A 60-FOOT PARABOLIC ANTENNA FOR PROPAGATION STUDIES 1207 



Table I 



Frequency 



460 mc 

 3.89 kmc 

 9.40 kmc 



Area 



Gain,* 



db 



38.90 

 57.44 

 65.12 



Gain, db Meas. 



37.0 ± 0.1 

 54.6 ± 0.2 



61.1 ± 0.5 



1st Minor 

 lobes 



-23db 

 -18db 



47r 

 * The area gain is defined as 10 log — — , where A is the paraboloid projected 



area, 2,830 square feet. 



incident field at these frequencies due to the remote location of the 

 source. Accordingly, instead of adjusting the feed position for maximum 

 signal level, it was adjusted to give vertical and horizontal radiation 

 patterns having the best possible symmetry, deepest minima, and lowest 

 minor lobes. It was then assumed that this was also the point of maxi- 

 mum gain. At 460 mc the scintillations were so small that the conven- 

 tional technique of adjusting for maximum output was effective. 



A double detection receiver was used for making all measurements. 

 Signal level decibel differences were established by an attenuator in the 

 intermediate frequency (65 mc) channel, and could be determined to an 

 accuracy of dz0.02 db. 



RESULTS 



Carrying out the measuring procedure described above the results 

 given in Table I were obtained. At 460 mc the restricted scanning range 

 did not permit inspection of the minor lobes. 



CONCLUDING REMARKS 



The overall performance of this antenna is considered to be excellent. 

 In general the radiation patterns are clean with satisfactory minor lobe 

 structure. The good performance at 9.4 kmc (61 db gain) is particularly 

 gratifying, since the mechanical tolerance of zt^fe inch is equivalent to 

 itX/7 at this frequency. 



As stated earlier, this antenna was designed to provide a research tool 

 for propagation studies and thus has some features which are neither 

 necessary nor desirable in an antenna intended primarily for communi- 

 cation use. A consideration of the problem of providing a sturdy 60-foot 



