Topband: Elevated Radials

[Michael Tope]

----- Original Message ----- 
From: "Ken Brown" <ken.d.brown at hawaiiantel.net>

> Every discussion of elevated radials versus on the ground radials I have 
> seen, so far, just sort of ignores the difference in the length of the 
> vertical radiator. Many of you may be fortunate enough to have a one 
> half wave length support structure, so that you could really compare the 
> performance of quarter wave vertical radiating element with the feed 
> point and radial system a quarter wavelength above the ground, with a 
> quarter wave vertical radiator with it's base and radial system on the 
> ground. However for those of us not so fortunate, who are limited to a 
> total height of less than a quarter wavelength the comparison has to be 
> between two different length vertical radiators, probably with some kind 
> of top loading. I would like to see more discussion that assumes a 
> limited total height, and the vertical section length being reduced by 
> the same amount that the radial system is raised above ground.
> 
> If my radial system were one eight wavelength above ground, the  
> vertical section of  my radiator would be less than zero, or it would be 
> under the radial system.
> 
> Ken N6KB
> 

I have the same problem here, Ken. I think that would be 
an interesting case study. Keep the top of the vertical radiator 
fixed and then raise the base along with a fixed number of radials 
to see if the decrease in radiation resistance gets offset faster or 
slower than the change in ground efficiency. My gut feeling is that 
for a fixed top of vertical radiator height (for H <= 1/8 wavelength), 
you would be better off with radials on the ground. Another 
variation on this would be investigating whether or not gull wing 
radials allow you to have your cake and eat it too (e.g. maximum 
vertical radiator length, but large portion of radials off the ground 
for improved efficiency). Here I suspect the "no free lunch" may 
apply. 

73, Mike W4EF...........................................