strength with a greater maximum range on both radars than did a 

 moderately heavy swell. 



The strength of the sea return is also dependent on several radar 

 characteristics of which the two most important are power Output 

 and antenna height. In the 3-cm. set the high gain or great direc- 

 tivity of the antenna is equivalent to increasing the power output 

 in the direction that the antenna is pointing. Thus for a given 

 power output the higher the frequency the heavier the sea return. 

 The model of radar of the 3-cm. band which was tested had a maxi- 

 mum range of sea return several thousand yards greater than the 

 maximum sea return range of the 10 cm.-band radar. When con- 

 sidering the height of the radar antenna for installation a com- 

 promise would have to be made between area coverage desired and 

 sea return strength that could be allowed. 



It has been seen that the sea return on the scope caused medium 

 sized bergs to go undetected. The gain of the radar set had no 

 effect in helping to distinguish between a berg and sea return. 

 Under these conditions any target which could not be picked up 

 at a range greater than the sea return would never be detected un- 

 less seen visually. This means that present day models of radar 

 would be of little help in preventing collisions v/ith growlers or 

 small bergs in heavy weather and that only in exceptionally smooth 

 weather could radar be relied upon to pick up grovders. 



What then is present to help combat the effect of sea return? 

 There have been several so-called trick circuits developed which 

 help in distinguishing between strong echoes very close together. 

 These circuits are very useful in giving a sharp outline to a shore 

 line or bringing out channel buoys but have not proved satisfactory 

 as yet in combating heavy seas. They remain more as an aid to the 

 navigational use of radar than a safety factor in ice areas. There 

 is hope, however, that methods of "reading through" sea return 

 will be developed just as in underwater sound methods were devel- 

 oped for reducing water noises. Nevertheless, at the present time 

 with standard radar models, sea return on the PPI scope will re- 

 main as the paramount factor in determining the usefulness of 

 radar as a method of detecting ice. Further, the 3-cm. band radar 

 is at the greater disadvantage because of its larger amount of sea 

 clutter on the PPI scope. Thus a vigilant watch must be kept by 

 any vessel, naval or commercial, operating in areas in which ice 

 is likely to be encountered. 



Fog is another important consideration in the Grand Banks area. 

 This area is covered by advection type fog for a large percentage of 

 the time during each ice season. The need for radar in periods of 

 fog is quite obvious. It is very comforting to know that targets 

 can be detected without seeing them visually. But here again a 

 note of caution is advanced. In fog the radar propagation is atten- 



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