[Antennas] Car body as a ground plane ??

Sun May 1 16:37:38 EDT 2005

At 12:47 PM 5/1/2005, you wrote:
> > When a 1/4wl vertical is used on a vehicle, we typically think of the
> > car's roof panel (or trunk panel) as the 'ground plane' - completing
> > the rf circuit. With a mobile radio installed in the car, the
> > 'return path' for the signal is through the car's body and frame and
> > then back to the transmitter via either the power return (negative
> > side) and/or through a separate ground strap from the car's frame to
> > the case of the radio.
> >
>UM....not really.........
>>The vehicle makes up half the antenna. The 'return path' is not needed.
>>You can look at a 1/4 wave vertical as a dipole with the whip as one half, 
>and the vehicle as
>the other. At 2mtrs, it is an off center fed dipole. It is more complex 
>than that, but is the
>basic idea.

[snip]
For those who may be interested on the effect of a vehicle's geometry (size 
and shape) can have on VHF antenna performance.
 http://users.adelphia.net/~k6mhe/files/mobile_vhf_ant.pdf
73,
Danny, K6MHE

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