RADIO EXTENSION LINKS TO TELEPHONE SYSTEM 635 



element consists of a conductor, whose length is an integral number of 

 half wave-lengths, bent in such a way that the currents in all of the 

 vertical elements will be in phase while in the horizontal elements 

 they will largely balance out. The vertical elements are all placed in 

 the same plane and the horizontal elements depart from that plane 

 only enough for crossing without short-circuiting. With this arrange- 

 ment the energy radiated in a direction perpendicular to the paper 

 will be a maximum. It will be a minimum in the plane of the paper in 

 side or vertical directions. Any suitable number of these elements 

 may be arranged in the same plane and connected together so as to 

 increase the energy in the desired direction. Inasmuch as the length 

 of the wire and the configuration into which it is bent are associated 

 with the frequency, an antenna constructed for one frequency is not 

 usable at another. This is true in any antenna where standing 

 waves exist. 



In the antennas of this type which have been used on our short- 

 wave circuits for operating across the Atlantic, as many as 8 elements 

 were connected in parallel in the same plane so as to radiate in the 

 desired direction producing a sharp directivity pattern. At the same 

 time another set of 8 elements were located one-half wave-length away 

 parallel to the first as indicated in Fig. 15 so as to eliminate the radia- 

 tion in one of the two directions perpendicular to the screen. This 

 causes all the energy to be radiated in the desired direction. For 

 operating one radio transmitter on a transoceanic circuit it is necessary 

 to have three or four antennas for each transmitter, one for each wave- 

 length. These antennas were strung between towers. Figure 16 

 shows the antennas as used formerly at Lawrenceville, New Jersey. 

 One antenna occupied two inter-tower spacings. The direction of 

 transmission is perpendicular to the line of the towers. 



At the receiving end directive antennas are also used. An ele- 

 mental picture is shown in Fig. 17 of the receiving antenna devised 

 for this purpose by Mr. E. Bruce.'' The third diagram shows the shape 

 into which a long conductor is bent and the arrows show the instan- 

 taneous directions of current flow at a moment of maximum. It is 

 observed here also that in all the vertical elements the currents flow 

 in the same direction while in the horizontal elements enough flows in 

 the two directions so the effect is neutralized. This antenna will 

 therefore also receive or transmit in the directions perpendicular to the 

 plane of the conductor and not in directions within the plane. This 

 type of antenna can also be constructed with a reflector behind it to 

 reduce the direction of transmission or reception to a single direction. 



