[TowerTalk] Tuning raised radial verticals

[Jim Brown]

Dan and Gary are two fine engineers, and, as usual, their work is 
excellent. Gary's work was careful to study each element of the array 
alone, with the other elements open circuit to minimize coupling from 
them, but also to study each element as part of the array. This is 
textbook, and exactly right.

Any study of radial systems should also include the extensive and very 
disciplined work of Rudy Severns, N6LF. He has done multiple studies 
that attempt to model what he measures, then measure what he models, 
then model again, and measure again, with each study learning more about 
the various mechanisms at play.  One of the subjects of Rudy's work was 
elevated radial systems, and it was published in two parts in QEX.  It 
is required reading for anyone implementing raised radials.  One of 
Rudy's most important observations was that it is very important to make 
radial currents equal, that the variability of ground under the radials 
can affect that a lot, that 4 radials is minimum and 8 is better, and 
that it helps to tune radials slightly short of a quarter wave.

N6BT has also done a lot of work with verticals and elevated radials. I 
had installed a couple of 160M verticals with radials elevated only 
about 6 ft, and was not getting the gain predicted by the model. He 
advised me that for 160M, radials should be elevated by at least 16 ft. 
I raised mine to an average height of about 20 ft (gull wing style) and 
gain did improve.

http://www.antennasbyn6lf.com/design_of_radial_ground_systems/

73, Jim K9YC

On 9/2/2017 12:41 PM, Bryon Paul Veal NØAH wrote:
> I never have heard of a successful array using raised radials ... so this
> has been a good exercise.  Also strongly agree with tuning the verticals to
> the intended frequency  ..... but this is all with comtek. From the power
> dump port,   I had  300 foot roll of coax coming back to my meter measuring
> the power dump onto the dummy load in my shack!