[Mobile-Portable] Mobile Antennas ground loss

[K7fe at aol.com]

Dave,
Have you ever looked at the relationship between "ground loss" and overall  
antenna length at 40 meters (neglecting loading coil and conductor  losses)?  
As you know, the antenna variables of proximity to ground  producing ground 
loss and the overall length of the radiating element and  resulting efficency 
combine to become the system efficency.   Given  that the maximum vehicle height 
is 13 ft 6 in, if you mount an antenna  about one foot above the ground below 
the bumper, then the maximum antenna  length would be 12 ft 6 in.  One could 
also mount the antenna on the roof  of the vehicle which would lower ground 
loss while shortening the antenna  length to about 8 ft to stay within the max 
vehicle height limit, resulting  in reduced radiator efficency because more coil 
would be  required.  
 
Is there a program to model this and have you any thoughts as to which  
mounting location produces the best overall results? 
 
73, 
Terry, K7FE