HANNA: DESIGN OF TRANSMISSION LOSS EXPERIMENTS 



Talking from a very parochial point of view, from the modeling 

 point of view, if you take a negative reflectivity and put it into a 

 propagation model and you go out a few hundred miles, adding in 2 or 

 3 dB increases of intensity per bounce for the grazing rays, you can 

 get your intensity to arbitrary levels at great range. They are 

 easy to do. 



Dr. S. M. Flatte (University of California College of Santz Cruz) : 

 Why can't you focus a plane wave? 



Mr. Spofford: It will be focused on the bottom, but won't be 

 focused up above. 



Dr. Flatte: No, it can be focused up above the bottom. It just 

 won't happen the next time. If you try and say it will do it many 

 times, it won't. But it can be focused the first time. 



Mr. Spofford: The definition of the reflection coefficient 

 assumes that in a homogeneous medium we have an incident plane wave 

 of unit amplitude. Now, no matter what you put in the bottom, when 

 it comes out again, if you haven't put any absorption in the bottom, 

 it comes out with unit amplitude. 



Dr. Hanna: 1 have the same concern that Chuck has which is 

 that negative reflectivities are rather difficult for me to accommo- 

 date in any of the models I now have. That is not to say those models 

 should not learn how to accommodate to whatever those negative reflec- 

 tivities are trying to tell us. 



The point that I want to make is that there are potential arti- 

 facts in some of those inferred bottom reflectivities produced by 

 the assumed transmission loss along the paths involved. I will feel 

 a lot more comfortable about debating the negative reflectivities and 



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