DIRECTIVITY STEERING FOR FADING REDUCTION 



207 



of the time to make the selective fading worse on the rhombic antenna 

 than on the comparison antenna, but no case has been observed where, 

 at an ordinary rhombic antenna setting, the selective fading was not 

 at least equal to or less than that on the comparison antenna. 



While the cathode ray tube figures indicated some degree of general 

 fading, where all frequencies fade together, it was evident that this 

 type of fading is of far less importance than the selective type of 

 fading, in fact it was rarely noticeable except when the selective fading 

 was almost absent. 



Figure 13 is a photograph of permanent wobble records of selective 



0.4 



TIME IN SECONDS 



Fig. 13 — Oscillographic record of selective fading reduction. The upper trace is 

 proportional to the output of the rhombic antenna, when the angle </> equalled 69 

 degrees, and the center trace is proportional to the output of the half-wave vertical 

 antenna. The lower string was idle. Wobbled carrier from station GBU, April 19, 

 1933, 4:00 p.m., E. S. T. 



fading as recorded by the string oscillograph previously mentioned. 

 The center string was actuated by the signals from the half-wave verti- 

 cal comparison antenna while the rhombus signal was fed to the upper 

 string. The third string was not utilized. The frequency wobble can 

 be seen on close examination and as each small timing division is 0.01 

 second, the audio frequency is recorded. The record has been marked 

 at the wobbled frequency extremities. 



Figures 14, 15, and 16 are sketches of three interesting series of pulse 

 patterns observed on the rhombic and comparison antennas. The 

 three groups reading from left to right show the effects on the individual 

 pulses of the steering of the rhombus, as indicated by the angle 0. 

 The steering achieved at these angles can be seen by referring again 



