A MULTIPLE UNIT STEER ABLE ANTENNA 



353 



microfarads. When spaced regularly at 60-foot intervals these capaci- 

 tances have a somewhat cumulative effect at frequencies for which 60 

 feet (18.3 meters) is a multiple of the half wave-length. Sixty feet, 

 when increased by the line velocity ratio, corresponds to 7.7 and 15.4 

 megacycles. Clearly, line sections which are not short compared with 

 the shortest wave-length should be made unequal so that joint irregu- 

 larities will not be harmful. The smaller variations of the order of 

 ±10 ohms may be due to random eccentricities produced by slight 

 buckling of the inner conductor between insulators. With the possible 



O 90 



z 



50 



40 



-40 



-80 



■120 



9 10 II 12 13 14 15 16 



FREQUENCY IN MEGACYCLES PER SECOND 



Fig. 9 — Impedance measurements made upon the 1000-meter line terminated in a 

 resistance of 78 ohms. The reactance is expressed as shunt capacitance, negative 

 values meaning an inductive reactance numerically equal to the corresponding 

 capacitive reactance. 



exception of the two large variations this line is sufficiently smooth for 

 use in a MUSA, as both theory and subsequent experience indicate. 



Input Circuit and First Detectors 



The MUSA system imposes requirements upon the input circuits 

 and detectors which do not apply to conventional receivers. These 

 requirements are as follows: 



(1) The circuits must suppress standing waves on the transmission 

 lines. ^* 



^''This requirement was more easily met than the alternate requirement men- 

 tioned in footnote (11). 



