[Antennas] High Take-off Angle of 1/4 wave Vertical??

Wed Mar 23 22:08:55 EST 2005

At 05:05 PM 3/23/2005, David wrote:
>I wonder if a poor radial system increases the radiation
>angle of a 1/4 wave Vertical Ant if the radial system is
>inadequate in some way??

For a ground mounted monopole the launch angle is determined the by ground 
conductivity out *several* wavelengths. (sea water will be at a very low 
angle, dry sandy land will be at a higher angles) A poor radial system 
effects only the efficiency (gain). In other words, going from say a four 
radial system to a 30 radial system will increase the antenna system 
efficiency (gain) but not the take off angle. The can be easily confirmed 
using computer modeling.
>--And, if so, does the radiation angle usually get higher
>as the freq. increases?

When a ground mounted monopole overall height becomes greater than 
5/8-wavelength the higher angle radiation will increase. A 3/4-wavelength 
monopole has substantially more high angle radiation that a 1/4-wavelength 
monopole.
>[snip]

>It occurs to me that this may be happening...and the
>radiation angle gets so high that the USEFUL radiation
>is practically nil...like never able to be received on this
>planet.

Depends upon what you are trying to do. Are you trying for low launch 
angles or NVIS operation?
73,
Danny, K6MHE