[MilCom] Difference AN/PRC-148 Maritime / AN/PRC-148 Urban

[Ken]

While doing some research prior to Santa Claus' arrival I noted that the 
Marine Corps site:
http://www.marcorsyscom.usmc.mil/sites/pmcomm/prc148.asp

Also see: 
http://www2.thalescomminc.com/details.asp?tgs=452490:5132874&cart_id=&item_id=256 
which indicates that over 35K of these units are deployed worlwide with US 
armed forces as well as allies.

Lists two variants for this handheld radio:  Maritime & Urban.. Just 
wondering if anyone knows what the difference is?

This was in relation to "near space"  (Flight level 65K to 325K) utilization 
of communications platforms (UAV's & ballons) which increased this typical 
radio range LOS/7-10 miles to 400 miles.
See:  http://www.military-aerospace-technology.com/article.cfm?DocID=1210

Ken