[Elecraft] Antenna problem / phenomenon

[G3VVT at aol.com]

The answer to the problem is an old one in that it is difficult to get an  HF 
antenna to work with a mag mount due to the low capacitance between the  
magnetic base and the vehicle body.
 
VHF/UHF antenna mounted on a mag mount is OK as the effective low  
capacitance does not present a problem. I even tried a 3 magnet type of mount on  HF 
with the same dismal results. Am told that if you can install a very  short wide 
grounding strap from the mag mount to the vehicle body this can be  the answer 
to the problem, but admit that I was never entirely successful with  this 
either.
 
There seems nothing better than getting a good metallic contact with  the 
vehicle body to get an HF mobile whip to tune and correctly which is what I  had 
to do in the end with a bolted on mount.
 
Bob, G3VVT