangent 
  circles, 
  and 
  the 
  one 
  half-field, 
  repre- 
  

   sented 
  by 
  one 
  of 
  the 
  circles, 
  is 
  opposite 
  in 
  phase 
  to 
  the 
  other 
  

   half-field. 
  

  

  If 
  one 
  operates 
  simultaneously, 
  at 
  the 
  same 
  station, 
  both 
  

   the 
  directive 
  system 
  and 
  an 
  ordinary 
  system 
  giving 
  a 
  circular 
  

   emission, 
  whose 
  vertical 
  antenna 
  is 
  symmetrically 
  placed 
  

   with 
  reference 
  to 
  the 
  directive 
  aerial, 
  the 
  resultant 
  electro- 
  

   magnetic 
  field 
  of 
  the 
  simultaneous 
  emissions 
  of 
  the 
  two 
  

   systems, 
  can, 
  in 
  general, 
  be 
  obtained 
  by 
  vectorially 
  adding 
  

   the 
  partial 
  diagrams 
  of 
  the 
  two 
  systems. 
  

  

  As 
  an 
  example, 
  let 
  a 
  x 
  and 
  a 
  2 
  (fig. 
  1) 
  be 
  the 
  two 
  tangent 
  

  

  0-75 
  

  

  0-59 
  

  

  0-4-1 
  

  

  025 
  

  

  circles 
  forming 
  the 
  diagram 
  of 
  the 
  electromagnetic 
  field 
  of 
  

   the 
  directive 
  system 
  ; 
  the 
  circumference 
  b 
  represents 
  the 
  

   diagram 
  of 
  the 
  system 
  with 
  circular 
  emission, 
  of 
  amplitude 
  

   equal 
  to 
  the 
  maximum 
  amplitude 
  of 
  the 
  directive 
  system 
  ; 
  

   let 
  the 
  phase-difference 
  between 
  b 
  and 
  a 
  x 
  be 
  zero, 
  and 
  that 
  

   between 
  b 
  and 
  a 
  2 
  180°. 
  The 
  resultant 
  diagram 
  c 
  is 
  obtained 
  

   in 
  this 
  case 
  by 
  adding 
  algebraically 
  the 
  radii 
  vector 
  es 
  of 
  the 
  

   curve 
  a 
  x 
  to 
  those 
  of 
  the 
  diagram 
  b 
  and 
  by 
  subtracting 
  the 
  

   radii 
  vectores 
  of 
  the 
  curve 
  b 
  from 
  those 
  of 
  curve 
  a 
  2 
  . 
  The 
  

   resultant 
  diagram 
  is 
  represented 
  by 
  a 
  " 
  cardioid." 
  

  

  