DEVELOPMENTS IN SHORT-WAVE DIRECTIVE ANTENNAS 681 



the ground and connected to a coupling circuit in such a manner that 

 matched impedances are realized. Although the antenna under con- 

 sideration is intended for the reception of horizontally polarized waves, 

 the same vertical comparison standard has been maintained. 



As previously mentioned, automatic signal recorders of the type 

 shown in Fig. 4, are connected to each antenna. This recorder indi- 

 cates an integrated average signal during each ten-second period, thus 

 removing the wide amplitude excursions due to fading. It is an inter- 

 esting fact that, although the instantaneous fading of two antennas may 

 be different, the average signal over ten seconds usually has correspond- 

 ing rises and falls in amplitude. This effect is so marked that any possi- 

 ble inaccuracies in the timing axis are readily detected, when comparing 

 records. To promote accuracy in amplitude comparisons, only cor- 

 responding peaks or hollows of the curves are used. It is obvious that 

 the employment of steep sides of curves w^ould put a premium on very 

 accurate timing. The relative timing of recorders is usually very good, 

 as their synchronous motors are run by the same a-c power supply. 

 The relative signal strength accuracy of the recorders is better than 

 one db. 



The antenna reported in the following data is an experimental an- 

 tenna, at Holmdel, N. J., shown in the photograph of Fig. 22. This 



Fig. 22 — An experimental horizontal diamond-shaped antenna. 



picture illustrates the extreme simplicity of this type of antenna. The 

 antenna dimensions are the same as those in the previously discussed 

 directive diagrams when used at 16 meters. As has been said so many 

 times before, the gain of the antenna over the standard may be ex- 

 pected to vary with the varying wave directions. The following data 

 are the results of several hundred hours of tests, made at Holmdel, N. 

 J., during the fall and winter months. Three different wave-lengths 



