[Mobile-Portable] Mobile Antennas ground loss

[Tom Bates]

Hi Terry and crew...

Thanks for the change of topic !!

>>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.  

True, but if you then add a cap hat on the end of the shorter stick, less coil turns needed AND less ground loss suffered...win - win.  Anything above a good sized cap hat is mostly ineffective anyway, so why not put the hat right on top?  See how I did it at: http://www.k2bj.com/MOTM_archive/0311MOTM.htm
 
>>Is there a program to model this and have you any thoughts as to which  
mounting location produces the best overall results? 

A couple come to mind...

Check:  http://www.btinternet.com/~g4fgq.regp/#S102

Reg has some really neat programs for shortened verticals / mobile stuff / loading coils.  And, be sure to have a look  at   "Mobile Antenna Analysis" by AA6GL which comes on a disc in one of the Antenna Compendiums ( Vol 4 mebbe ? I have it at home if you need to know for sure ).  That's a fun mobile modeling program to play with.  If you can't find it and get desperate, contact me off list and I'll see if I can help you out with a copy.

73,   Tom   AA1NZ