376 BELL SYSTEM TECHNICAL JOURNAL 



In Fig. 27 the MUSA branches were steered at 15 and 22.5 degrees 

 and employed an equahzing delay of 470 microseconds. While the 

 MUSA output is not perfect it is vastly superior to that of the doublet. 

 The tone frequencies and filters are such as to suppress harmonic dis- 

 tortion with the result that the patterns show mainly the selective 

 fading of the fundamental audio frequencies. Note that the funda- 

 mental output nearly disappears in the doublet receiver. In practice 

 this would correspond to violent harmonic distortion of speech or 

 music. 



In addition to the tests and experiments illustrated by the motion 

 picture reproductions in the preceding paragraphs a series of experi- 

 ments were conducted using broadcast transmission on 49 meters from 

 a station at Halifax, Nova Scotia. In these experiments angles and 

 delay differences were measured and compared with the multiple reflec- 

 tion theory. The agreement between measured and predicted values 

 is not only interesting as a study of the ionosphere but constitutes a 

 unique and valuable test of the performance of the MUSA system. 



Observations on VE9IIX, Halifax 



During the course of reception experiments with GSL (BBC, 

 Daventry, 6110 kilocycles) performed as a part of the routine operating 

 program for the MUSA system, a broadcast station appeared on GSL's 

 frequency. This station carried the programs of CHNS, Halifax, 

 Nova Scotia, and was subsequently determined to be an experimental 

 station with the call letters VE9HX located hear Halifax and nearly 

 on the great-circle path from New York to London. The trans- 

 mitting antenna is a half-wave horizontal, one-quarter wave above 

 ground and oriented to radiate in the direction of New York. 



The first experience with this station showed two stable trans- 

 mission paths capable of being separated by the two branches of the 

 MUSA. The delays could be accurately equalized and rather definite 

 correlation was obtained with the multiple "hop" propagation picture. 

 This fact and the additional reason that propagation from England 

 on the same frequency might be compared with the simpler phenomena 

 encountered with Halifax led to the measurements described in the 

 following paragraphs. 



About eleven hours of observation, distributed over fifteen days, are 

 included. The log aimed to record all changes which occurred during 

 an observation period. The procedure was as follows: The two 

 branches of the receiver were steered at the angles indicated by the 

 monitoring oscilloscope. Delay was added to the lower angle branch 

 until the two audio outputs added. The delay setting was usually 



