208 BELL SYSTEM TECHNICAL JOURNAL 



ANGLE IN DEGREES 

 18 23 29 35 18 23 29 35 18 23 29 35 



HALF-WAVE VERTICAL 

 <^ = 69°-7l° <^ = 7l°-73° <^=73°-76° 



RHOMBUS 



A . . . _J\__j\_^^___ A A A A 



TIME * 



Fig. 14 — Pulse pattern changes with steering, March 8 and 9, 

 1933. Station GCS on 33.26 meters. 



to Fig. 4. Marked over the individual pulses are the arrival angles 

 above the horizontal, measured through the cooperation of co-workers. 



Figure 14 is of a test, at thirty-three meters, during a period when a 

 wide angular spread of the cluster prevailed. Four narrow pulses of 

 similar magnitude appear on the half-wave antenna. The progressive 

 effect of suppressing the higher angle waves by steering the rhombus 

 is shown. Very appreciable selective fading reductions are possible 

 under such conditions. 



Figure 15 is a sketch of twenty-meter observations during a period 



ANGLE IN DEGREES 

 '7 20 17 20 17 20 



HALF-WAVE VERTICAL 

 <>>=69°-7l° <t>= 7\°-^^° <t> = 72>°-76° 



RHOMBUS 



— TL-^ —J\j\. 



Fig. 15 — Pulse pattern changes with steering, April 8, 1933, 

 2:00 P.M., E. S. T. Station GBW on 20.78 meters. 



when selective fading reductions were achieved at the lower angle an- 

 tenna settings. The broad, flat tops of the pulses are incidentally an 

 interesting contrast to those in Fig. 14. These are possibly due to an 

 increased horizontal spread of wave angles. 



Figure 16 is of a case where it was possible deliberately to make the 

 fading on the rhombus worse than that on the comparison antenna. 

 Since the later pulse had a higher amplitude than the earlier one, 

 rhombic steering by equalizing the relative amplitudes, as shown in 

 the left-hand figure, made the selective fading very bad indeed. The 

 opportunities for producing a result of this nature are rather rare, in 

 fact in our previously mentioned wobble studies it was possible to make 



