A SINGLE SIDEBAND MUSA RECEIVING SYSTEM 315 



reflected from the ground at a point ahead of the antenna. If the 

 phase of the induced voltage is to progress uniformly from antenna to 

 antenna it is essential that the ground be homogeneous and flat. For 

 this and other reasons a flat marsh near Manahawkin, N. J. was 

 chosen for the station site. The ground is level to within less than one 

 foot, except where there are inlets, for the entire length of the antenna 

 and for a considerable distance ahead. 



As shown in Fig. 3, in addition to the major lobe caused by the 

 phasing factor there are fourteen minor lobes. The amplitude of 

 the first three starting from a major lobe are approximately 2/3t, 2/57r, 

 2/7x of the major lobe. However, when the major lobe is at a very 

 low or very high angle it is greatly reduced in amplitude by the unit 

 antenna directional characteristic while the adjacent minor lobes on 

 one side may not be reduced to any such extent. Consequently the 

 ratio of the amplitude of the major to minor lobes may be much less 

 than the values given and signals from two or more angles might be 

 received simultaneously with comparable amplitude on the same 

 diversity branch and so defeat the purpose of the system. 



It has been shown by John Stone Stone and others that if the 

 amplitudes of the currents contributed by the various units of the 

 antenna system are tapered in such a manner that the central units 

 contribute more than the end units a reduction in the amplitude of 

 the minor lobes can be obtained. However, this is accompanied by a 

 widening of the major lobe and a reduction in the signal-to-noise im- 

 provement obtained. For antenna systems having only a few units 

 there appears to be a net advantage in tapering but for the sixteen- 

 unit system under discussion a large amount of tapering broadens the 

 major lobe so that it extends over the normal first and possibly second 

 minor lobes. Since the remaining lobes are already of a low enough 

 amplitude to be comparable with those which might be produced by 

 inescapable errors in phase and amplitude of the various unit con- 

 tributions, there appears to be no particular advantage in much taper- 

 ing in this system. Provision has, however, been made to obtain 

 tapering should it ever be found desirable. Under normal conditions 

 all antenna branch amplifiers are operated at the same gain so as to 

 use only the small tapering caused by the losses in transmission lines. 



The antennas are coupled to the transmission lines through metallic 

 core transformers which pass a band from 4,000 kc. to over 20,000 kc. 

 with a loss of less than 1 db. The transformers are equipped with 

 lightning arrestors and arranged so that the total d.c. loop-resistance 

 of the transmission line, antenna, transformer, and antenna termi- 

 nating resistance can be checked from the station. 



