Some 30 years ago I had a 4BTV strapped to the chimney of the two story
farmhouse I lived in. The base of the vertial was at about 25 feet. I had
three quarter wave radials on each band laying on the roof or in the case of
40 continuing beyond the roof to some trees. The antenna was put in place
primarily for 40 because I had a triband quad as well.
I would say the antenna played almost as well as a full sized quarter wave
ground plane would on 40. It played extremely well. I can't site any
metrics, but I can certainly say that it was competitive. I had no problems
with tuning the antenna.
One sees lots of comment regarding use of radial fields versus elevated
radials on the reflector and in most cases it is suggested that a vertical
over a well designed system of radials on the ground is superior to the
same vertical over some number of elevated radials. The comparison is
typically with the elevated radials being relatively close to the ground.
I think that the following comment recently made by Tom Rauch W8JI hints at
the answer to Mike's question:question:
"Now if the radials are high enough, say 1/4 to 1/2 wave
above ground, things are OK. But when we put a wire very
close to earth things fall apart."In another practical experience with trap
verticals, NR4M place a five band Butternut trap vertical over a field of
100 fifty foot radials lying on the lawn in an area clear of any
obstructions about fifteen years ago. This antenna also played extremely
well on all bands.
In a third experience we installed a 14AVQ at 100 ft on top of an aircraft
hangar in Keflavik Iceland. We fed the vertical against the metal roof
sheething. This antenna also played well.
Finally my experience with an inverted L for top band fed against eight
elevated radials ten feet off the ground was good, but I know that those
using inverted Ls against good ground level radial systems consistently beat
me in pile-ups.
Based on my experiences and knowing the work that would go into either
configuration for K9MI's friend, I'd tend to do with the "ground plane".
73 de Larry K7SV
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