Horizontal Rhombic Antennas * 



By E. BRUCE, A. C. BECK and L. R. LOWRY 



The paper discusses the theoretical methods employed by the authors 

 in dimensioning horizontal rhombic receiving antennas. Experimental 

 proof is given of the engineering accuracy of the directivity calculations on 

 which this work is based. There are included brief descriptions of the 

 antenna-to-transmission line coupling circuits and the resistance terminations 

 for rhombic antennas. 



Introduction 



AN introductory discussion has been given in a previous paper ^ of a 

 type of antenna which maintains a desirable degree of directivity 

 throughout a broad continuous range of frequencies. This structure 

 was descriptively termed the "diamond-shaped" antenna in that 

 paper, but has since become known as the "rhombic antenna" and will 

 be so designated here. 



This paper discusses, in some detail, the theoretical methods 

 employed by the authors in dimensioning horizontal rhombic receiving 

 antennas from data obtained by preliminary surveys of the incident- 

 plane angles of wave-arrival at the proposed receiving site. 



Experimental proof is given of the engineering accuracy of the 

 directivity calculations on which this work is based. Checking 

 measurements were made on small-scale rhombic antennas operating at 

 correspondingly short wave-lengths. Confirming data were also 

 obtained on large, adjustable rhombic antennas during the reception of 

 European signals. 



The paper also includes a brief discussion of the antenna-to-trans- 

 mission line coupling circuits employed and, in addition, the resistance 

 terminations, located at the end of the antenna remote from the 

 receiver, used for suppressing standing waves and promoting uni- 

 directivity. Some of the performance curves obtained on these 

 devices are reproduced. 



Antenna Dimensions 



Before designing any highly directive receiving antenna system, it is 

 desirable to have a knowledge of the direction of arrival, the angular 

 spread, and the angular variation in direction of the waves to be 



* Published in Proc. I. R. E., January, 1935. 



^ " Developments in Short-Wave Directive Antennas," by E. Bruce, Proc. I. R. E., 

 August, 1931; Bell Sys. Tech. Jour., October, 1931. 



135 



