206 



ANGLE-OF-ARRIVAL EXPERIMENTS 



BECRS HILL -New YORK PROFILE 

 2 4.08MILCS 



New YORK CITY 

 (140 WEST ST.) 



n 



I 2 3 4 i « 7 S S 10 II 12 13 14 IS l» 17 18 19 20 2 1 22 23 24 



MILES 



BCCR S HILL 



BEERS HILL -DEAL PROriLE 

 12.63 MILES 



Figure 3. Projingation paths, (to])) Beer's Hill to New York and (Ijottom) Beer's Hill to Deal. 



transmitters at both Deal and New York radiate waves 

 polarized at 45 degrees so that either vertical or hori- 

 zontal polarization may be used at the receivers. 



Eesults of angie-of-arrival measurements made dur- 

 ing the summer of 194:4: indicate that on both the Deal 

 and New York circuits the greatest variation of angle 

 of arrival in the horizontal plane was ±1/10 degree. 

 Times were found when the angle of arrival remained 

 as much as 1/10 degree east for short periods on the 

 New York circuit, but for the most part the horizontal 

 angle of arrival normally fluctuated ±1/10 degree 

 from the normal day direction on both the Deal and 

 New York circuits. The maximum variation in the 

 vertical angle of arrival on the direct wave on the 

 New York path has l)een 0.46 degree above that ob- 

 served on a normal day, while the reflected wave has 

 come in as low as 0.17 degree below the normal re- 

 flected wave. (On a normal day the reflected wave on 

 the New York path should be, by calculations, 0.33 

 degree lower than the direct wave.) 



There does not seem to be any correlation between 

 the variation in angle of arrival on the direct wave 

 and the reflected wave. These variations do not as a 

 rule occur together. At the time when the greatest 

 deviation in the reflected wave was present the direct 

 wave was coming in normally. Also, when the direct 

 wave was up 0.46 degree, it was apparently being 

 trapped, and at that time no reflected wave was re- 

 ceived. The greatest spread observed between the 

 direct and reflected wave was 0.7-5 degree (normal 

 0.33 degree). At this time the direct wave was 0.35 

 degree above normal while the reflected wave was 0.07 

 degree below normal. The near proximity of Stateu 

 ishuul to the path normally taken by the reflected 

 \va^•e on the New York path has probably contributed 

 to complexities of the results obtained on this circuit. 



The vertical angle of arrival on the Deal circuit has 

 not \nried as fjreatlv as on the New York circuit. The 



greatest change in angle has been an increase of 0.28 

 degree in the direct wave angle of arrival. The reflected 

 wave is not of sufficient magnitude to be observed on 

 the Deal circuit. 



Height run experiments were conducted to obtain a 

 value for the eft'ective coefficient of reflection for the 

 Deal path. An oscillator was hoisted up and down the 

 175-ft tower at Deal and the resulting received field 

 recorded at Beer's Hill. The field was found to vary 

 3.6 db from maximum to minimum (3 maximum val- 

 ues and 2 minimum values) as the oscillator changed 

 height, which indicates an eff'ective coefficient of reflec- 

 tion of 0.3. This means that the received reflected wave 

 is 5 times weaker than the direct or 14 db down. The 

 distance above ground at which the maximum and 

 minimum were obtained were noted on the receiver 

 record, and from these the height of the efl:ective reflec- 

 tion layer was ol)tained. This height was found to be 

 ap])roximately 100 ft aljove average ground level. 



This experiment is to be repeated when leaves have 

 fallen from the trees to determine if the effective re- 

 flection coefficient or the height of the reflecting layer 

 has changed. 



Eain has been found to influence the X-baud cir- 

 cuits in a manner such as to cause a lowering of the 

 received fields. During very heavy downpours, we have 

 exjjerienced as much as 0.8-clb attenuation per mile 

 of path length on both the paths. We have no way of 

 knowing how much rain was falling over an entire 

 path, but the figure of O.S db per mile represents the 

 maximum value of rain attenuation so far recorded on 

 our circuits. 



Only part-time ob,servations have Jieen made on this 

 project, and the results reported are based ou such 

 observations. It is not known, therefore, if more ex- 

 treme conditions than those reported have existed at 

 times when no observations wei'e being made. 



We expect to continue work on propagation and 



